[PATCH v13 00/25] kasan: add software tag-based mode for arm64

[PATCH v13 00/25] kasan: add software tag-based mode for arm64

[Andrey Konovalov]

This patchset adds a new software tag-based mode to KASAN [1].
(Initially this mode was called KHWASAN, but it got renamed,
 see the naming rationale at the end of this section).

The plan is to implement HWASan [2] for the kernel with the incentive,
that it's going to have comparable to KASAN performance, but in the same
time consume much less memory, trading that off for somewhat imprecise
bug detection and being supported only for arm64.

The underlying ideas of the approach used by software tag-based KASAN are:

1. By using the Top Byte Ignore (TBI) arm64 CPU feature, we can store
   pointer tags in the top byte of each kernel pointer.

2. Using shadow memory, we can store memory tags for each chunk of kernel
   memory.

3. On each memory allocation, we can generate a random tag, embed it into
   the returned pointer and set the memory tags that correspond to this
   chunk of memory to the same value.

4. By using compiler instrumentation, before each memory access we can add
   a check that the pointer tag matches the tag of the memory that is being
   accessed.

5. On a tag mismatch we report an error.

With this patchset the existing KASAN mode gets renamed to generic KASAN,
with the word "generic" meaning that the implementation can be supported
by any architecture as it is purely software.

The new mode this patchset adds is called software tag-based KASAN. The
word "tag-based" refers to the fact that this mode uses tags embedded into
the top byte of kernel pointers and the TBI arm64 CPU feature that allows
to dereference such pointers. The word "software" here means that shadow
memory manipulation and tag checking on pointer dereference is done in
software. As it is the only tag-based implementation right now, "software
tag-based" KASAN is sometimes referred to as simply "tag-based" in this
patchset.

A potential expansion of this mode is a hardware tag-based mode, which would
use hardware memory tagging support (announced by Arm [3]) instead of
compiler instrumentation and manual shadow memory manipulation.

Same as generic KASAN, software tag-based KASAN is strictly a debugging
feature.

[1] https://www.kernel.org/doc/html/latest/dev-tools/kasan.html

[2] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html

[3] https://community.arm.com/processors/b/blog/posts/arm-a-profile-architecture-2018-developments-armv85a


====== Rationale

On mobile devices generic KASAN's memory usage is significant problem. One
of the main reasons to have tag-based KASAN is to be able to perform a
similar set of checks as the generic one does, but with lower memory
requirements.

Comment from Vishwath Mohan <vishwath@google.com>:

I don't have data on-hand, but anecdotally both ASAN and KASAN have proven
problematic to enable for environments that don't tolerate the increased
memory pressure well. This includes,
(a) Low-memory form factors - Wear, TV, Things, lower-tier phones like Go,
(c) Connected components like Pixel's visual core [1].

These are both places I'd love to have a low(er) memory footprint option at
my disposal.

Comment from Evgenii Stepanov <eugenis@google.com>:

Looking at a live Android device under load, slab (according to
/proc/meminfo) + kernel stack take 8-10% available RAM (~350MB). KASAN's
overhead of 2x - 3x on top of it is not insignificant.

Not having this overhead enables near-production use - ex. running
KASAN/KHWASAN kernel on a personal, daily-use device to catch bugs that do
not reproduce in test configuration. These are the ones that often cost
the most engineering time to track down.

CPU overhead is bad, but generally tolerable. RAM is critical, in our
experience. Once it gets low enough, OOM-killer makes your life miserable.

[1] https://www.blog.google/products/pixel/pixel-visual-core-image-processing-and-machine-learning-pixel-2/


====== Technical details

Software tag-based KASAN mode is implemented in a very similar way to the
generic one. This patchset essentially does the following:

1. TCR_TBI1 is set to enable Top Byte Ignore.

2. Shadow memory is used (with a different scale, 1:16, so each shadow
   byte corresponds to 16 bytes of kernel memory) to store memory tags.

3. All slab objects are aligned to shadow scale, which is 16 bytes.

4. All pointers returned from the slab allocator are tagged with a random
   tag and the corresponding shadow memory is poisoned with the same value.

5. Compiler instrumentation is used to insert tag checks. Either by
   calling callbacks or by inlining them (CONFIG_KASAN_OUTLINE and
   CONFIG_KASAN_INLINE flags are reused).

6. When a tag mismatch is detected in callback instrumentation mode
   KASAN simply prints a bug report. In case of inline instrumentation,
   clang inserts a brk instruction, and KASAN has it's own brk handler,
   which reports the bug.

7. The memory in between slab objects is marked with a reserved tag, and
   acts as a redzone.

8. When a slab object is freed it's marked with a reserved tag.

Bug detection is imprecise for two reasons:

1. We won't catch some small out-of-bounds accesses, that fall into the
   same shadow cell, as the last byte of a slab object.

2. We only have 1 byte to store tags, which means we have a 1/256
   probability of a tag match for an incorrect access (actually even
   slightly less due to reserved tag values).

Despite that there's a particular type of bugs that tag-based KASAN can
detect compared to generic KASAN: use-after-free after the object has been
allocated by someone else.


====== Testing

Some kernel developers voiced a concern that changing the top byte of
kernel pointers may lead to subtle bugs that are difficult to discover.
To address this concern deliberate testing has been performed.

It doesn't seem feasible to do some kind of static checking to find
potential issues with pointer tagging, so a dynamic approach was taken.
All pointer comparisons/subtractions have been instrumented in an LLVM
compiler pass and a kernel module that would print a bug report whenever
two pointers with different tags are being compared/subtracted (ignoring
comparisons with NULL pointers and with pointers obtained by casting an
error code to a pointer type) has been used. Then the kernel has been
booted in QEMU and on an Odroid C2 board and syzkaller has been run.

This yielded the following results.

The two places that look interesting are:

is_vmalloc_addr in include/linux/mm.h
is_kernel_rodata in mm/util.c

Here we compare a pointer with some fixed untagged values to make sure
that the pointer lies in a particular part of the kernel address space.
Since tag-based KASAN doesn't add tags to pointers that belong to rodata
or vmalloc regions, this should work as is. To make sure debug checks to
those two functions that check that the result doesn't change whether
we operate on pointers with or without untagging has been added.

A few other cases that don't look that interesting:

Comparing pointers to achieve unique sorting order of pointee objects
(e.g. sorting locks addresses before performing a double lock):

tty_ldisc_lock_pair_timeout in drivers/tty/tty_ldisc.c
pipe_double_lock in fs/pipe.c
unix_state_double_lock in net/unix/af_unix.c
lock_two_nondirectories in fs/inode.c
mutex_lock_double in kernel/events/core.c

ep_cmp_ffd in fs/eventpoll.c
fsnotify_compare_groups fs/notify/mark.c

Nothing needs to be done here, since the tags embedded into pointers
don't change, so the sorting order would still be unique.

Checks that a pointer belongs to some particular allocation:

is_sibling_entry in lib/radix-tree.c
object_is_on_stack in include/linux/sched/task_stack.h

Nothing needs to be done here either, since two pointers can only belong
to the same allocation if they have the same tag.

Overall, since the kernel boots and works, there are no critical bugs.
As for the rest, the traditional kernel testing way (use until fails) is
the only one that looks feasible.

Another point here is that tag-based KASAN is available under a separate
config option that needs to be deliberately enabled. Even though it might
be used in a "near-production" environment to find bugs that are not found
during fuzzing or running tests, it is still a debug tool.


====== Benchmarks

The following numbers were collected on Odroid C2 board. Both generic and
tag-based KASAN were used in inline instrumentation mode.

Boot time [1]:
* ~1.7 sec for clean kernel
* ~5.0 sec for generic KASAN
* ~5.0 sec for tag-based KASAN

Network performance [2]:
* 8.33 Gbits/sec for clean kernel
* 3.17 Gbits/sec for generic KASAN
* 2.85 Gbits/sec for tag-based KASAN

Slab memory usage after boot [3]:
* ~40 kb for clean kernel
* ~105 kb (~260% overhead) for generic KASAN
* ~47 kb (~20% overhead) for tag-based KASAN

KASAN memory overhead consists of three main parts:
1. Increased slab memory usage due to redzones.
2. Shadow memory (the whole reserved once during boot).
3. Quaratine (grows gradually until some preset limit; the more the limit,
   the more the chance to detect a use-after-free).

Comparing tag-based vs generic KASAN for each of these points:
1. 20% vs 260% overhead.
2. 1/16th vs 1/8th of physical memory.
3. Tag-based KASAN doesn't require quarantine.

[1] Time before the ext4 driver is initialized.
[2] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`.
[3] Measured as `cat /proc/meminfo | grep Slab`.


====== Some notes

A few notes:

1. The patchset can be found here:
   https://github.com/xairy/kasan-prototype/tree/khwasan

2. Building requires a recent Clang version (7.0.0 or later).

3. Stack instrumentation is not supported yet and will be added later.


====== Changes

Changes in v13:
- Fixed Kconfig KASAN options dependencies to forbid enabling CONFIG_KASAN
  without one of the modes.
- Select HAVE_ARCH_KASAN_SW_TAGS if HAVE_ARCH_KASAN in arm64 Kconfig.
- Reverted adding __arm64_skip_faulting_instruction.
- Rebased onto 4.20-rc4+ (cf76c364).

Changes in v12:
- Rebased onto ef78e5ec (4.20-rc4+).
- Used u64 instead of __u64 in arch/arm64/include/asm/memory.h as it isn't
  a UAPI header.
- Moved the untagged_addr() macro down into the #ifndef __ASSEMBLY__
  block, after we include <linux/bitops.h>, which is necessary for
  sign_extend64().
- New patch: "kasan, arm64: select HAVE_ARCH_KASAN_SW_TAGS", that selects
  HAVE_ARCH_KASAN_SW_TAGS for arm64 after all the necessary infrastructure
  code is added.
- Minor style fixes.

Changes in v11:
- Rebased onto 9ff01193 (4.20-rc3).
- Moved KASAN_SHADOW_SCALE_SHIFT definition to arch/arm64/Makefile.
- Added and used CC_HAS_KASAN_GENERIC and CC_HAS_KASAN_SW_TAGS configs to
  detect compiler support.
- New patch: "kasan: rename kasan_zero_page to kasan_early_shadow_page".
- New patch: "arm64: move untagged_addr macro from uaccess.h to memory.h".
- Renamed KASAN_SET_TAG/... macros in arch/arm64/include/asm/memory.h to
  __tag_set/... and reused them later in KASAN core code instead of
  redefining.
- Removed tag reset from the __kimg_to_phys() macro.
- Fixed tagged pointer handling in arm64 fault handling logic.

Changes in v10:
- Rebased onto 65102238 (4.20-rc1).
- Don't ignore kasan_kmalloc() return valued in kmem_cache_alloc_trace()
  and kmem_cache_alloc_node_trace() in include/linux/slab.h.
- New patch: don't ignore kasan_kmalloc return value in
  early_kmem_cache_node_alloc.
- New patch: added __must_check annotations to KASAN hooks that assign
  tags.
- Changed KASAN clang version requirement to 7.0.0 (as we need rL329612).
- Moved __no_sanitize_address definition from compiler_attributes.h to
  compiler-gcc.h and compiler-clang.h.

Changes in v9:
- Fixed kasan_init_slab_obj() hook when KASAN is disabled.
- Added assign_tag() function that preassigns tags for caches with
  constructors.
- Fixed KASAN_TAG_MASK redefinition in include/linux/mm.h vs
  mm/kasan/kasan.h.

Changes in v8:
- Rebased onto 7876320f (4.19-rc4).
- Renamed KHWASAN to software tag-based KASAN (see the top of the cover
  letter for details).
- Explicitly called tag-based KASAN a debug tool.
- Reused kasan_init_slab_obj() callback to preassign tags to caches
  without constructors, remove khwasan_preset_sl(u/a)b_tag().
- Moved move obj_to_index to include/linux/slab_def.h from mm/slab.c.
- Moved cache->s_mem untagging to alloc_slabmgmt() for SLAB.
- Fixed check_memory_region() to correctly handle user memory accesses and
  size == 0 case.
- Merged __no_sanitize_hwaddress into __no_sanitize_address.
- Defined KASAN_SET_TAG and KASAN_RESET_TAG macros for non KASAN builds to
  avoid duplication of __kimg_to_phys, _virt_addr_is_linear and
  page_to_virt macros.
- Fixed and simplified find_first_bad_addr for generic KASAN.
- Use non symbolized example KASAN report in documentation.
- Mention clang version requirements for both KASAN modes in the Kconfig
  options and in the documentation.
- Various small fixes.

Version v7 got accidentally skipped.

Changes in v6:
- Rebased onto 050cdc6c (4.19-rc1+).
- Added notes regarding patchset testing into the cover letter.

Changes in v5:
- Rebased onto 1ffaddd029 (4.18-rc8).
- Preassign tags for objects from caches with constructors and
  SLAB_TYPESAFE_BY_RCU caches.
- Fix SLAB allocator support by untagging page->s_mem in
  kasan_poison_slab().
- Performed dynamic testing to find potential places where pointer tagging
  might result in bugs [1].
- Clarified and fixed memory usage benchmarks in the cover letter.
- Added a rationale for having KHWASAN to the cover letter.

Changes in v4:
- Fixed SPDX comment style in mm/kasan/kasan.h.
- Fixed mm/kasan/kasan.h changes being included in a wrong patch.
- Swapped "khwasan, arm64: fix up fault handling logic" and "khwasan: add
  tag related helper functions" patches order.
- Rebased onto 6f0d349d (4.18-rc2+).

Changes in v3:
- Minor documentation fixes.
- Fixed CFLAGS variable name in KASAN makefile.
- Added a "SPDX-License-Identifier: GPL-2.0" line to all source files
  under mm/kasan.
- Rebased onto 81e97f013 (4.18-rc1+).

Changes in v2:
- Changed kmalloc_large_node_hook to return tagged pointer instead of
  using an output argument.
- Fix checking whether -fsanitize=hwaddress is supported by the compiler.
- Removed duplication of -fno-builtin for KASAN and KHWASAN.
- Removed {} block for one line for_each_possible_cpu loop.
- Made set_track() static inline as it is used only in common.c.
- Moved optimal_redzone() to common.c.
- Fixed using tagged pointer for shadow calculation in
  kasan_unpoison_shadow().
- Restored setting cache->align in kasan_cache_create(), which was
  accidentally lost.
- Simplified __kasan_slab_free(), kasan_alloc_pages() and kasan_kmalloc().
- Removed tagging from kasan_kmalloc_large().
- Added page_kasan_tag_reset() to kasan_poison_slab() and removed
  !PageSlab() check from page_to_virt.
- Reset pointer tag in _virt_addr_is_linear.
- Set page tag for each page when multiple pages are allocated or freed.
- Added a comment as to why we ignore cma allocated pages.

Changes in v1:
- Rebased onto 4.17-rc4.
- Updated benchmarking stats.
- Documented compiler version requirements, memory usage and slowdown.
- Dropped kvm patches, as clang + arm64 + kvm is completely broken [1].

Changes in RFC v3:
- Renamed CONFIG_KASAN_CLASSIC and CONFIG_KASAN_TAGS to
  CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW respectively.
- Switch to -fsanitize=kernel-hwaddress instead of -fsanitize=hwaddress.
- Removed unnecessary excessive shadow initialization.
- Removed khwasan_enabled flag (it's not needed since KHWASAN is
  initialized before any slab caches are used).
- Split out kasan_report.c and khwasan_report.c from report.c.
- Moved more common KASAN and KHWASAN functions to common.c.
- Added tagging to pagealloc.
- Rebased onto 4.17-rc1.
- Temporarily dropped patch that adds kvm support (arm64 + kvm + clang
  combo is broken right now [2]).

Changes in RFC v2:
- Removed explicit casts to u8 * for kasan_mem_to_shadow() calls.
- Introduced KASAN_TCR_FLAGS for setting the TCR_TBI1 flag.
- Added a comment regarding the non-atomic RMW sequence in
  khwasan_random_tag().
- Made all tag related functions accept const void *.
- Untagged pointers in __kimg_to_phys, which is used by virt_to_phys.
- Untagged pointers in show_ptr in fault handling logic.
- Untagged pointers passed to KVM.
- Added two reserved tag values: 0xFF and 0xFE.
- Used the reserved tag 0xFF to disable validity checking (to resolve the
  issue with pointer tag being lost after page_address + kmap usage).
- Used the reserved tag 0xFE to mark redzones and freed objects.
- Added mnemonics for esr manipulation in KHWASAN brk handler.
- Added a comment about the -recover flag.
- Some minor cleanups and fixes.
- Rebased onto 3215b9d5 (4.16-rc6+).
- Tested on real hardware (Odroid C2 board).
- Added better benchmarks.

[1] https://lkml.org/lkml/2018/7/18/765
[2] https://lkml.org/lkml/2018/4/19/775

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Andrey Konovalov (25):
  kasan, mm: change hooks signatures
  kasan, slub: handle pointer tags in early_kmem_cache_node_alloc
  kasan: move common generic and tag-based code to common.c
  kasan: rename source files to reflect the new naming scheme
  kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS
  kasan, arm64: adjust shadow size for tag-based mode
  kasan: rename kasan_zero_page to kasan_early_shadow_page
  kasan: initialize shadow to 0xff for tag-based mode
  arm64: move untagged_addr macro from uaccess.h to memory.h
  kasan: add tag related helper functions
  kasan, arm64: untag address in _virt_addr_is_linear
  kasan: preassign tags to objects with ctors or SLAB_TYPESAFE_BY_RCU
  kasan, arm64: fix up fault handling logic
  kasan, arm64: enable top byte ignore for the kernel
  kasan, mm: perform untagged pointers comparison in krealloc
  kasan: split out generic_report.c from report.c
  kasan: add bug reporting routines for tag-based mode
  mm: move obj_to_index to include/linux/slab_def.h
  kasan: add hooks implementation for tag-based mode
  kasan, arm64: add brk handler for inline instrumentation
  kasan, mm, arm64: tag non slab memory allocated via pagealloc
  kasan: add __must_check annotations to kasan hooks
  kasan, arm64: select HAVE_ARCH_KASAN_SW_TAGS
  kasan: update documentation
  kasan: add SPDX-License-Identifier mark to source files

 Documentation/dev-tools/kasan.rst      | 232 +++++----
 arch/arm64/Kconfig                     |   1 +
 arch/arm64/Makefile                    |  11 +-
 arch/arm64/include/asm/brk-imm.h       |   2 +
 arch/arm64/include/asm/kasan.h         |   8 +-
 arch/arm64/include/asm/memory.h        |  42 +-
 arch/arm64/include/asm/pgtable-hwdef.h |   1 +
 arch/arm64/include/asm/uaccess.h       |   7 -
 arch/arm64/kernel/traps.c              |  60 +++
 arch/arm64/mm/fault.c                  |  31 +-
 arch/arm64/mm/kasan_init.c             |  56 ++-
 arch/arm64/mm/proc.S                   |   8 +-
 arch/s390/mm/dump_pagetables.c         |  17 +-
 arch/s390/mm/kasan_init.c              |  33 +-
 arch/x86/mm/dump_pagetables.c          |  11 +-
 arch/x86/mm/kasan_init_64.c            |  55 ++-
 arch/xtensa/mm/kasan_init.c            |  18 +-
 include/linux/compiler-clang.h         |   6 +-
 include/linux/compiler-gcc.h           |   6 +
 include/linux/compiler_attributes.h    |  13 -
 include/linux/kasan.h                  | 101 +++-
 include/linux/mm.h                     |  29 ++
 include/linux/page-flags-layout.h      |  10 +
 include/linux/slab.h                   |   4 +-
 include/linux/slab_def.h               |  13 +
 lib/Kconfig.kasan                      |  98 +++-
 mm/cma.c                               |  11 +
 mm/kasan/Makefile                      |  15 +-
 mm/kasan/{kasan.c => common.c}         | 656 +++++++++----------------
 mm/kasan/generic.c                     | 344 +++++++++++++
 mm/kasan/generic_report.c              | 153 ++++++
 mm/kasan/{kasan_init.c => init.c}      |  71 +--
 mm/kasan/kasan.h                       |  59 ++-
 mm/kasan/quarantine.c                  |   1 +
 mm/kasan/report.c                      | 272 +++-------
 mm/kasan/tags.c                        | 161 ++++++
 mm/kasan/tags_report.c                 |  58 +++
 mm/page_alloc.c                        |   1 +
 mm/slab.c                              |  29 +-
 mm/slab.h                              |   2 +-
 mm/slab_common.c                       |   6 +-
 mm/slub.c                              |  51 +-
 scripts/Makefile.kasan                 |  53 +-
 43 files changed, 1817 insertions(+), 999 deletions(-)
 rename mm/kasan/{kasan.c => common.c} (59%)
 create mode 100644 mm/kasan/generic.c
 create mode 100644 mm/kasan/generic_report.c
 rename mm/kasan/{kasan_init.c => init.c} (82%)
 create mode 100644 mm/kasan/tags.c
 create mode 100644 mm/kasan/tags_report.c

-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 01/25] kasan, mm: change hooks signatures

[Andrey Konovalov]

Tag-based KASAN changes the value of the top byte of pointers returned
from the kernel allocation functions (such as kmalloc). This patch updates
KASAN hooks signatures and their usage in SLAB and SLUB code to reflect
that.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/kasan.h | 43 +++++++++++++++++++++++++++++--------------
 include/linux/slab.h  |  4 ++--
 mm/kasan/kasan.c      | 30 ++++++++++++++++++------------
 mm/slab.c             | 12 ++++++------
 mm/slab.h             |  2 +-
 mm/slab_common.c      |  4 ++--
 mm/slub.c             | 15 +++++++--------
 7 files changed, 65 insertions(+), 45 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 46aae129917c..52c86a568a4e 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -51,16 +51,16 @@ void kasan_cache_shutdown(struct kmem_cache *cache);
 void kasan_poison_slab(struct page *page);
 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
 void kasan_poison_object_data(struct kmem_cache *cache, void *object);
-void kasan_init_slab_obj(struct kmem_cache *cache, const void *object);
+void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object);
 
-void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags);
+void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags);
 void kasan_kfree_large(void *ptr, unsigned long ip);
 void kasan_poison_kfree(void *ptr, unsigned long ip);
-void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size,
+void *kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size,
 		  gfp_t flags);
-void kasan_krealloc(const void *object, size_t new_size, gfp_t flags);
+void *kasan_krealloc(const void *object, size_t new_size, gfp_t flags);
 
-void kasan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags);
+void *kasan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags);
 bool kasan_slab_free(struct kmem_cache *s, void *object, unsigned long ip);
 
 struct kasan_cache {
@@ -105,19 +105,34 @@ static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
 					void *object) {}
 static inline void kasan_poison_object_data(struct kmem_cache *cache,
 					void *object) {}
-static inline void kasan_init_slab_obj(struct kmem_cache *cache,
-				const void *object) {}
+static inline void *kasan_init_slab_obj(struct kmem_cache *cache,
+				const void *object)
+{
+	return (void *)object;
+}
 
-static inline void kasan_kmalloc_large(void *ptr, size_t size, gfp_t flags) {}
+static inline void *kasan_kmalloc_large(void *ptr, size_t size, gfp_t flags)
+{
+	return ptr;
+}
 static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
 static inline void kasan_poison_kfree(void *ptr, unsigned long ip) {}
-static inline void kasan_kmalloc(struct kmem_cache *s, const void *object,
-				size_t size, gfp_t flags) {}
-static inline void kasan_krealloc(const void *object, size_t new_size,
-				 gfp_t flags) {}
+static inline void *kasan_kmalloc(struct kmem_cache *s, const void *object,
+				size_t size, gfp_t flags)
+{
+	return (void *)object;
+}
+static inline void *kasan_krealloc(const void *object, size_t new_size,
+				 gfp_t flags)
+{
+	return (void *)object;
+}
 
-static inline void kasan_slab_alloc(struct kmem_cache *s, void *object,
-				   gfp_t flags) {}
+static inline void *kasan_slab_alloc(struct kmem_cache *s, void *object,
+				   gfp_t flags)
+{
+	return object;
+}
 static inline bool kasan_slab_free(struct kmem_cache *s, void *object,
 				   unsigned long ip)
 {
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 918f374e7156..351ac48dabc4 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -444,7 +444,7 @@ static __always_inline void *kmem_cache_alloc_trace(struct kmem_cache *s,
 {
 	void *ret = kmem_cache_alloc(s, flags);
 
-	kasan_kmalloc(s, ret, size, flags);
+	ret = kasan_kmalloc(s, ret, size, flags);
 	return ret;
 }
 
@@ -455,7 +455,7 @@ kmem_cache_alloc_node_trace(struct kmem_cache *s,
 {
 	void *ret = kmem_cache_alloc_node(s, gfpflags, node);
 
-	kasan_kmalloc(s, ret, size, gfpflags);
+	ret = kasan_kmalloc(s, ret, size, gfpflags);
 	return ret;
 }
 #endif /* CONFIG_TRACING */
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index c3bd5209da38..55deff17a4d9 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -474,20 +474,22 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 	return (void *)object + cache->kasan_info.free_meta_offset;
 }
 
-void kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
+void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 {
 	struct kasan_alloc_meta *alloc_info;
 
 	if (!(cache->flags & SLAB_KASAN))
-		return;
+		return (void *)object;
 
 	alloc_info = get_alloc_info(cache, object);
 	__memset(alloc_info, 0, sizeof(*alloc_info));
+
+	return (void *)object;
 }
 
-void kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
+void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
 {
-	kasan_kmalloc(cache, object, cache->object_size, flags);
+	return kasan_kmalloc(cache, object, cache->object_size, flags);
 }
 
 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
@@ -528,7 +530,7 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 	return __kasan_slab_free(cache, object, ip, true);
 }
 
-void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
+void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 		   gfp_t flags)
 {
 	unsigned long redzone_start;
@@ -538,7 +540,7 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 		quarantine_reduce();
 
 	if (unlikely(object == NULL))
-		return;
+		return NULL;
 
 	redzone_start = round_up((unsigned long)(object + size),
 				KASAN_SHADOW_SCALE_SIZE);
@@ -551,10 +553,12 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 
 	if (cache->flags & SLAB_KASAN)
 		set_track(&get_alloc_info(cache, object)->alloc_track, flags);
+
+	return (void *)object;
 }
 EXPORT_SYMBOL(kasan_kmalloc);
 
-void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
+void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 {
 	struct page *page;
 	unsigned long redzone_start;
@@ -564,7 +568,7 @@ void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 		quarantine_reduce();
 
 	if (unlikely(ptr == NULL))
-		return;
+		return NULL;
 
 	page = virt_to_page(ptr);
 	redzone_start = round_up((unsigned long)(ptr + size),
@@ -574,21 +578,23 @@ void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 	kasan_unpoison_shadow(ptr, size);
 	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 		KASAN_PAGE_REDZONE);
+
+	return (void *)ptr;
 }
 
-void kasan_krealloc(const void *object, size_t size, gfp_t flags)
+void *kasan_krealloc(const void *object, size_t size, gfp_t flags)
 {
 	struct page *page;
 
 	if (unlikely(object == ZERO_SIZE_PTR))
-		return;
+		return ZERO_SIZE_PTR;
 
 	page = virt_to_head_page(object);
 
 	if (unlikely(!PageSlab(page)))
-		kasan_kmalloc_large(object, size, flags);
+		return kasan_kmalloc_large(object, size, flags);
 	else
-		kasan_kmalloc(page->slab_cache, object, size, flags);
+		return kasan_kmalloc(page->slab_cache, object, size, flags);
 }
 
 void kasan_poison_kfree(void *ptr, unsigned long ip)
diff --git a/mm/slab.c b/mm/slab.c
index 2a5654bb3b3f..26f60a22e5e0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3551,7 +3551,7 @@ void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 {
 	void *ret = slab_alloc(cachep, flags, _RET_IP_);
 
-	kasan_slab_alloc(cachep, ret, flags);
+	ret = kasan_slab_alloc(cachep, ret, flags);
 	trace_kmem_cache_alloc(_RET_IP_, ret,
 			       cachep->object_size, cachep->size, flags);
 
@@ -3617,7 +3617,7 @@ kmem_cache_alloc_trace(struct kmem_cache *cachep, gfp_t flags, size_t size)
 
 	ret = slab_alloc(cachep, flags, _RET_IP_);
 
-	kasan_kmalloc(cachep, ret, size, flags);
+	ret = kasan_kmalloc(cachep, ret, size, flags);
 	trace_kmalloc(_RET_IP_, ret,
 		      size, cachep->size, flags);
 	return ret;
@@ -3641,7 +3641,7 @@ void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid)
 {
 	void *ret = slab_alloc_node(cachep, flags, nodeid, _RET_IP_);
 
-	kasan_slab_alloc(cachep, ret, flags);
+	ret = kasan_slab_alloc(cachep, ret, flags);
 	trace_kmem_cache_alloc_node(_RET_IP_, ret,
 				    cachep->object_size, cachep->size,
 				    flags, nodeid);
@@ -3660,7 +3660,7 @@ void *kmem_cache_alloc_node_trace(struct kmem_cache *cachep,
 
 	ret = slab_alloc_node(cachep, flags, nodeid, _RET_IP_);
 
-	kasan_kmalloc(cachep, ret, size, flags);
+	ret = kasan_kmalloc(cachep, ret, size, flags);
 	trace_kmalloc_node(_RET_IP_, ret,
 			   size, cachep->size,
 			   flags, nodeid);
@@ -3681,7 +3681,7 @@ __do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
 	if (unlikely(ZERO_OR_NULL_PTR(cachep)))
 		return cachep;
 	ret = kmem_cache_alloc_node_trace(cachep, flags, node, size);
-	kasan_kmalloc(cachep, ret, size, flags);
+	ret = kasan_kmalloc(cachep, ret, size, flags);
 
 	return ret;
 }
@@ -3719,7 +3719,7 @@ static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
 		return cachep;
 	ret = slab_alloc(cachep, flags, caller);
 
-	kasan_kmalloc(cachep, ret, size, flags);
+	ret = kasan_kmalloc(cachep, ret, size, flags);
 	trace_kmalloc(caller, ret,
 		      size, cachep->size, flags);
 
diff --git a/mm/slab.h b/mm/slab.h
index 58c6c1c2a78e..4190c24ef0e9 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -441,7 +441,7 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
 
 		kmemleak_alloc_recursive(object, s->object_size, 1,
 					 s->flags, flags);
-		kasan_slab_alloc(s, object, flags);
+		p[i] = kasan_slab_alloc(s, object, flags);
 	}
 
 	if (memcg_kmem_enabled())
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 7eb8dc136c1c..5f3504e26d4c 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1204,7 +1204,7 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
 	page = alloc_pages(flags, order);
 	ret = page ? page_address(page) : NULL;
 	kmemleak_alloc(ret, size, 1, flags);
-	kasan_kmalloc_large(ret, size, flags);
+	ret = kasan_kmalloc_large(ret, size, flags);
 	return ret;
 }
 EXPORT_SYMBOL(kmalloc_order);
@@ -1482,7 +1482,7 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size,
 		ks = ksize(p);
 
 	if (ks >= new_size) {
-		kasan_krealloc((void *)p, new_size, flags);
+		p = kasan_krealloc((void *)p, new_size, flags);
 		return (void *)p;
 	}
 
diff --git a/mm/slub.c b/mm/slub.c
index e3629cd7aff1..fdd4a86aa882 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1372,10 +1372,10 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node,
  * Hooks for other subsystems that check memory allocations. In a typical
  * production configuration these hooks all should produce no code at all.
  */
-static inline void kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
+static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
 {
 	kmemleak_alloc(ptr, size, 1, flags);
-	kasan_kmalloc_large(ptr, size, flags);
+	return kasan_kmalloc_large(ptr, size, flags);
 }
 
 static __always_inline void kfree_hook(void *x)
@@ -2768,7 +2768,7 @@ void *kmem_cache_alloc_trace(struct kmem_cache *s, gfp_t gfpflags, size_t size)
 {
 	void *ret = slab_alloc(s, gfpflags, _RET_IP_);
 	trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags);
-	kasan_kmalloc(s, ret, size, gfpflags);
+	ret = kasan_kmalloc(s, ret, size, gfpflags);
 	return ret;
 }
 EXPORT_SYMBOL(kmem_cache_alloc_trace);
@@ -2796,7 +2796,7 @@ void *kmem_cache_alloc_node_trace(struct kmem_cache *s,
 	trace_kmalloc_node(_RET_IP_, ret,
 			   size, s->size, gfpflags, node);
 
-	kasan_kmalloc(s, ret, size, gfpflags);
+	ret = kasan_kmalloc(s, ret, size, gfpflags);
 	return ret;
 }
 EXPORT_SYMBOL(kmem_cache_alloc_node_trace);
@@ -3784,7 +3784,7 @@ void *__kmalloc(size_t size, gfp_t flags)
 
 	trace_kmalloc(_RET_IP_, ret, size, s->size, flags);
 
-	kasan_kmalloc(s, ret, size, flags);
+	ret = kasan_kmalloc(s, ret, size, flags);
 
 	return ret;
 }
@@ -3801,8 +3801,7 @@ static void *kmalloc_large_node(size_t size, gfp_t flags, int node)
 	if (page)
 		ptr = page_address(page);
 
-	kmalloc_large_node_hook(ptr, size, flags);
-	return ptr;
+	return kmalloc_large_node_hook(ptr, size, flags);
 }
 
 void *__kmalloc_node(size_t size, gfp_t flags, int node)
@@ -3829,7 +3828,7 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
 
 	trace_kmalloc_node(_RET_IP_, ret, size, s->size, flags, node);
 
-	kasan_kmalloc(s, ret, size, flags);
+	ret = kasan_kmalloc(s, ret, size, flags);
 
 	return ret;
 }
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 02/25] kasan, slub: handle pointer tags in early_kmem_cache_node_alloc

[Andrey Konovalov]

The previous patch updated KASAN hooks signatures and their usage in SLAB
and SLUB code, except for the early_kmem_cache_node_alloc function. This
patch handles that function separately, as it requires to reorder some of
the initialization code to correctly propagate a tagged pointer in case a
tag is assigned by kasan_kmalloc.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/slub.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index fdd4a86aa882..8561a32910dd 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3364,16 +3364,16 @@ static void early_kmem_cache_node_alloc(int node)
 
 	n = page->freelist;
 	BUG_ON(!n);
-	page->freelist = get_freepointer(kmem_cache_node, n);
-	page->inuse = 1;
-	page->frozen = 0;
-	kmem_cache_node->node[node] = n;
 #ifdef CONFIG_SLUB_DEBUG
 	init_object(kmem_cache_node, n, SLUB_RED_ACTIVE);
 	init_tracking(kmem_cache_node, n);
 #endif
-	kasan_kmalloc(kmem_cache_node, n, sizeof(struct kmem_cache_node),
+	n = kasan_kmalloc(kmem_cache_node, n, sizeof(struct kmem_cache_node),
 		      GFP_KERNEL);
+	page->freelist = get_freepointer(kmem_cache_node, n);
+	page->inuse = 1;
+	page->frozen = 0;
+	kmem_cache_node->node[node] = n;
 	init_kmem_cache_node(n);
 	inc_slabs_node(kmem_cache_node, node, page->objects);
 
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 03/25] kasan: move common generic and tag-based code to common.c

[Andrey Konovalov]

Tag-based KASAN reuses a significant part of the generic KASAN code, so
move the common parts to common.c without any functional changes.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/Makefile |   5 +-
 mm/kasan/common.c | 603 ++++++++++++++++++++++++++++++++++++++++++++++
 mm/kasan/kasan.c  | 570 +------------------------------------------
 mm/kasan/kasan.h  |   5 +
 4 files changed, 614 insertions(+), 569 deletions(-)
 create mode 100644 mm/kasan/common.c

diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 3289db38bc87..a6df14bffb6b 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -1,11 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0
 KASAN_SANITIZE := n
+UBSAN_SANITIZE_common.o := n
 UBSAN_SANITIZE_kasan.o := n
 KCOV_INSTRUMENT := n
 
 CFLAGS_REMOVE_kasan.o = -pg
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
+
+CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 CFLAGS_kasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
-obj-y := kasan.o report.o kasan_init.o quarantine.o
+obj-y := common.o kasan.o report.o kasan_init.o quarantine.o
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
new file mode 100644
index 000000000000..5f68c93734ba
--- /dev/null
+++ b/mm/kasan/common.c
@@ -0,0 +1,603 @@
+/*
+ * This file contains common generic and tag-based KASAN code.
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
+ *
+ * Some code borrowed from https://github.com/xairy/kasan-prototype by
+ *        Andrey Konovalov <andreyknvl@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/export.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/kasan.h>
+#include <linux/kernel.h>
+#include <linux/kmemleak.h>
+#include <linux/linkage.h>
+#include <linux/memblock.h>
+#include <linux/memory.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/slab.h>
+#include <linux/stacktrace.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <linux/bug.h>
+
+#include "kasan.h"
+#include "../slab.h"
+
+static inline int in_irqentry_text(unsigned long ptr)
+{
+	return (ptr >= (unsigned long)&__irqentry_text_start &&
+		ptr < (unsigned long)&__irqentry_text_end) ||
+		(ptr >= (unsigned long)&__softirqentry_text_start &&
+		 ptr < (unsigned long)&__softirqentry_text_end);
+}
+
+static inline void filter_irq_stacks(struct stack_trace *trace)
+{
+	int i;
+
+	if (!trace->nr_entries)
+		return;
+	for (i = 0; i < trace->nr_entries; i++)
+		if (in_irqentry_text(trace->entries[i])) {
+			/* Include the irqentry function into the stack. */
+			trace->nr_entries = i + 1;
+			break;
+		}
+}
+
+static inline depot_stack_handle_t save_stack(gfp_t flags)
+{
+	unsigned long entries[KASAN_STACK_DEPTH];
+	struct stack_trace trace = {
+		.nr_entries = 0,
+		.entries = entries,
+		.max_entries = KASAN_STACK_DEPTH,
+		.skip = 0
+	};
+
+	save_stack_trace(&trace);
+	filter_irq_stacks(&trace);
+	if (trace.nr_entries != 0 &&
+	    trace.entries[trace.nr_entries-1] == ULONG_MAX)
+		trace.nr_entries--;
+
+	return depot_save_stack(&trace, flags);
+}
+
+static inline void set_track(struct kasan_track *track, gfp_t flags)
+{
+	track->pid = current->pid;
+	track->stack = save_stack(flags);
+}
+
+void kasan_enable_current(void)
+{
+	current->kasan_depth++;
+}
+
+void kasan_disable_current(void)
+{
+	current->kasan_depth--;
+}
+
+void kasan_check_read(const volatile void *p, unsigned int size)
+{
+	check_memory_region((unsigned long)p, size, false, _RET_IP_);
+}
+EXPORT_SYMBOL(kasan_check_read);
+
+void kasan_check_write(const volatile void *p, unsigned int size)
+{
+	check_memory_region((unsigned long)p, size, true, _RET_IP_);
+}
+EXPORT_SYMBOL(kasan_check_write);
+
+#undef memset
+void *memset(void *addr, int c, size_t len)
+{
+	check_memory_region((unsigned long)addr, len, true, _RET_IP_);
+
+	return __memset(addr, c, len);
+}
+
+#undef memmove
+void *memmove(void *dest, const void *src, size_t len)
+{
+	check_memory_region((unsigned long)src, len, false, _RET_IP_);
+	check_memory_region((unsigned long)dest, len, true, _RET_IP_);
+
+	return __memmove(dest, src, len);
+}
+
+#undef memcpy
+void *memcpy(void *dest, const void *src, size_t len)
+{
+	check_memory_region((unsigned long)src, len, false, _RET_IP_);
+	check_memory_region((unsigned long)dest, len, true, _RET_IP_);
+
+	return __memcpy(dest, src, len);
+}
+
+/*
+ * Poisons the shadow memory for 'size' bytes starting from 'addr'.
+ * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
+ */
+void kasan_poison_shadow(const void *address, size_t size, u8 value)
+{
+	void *shadow_start, *shadow_end;
+
+	shadow_start = kasan_mem_to_shadow(address);
+	shadow_end = kasan_mem_to_shadow(address + size);
+
+	__memset(shadow_start, value, shadow_end - shadow_start);
+}
+
+void kasan_unpoison_shadow(const void *address, size_t size)
+{
+	kasan_poison_shadow(address, size, 0);
+
+	if (size & KASAN_SHADOW_MASK) {
+		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
+		*shadow = size & KASAN_SHADOW_MASK;
+	}
+}
+
+static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
+{
+	void *base = task_stack_page(task);
+	size_t size = sp - base;
+
+	kasan_unpoison_shadow(base, size);
+}
+
+/* Unpoison the entire stack for a task. */
+void kasan_unpoison_task_stack(struct task_struct *task)
+{
+	__kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
+}
+
+/* Unpoison the stack for the current task beyond a watermark sp value. */
+asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
+{
+	/*
+	 * Calculate the task stack base address.  Avoid using 'current'
+	 * because this function is called by early resume code which hasn't
+	 * yet set up the percpu register (%gs).
+	 */
+	void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
+
+	kasan_unpoison_shadow(base, watermark - base);
+}
+
+/*
+ * Clear all poison for the region between the current SP and a provided
+ * watermark value, as is sometimes required prior to hand-crafted asm function
+ * returns in the middle of functions.
+ */
+void kasan_unpoison_stack_above_sp_to(const void *watermark)
+{
+	const void *sp = __builtin_frame_address(0);
+	size_t size = watermark - sp;
+
+	if (WARN_ON(sp > watermark))
+		return;
+	kasan_unpoison_shadow(sp, size);
+}
+
+void kasan_alloc_pages(struct page *page, unsigned int order)
+{
+	if (likely(!PageHighMem(page)))
+		kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
+}
+
+void kasan_free_pages(struct page *page, unsigned int order)
+{
+	if (likely(!PageHighMem(page)))
+		kasan_poison_shadow(page_address(page),
+				PAGE_SIZE << order,
+				KASAN_FREE_PAGE);
+}
+
+/*
+ * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
+ * For larger allocations larger redzones are used.
+ */
+static inline unsigned int optimal_redzone(unsigned int object_size)
+{
+	return
+		object_size <= 64        - 16   ? 16 :
+		object_size <= 128       - 32   ? 32 :
+		object_size <= 512       - 64   ? 64 :
+		object_size <= 4096      - 128  ? 128 :
+		object_size <= (1 << 14) - 256  ? 256 :
+		object_size <= (1 << 15) - 512  ? 512 :
+		object_size <= (1 << 16) - 1024 ? 1024 : 2048;
+}
+
+void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
+			slab_flags_t *flags)
+{
+	unsigned int orig_size = *size;
+	int redzone_adjust;
+
+	/* Add alloc meta. */
+	cache->kasan_info.alloc_meta_offset = *size;
+	*size += sizeof(struct kasan_alloc_meta);
+
+	/* Add free meta. */
+	if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
+	    cache->object_size < sizeof(struct kasan_free_meta)) {
+		cache->kasan_info.free_meta_offset = *size;
+		*size += sizeof(struct kasan_free_meta);
+	}
+	redzone_adjust = optimal_redzone(cache->object_size) -
+		(*size - cache->object_size);
+
+	if (redzone_adjust > 0)
+		*size += redzone_adjust;
+
+	*size = min_t(unsigned int, KMALLOC_MAX_SIZE,
+			max(*size, cache->object_size +
+					optimal_redzone(cache->object_size)));
+
+	/*
+	 * If the metadata doesn't fit, don't enable KASAN at all.
+	 */
+	if (*size <= cache->kasan_info.alloc_meta_offset ||
+			*size <= cache->kasan_info.free_meta_offset) {
+		cache->kasan_info.alloc_meta_offset = 0;
+		cache->kasan_info.free_meta_offset = 0;
+		*size = orig_size;
+		return;
+	}
+
+	*flags |= SLAB_KASAN;
+}
+
+size_t kasan_metadata_size(struct kmem_cache *cache)
+{
+	return (cache->kasan_info.alloc_meta_offset ?
+		sizeof(struct kasan_alloc_meta) : 0) +
+		(cache->kasan_info.free_meta_offset ?
+		sizeof(struct kasan_free_meta) : 0);
+}
+
+struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
+					const void *object)
+{
+	BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
+	return (void *)object + cache->kasan_info.alloc_meta_offset;
+}
+
+struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
+				      const void *object)
+{
+	BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
+	return (void *)object + cache->kasan_info.free_meta_offset;
+}
+
+void kasan_poison_slab(struct page *page)
+{
+	kasan_poison_shadow(page_address(page),
+			PAGE_SIZE << compound_order(page),
+			KASAN_KMALLOC_REDZONE);
+}
+
+void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
+{
+	kasan_unpoison_shadow(object, cache->object_size);
+}
+
+void kasan_poison_object_data(struct kmem_cache *cache, void *object)
+{
+	kasan_poison_shadow(object,
+			round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
+			KASAN_KMALLOC_REDZONE);
+}
+
+void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
+{
+	struct kasan_alloc_meta *alloc_info;
+
+	if (!(cache->flags & SLAB_KASAN))
+		return (void *)object;
+
+	alloc_info = get_alloc_info(cache, object);
+	__memset(alloc_info, 0, sizeof(*alloc_info));
+
+	return (void *)object;
+}
+
+void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
+{
+	return kasan_kmalloc(cache, object, cache->object_size, flags);
+}
+
+static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
+			      unsigned long ip, bool quarantine)
+{
+	s8 shadow_byte;
+	unsigned long rounded_up_size;
+
+	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
+	    object)) {
+		kasan_report_invalid_free(object, ip);
+		return true;
+	}
+
+	/* RCU slabs could be legally used after free within the RCU period */
+	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
+		return false;
+
+	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
+	if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
+		kasan_report_invalid_free(object, ip);
+		return true;
+	}
+
+	rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
+	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
+
+	if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN)))
+		return false;
+
+	set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
+	quarantine_put(get_free_info(cache, object), cache);
+	return true;
+}
+
+bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
+{
+	return __kasan_slab_free(cache, object, ip, true);
+}
+
+void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
+		   gfp_t flags)
+{
+	unsigned long redzone_start;
+	unsigned long redzone_end;
+
+	if (gfpflags_allow_blocking(flags))
+		quarantine_reduce();
+
+	if (unlikely(object == NULL))
+		return NULL;
+
+	redzone_start = round_up((unsigned long)(object + size),
+				KASAN_SHADOW_SCALE_SIZE);
+	redzone_end = round_up((unsigned long)object + cache->object_size,
+				KASAN_SHADOW_SCALE_SIZE);
+
+	kasan_unpoison_shadow(object, size);
+	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
+		KASAN_KMALLOC_REDZONE);
+
+	if (cache->flags & SLAB_KASAN)
+		set_track(&get_alloc_info(cache, object)->alloc_track, flags);
+
+	return (void *)object;
+}
+EXPORT_SYMBOL(kasan_kmalloc);
+
+void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
+{
+	struct page *page;
+	unsigned long redzone_start;
+	unsigned long redzone_end;
+
+	if (gfpflags_allow_blocking(flags))
+		quarantine_reduce();
+
+	if (unlikely(ptr == NULL))
+		return NULL;
+
+	page = virt_to_page(ptr);
+	redzone_start = round_up((unsigned long)(ptr + size),
+				KASAN_SHADOW_SCALE_SIZE);
+	redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
+
+	kasan_unpoison_shadow(ptr, size);
+	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
+		KASAN_PAGE_REDZONE);
+
+	return (void *)ptr;
+}
+
+void *kasan_krealloc(const void *object, size_t size, gfp_t flags)
+{
+	struct page *page;
+
+	if (unlikely(object == ZERO_SIZE_PTR))
+		return (void *)object;
+
+	page = virt_to_head_page(object);
+
+	if (unlikely(!PageSlab(page)))
+		return kasan_kmalloc_large(object, size, flags);
+	else
+		return kasan_kmalloc(page->slab_cache, object, size, flags);
+}
+
+void kasan_poison_kfree(void *ptr, unsigned long ip)
+{
+	struct page *page;
+
+	page = virt_to_head_page(ptr);
+
+	if (unlikely(!PageSlab(page))) {
+		if (ptr != page_address(page)) {
+			kasan_report_invalid_free(ptr, ip);
+			return;
+		}
+		kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
+				KASAN_FREE_PAGE);
+	} else {
+		__kasan_slab_free(page->slab_cache, ptr, ip, false);
+	}
+}
+
+void kasan_kfree_large(void *ptr, unsigned long ip)
+{
+	if (ptr != page_address(virt_to_head_page(ptr)))
+		kasan_report_invalid_free(ptr, ip);
+	/* The object will be poisoned by page_alloc. */
+}
+
+int kasan_module_alloc(void *addr, size_t size)
+{
+	void *ret;
+	size_t scaled_size;
+	size_t shadow_size;
+	unsigned long shadow_start;
+
+	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
+	scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
+	shadow_size = round_up(scaled_size, PAGE_SIZE);
+
+	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
+		return -EINVAL;
+
+	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
+			shadow_start + shadow_size,
+			GFP_KERNEL | __GFP_ZERO,
+			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
+			__builtin_return_address(0));
+
+	if (ret) {
+		find_vm_area(addr)->flags |= VM_KASAN;
+		kmemleak_ignore(ret);
+		return 0;
+	}
+
+	return -ENOMEM;
+}
+
+void kasan_free_shadow(const struct vm_struct *vm)
+{
+	if (vm->flags & VM_KASAN)
+		vfree(kasan_mem_to_shadow(vm->addr));
+}
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static bool shadow_mapped(unsigned long addr)
+{
+	pgd_t *pgd = pgd_offset_k(addr);
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	if (pgd_none(*pgd))
+		return false;
+	p4d = p4d_offset(pgd, addr);
+	if (p4d_none(*p4d))
+		return false;
+	pud = pud_offset(p4d, addr);
+	if (pud_none(*pud))
+		return false;
+
+	/*
+	 * We can't use pud_large() or pud_huge(), the first one is
+	 * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
+	 * pud_bad(), if pud is bad then it's bad because it's huge.
+	 */
+	if (pud_bad(*pud))
+		return true;
+	pmd = pmd_offset(pud, addr);
+	if (pmd_none(*pmd))
+		return false;
+
+	if (pmd_bad(*pmd))
+		return true;
+	pte = pte_offset_kernel(pmd, addr);
+	return !pte_none(*pte);
+}
+
+static int __meminit kasan_mem_notifier(struct notifier_block *nb,
+			unsigned long action, void *data)
+{
+	struct memory_notify *mem_data = data;
+	unsigned long nr_shadow_pages, start_kaddr, shadow_start;
+	unsigned long shadow_end, shadow_size;
+
+	nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
+	start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
+	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
+	shadow_size = nr_shadow_pages << PAGE_SHIFT;
+	shadow_end = shadow_start + shadow_size;
+
+	if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
+		WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
+		return NOTIFY_BAD;
+
+	switch (action) {
+	case MEM_GOING_ONLINE: {
+		void *ret;
+
+		/*
+		 * If shadow is mapped already than it must have been mapped
+		 * during the boot. This could happen if we onlining previously
+		 * offlined memory.
+		 */
+		if (shadow_mapped(shadow_start))
+			return NOTIFY_OK;
+
+		ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
+					shadow_end, GFP_KERNEL,
+					PAGE_KERNEL, VM_NO_GUARD,
+					pfn_to_nid(mem_data->start_pfn),
+					__builtin_return_address(0));
+		if (!ret)
+			return NOTIFY_BAD;
+
+		kmemleak_ignore(ret);
+		return NOTIFY_OK;
+	}
+	case MEM_CANCEL_ONLINE:
+	case MEM_OFFLINE: {
+		struct vm_struct *vm;
+
+		/*
+		 * shadow_start was either mapped during boot by kasan_init()
+		 * or during memory online by __vmalloc_node_range().
+		 * In the latter case we can use vfree() to free shadow.
+		 * Non-NULL result of the find_vm_area() will tell us if
+		 * that was the second case.
+		 *
+		 * Currently it's not possible to free shadow mapped
+		 * during boot by kasan_init(). It's because the code
+		 * to do that hasn't been written yet. So we'll just
+		 * leak the memory.
+		 */
+		vm = find_vm_area((void *)shadow_start);
+		if (vm)
+			vfree((void *)shadow_start);
+	}
+	}
+
+	return NOTIFY_OK;
+}
+
+static int __init kasan_memhotplug_init(void)
+{
+	hotplug_memory_notifier(kasan_mem_notifier, 0);
+
+	return 0;
+}
+
+core_initcall(kasan_memhotplug_init);
+#endif
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 55deff17a4d9..44ec228de0a2 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -1,5 +1,5 @@
 /*
- * This file contains shadow memory manipulation code.
+ * This file contains core KASAN code.
  *
  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
@@ -40,82 +40,6 @@
 #include "kasan.h"
 #include "../slab.h"
 
-void kasan_enable_current(void)
-{
-	current->kasan_depth++;
-}
-
-void kasan_disable_current(void)
-{
-	current->kasan_depth--;
-}
-
-/*
- * Poisons the shadow memory for 'size' bytes starting from 'addr'.
- * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
- */
-static void kasan_poison_shadow(const void *address, size_t size, u8 value)
-{
-	void *shadow_start, *shadow_end;
-
-	shadow_start = kasan_mem_to_shadow(address);
-	shadow_end = kasan_mem_to_shadow(address + size);
-
-	memset(shadow_start, value, shadow_end - shadow_start);
-}
-
-void kasan_unpoison_shadow(const void *address, size_t size)
-{
-	kasan_poison_shadow(address, size, 0);
-
-	if (size & KASAN_SHADOW_MASK) {
-		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
-		*shadow = size & KASAN_SHADOW_MASK;
-	}
-}
-
-static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
-{
-	void *base = task_stack_page(task);
-	size_t size = sp - base;
-
-	kasan_unpoison_shadow(base, size);
-}
-
-/* Unpoison the entire stack for a task. */
-void kasan_unpoison_task_stack(struct task_struct *task)
-{
-	__kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
-}
-
-/* Unpoison the stack for the current task beyond a watermark sp value. */
-asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
-{
-	/*
-	 * Calculate the task stack base address.  Avoid using 'current'
-	 * because this function is called by early resume code which hasn't
-	 * yet set up the percpu register (%gs).
-	 */
-	void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
-
-	kasan_unpoison_shadow(base, watermark - base);
-}
-
-/*
- * Clear all poison for the region between the current SP and a provided
- * watermark value, as is sometimes required prior to hand-crafted asm function
- * returns in the middle of functions.
- */
-void kasan_unpoison_stack_above_sp_to(const void *watermark)
-{
-	const void *sp = __builtin_frame_address(0);
-	size_t size = watermark - sp;
-
-	if (WARN_ON(sp > watermark))
-		return;
-	kasan_unpoison_shadow(sp, size);
-}
-
 /*
  * All functions below always inlined so compiler could
  * perform better optimizations in each of __asan_loadX/__assn_storeX
@@ -260,121 +184,12 @@ static __always_inline void check_memory_region_inline(unsigned long addr,
 	kasan_report(addr, size, write, ret_ip);
 }
 
-static void check_memory_region(unsigned long addr,
-				size_t size, bool write,
+void check_memory_region(unsigned long addr, size_t size, bool write,
 				unsigned long ret_ip)
 {
 	check_memory_region_inline(addr, size, write, ret_ip);
 }
 
-void kasan_check_read(const volatile void *p, unsigned int size)
-{
-	check_memory_region((unsigned long)p, size, false, _RET_IP_);
-}
-EXPORT_SYMBOL(kasan_check_read);
-
-void kasan_check_write(const volatile void *p, unsigned int size)
-{
-	check_memory_region((unsigned long)p, size, true, _RET_IP_);
-}
-EXPORT_SYMBOL(kasan_check_write);
-
-#undef memset
-void *memset(void *addr, int c, size_t len)
-{
-	check_memory_region((unsigned long)addr, len, true, _RET_IP_);
-
-	return __memset(addr, c, len);
-}
-
-#undef memmove
-void *memmove(void *dest, const void *src, size_t len)
-{
-	check_memory_region((unsigned long)src, len, false, _RET_IP_);
-	check_memory_region((unsigned long)dest, len, true, _RET_IP_);
-
-	return __memmove(dest, src, len);
-}
-
-#undef memcpy
-void *memcpy(void *dest, const void *src, size_t len)
-{
-	check_memory_region((unsigned long)src, len, false, _RET_IP_);
-	check_memory_region((unsigned long)dest, len, true, _RET_IP_);
-
-	return __memcpy(dest, src, len);
-}
-
-void kasan_alloc_pages(struct page *page, unsigned int order)
-{
-	if (likely(!PageHighMem(page)))
-		kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
-}
-
-void kasan_free_pages(struct page *page, unsigned int order)
-{
-	if (likely(!PageHighMem(page)))
-		kasan_poison_shadow(page_address(page),
-				PAGE_SIZE << order,
-				KASAN_FREE_PAGE);
-}
-
-/*
- * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
- * For larger allocations larger redzones are used.
- */
-static unsigned int optimal_redzone(unsigned int object_size)
-{
-	return
-		object_size <= 64        - 16   ? 16 :
-		object_size <= 128       - 32   ? 32 :
-		object_size <= 512       - 64   ? 64 :
-		object_size <= 4096      - 128  ? 128 :
-		object_size <= (1 << 14) - 256  ? 256 :
-		object_size <= (1 << 15) - 512  ? 512 :
-		object_size <= (1 << 16) - 1024 ? 1024 : 2048;
-}
-
-void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
-			slab_flags_t *flags)
-{
-	unsigned int orig_size = *size;
-	int redzone_adjust;
-
-	/* Add alloc meta. */
-	cache->kasan_info.alloc_meta_offset = *size;
-	*size += sizeof(struct kasan_alloc_meta);
-
-	/* Add free meta. */
-	if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
-	    cache->object_size < sizeof(struct kasan_free_meta)) {
-		cache->kasan_info.free_meta_offset = *size;
-		*size += sizeof(struct kasan_free_meta);
-	}
-	redzone_adjust = optimal_redzone(cache->object_size) -
-		(*size - cache->object_size);
-
-	if (redzone_adjust > 0)
-		*size += redzone_adjust;
-
-	*size = min_t(unsigned int, KMALLOC_MAX_SIZE,
-			max(*size, cache->object_size +
-					optimal_redzone(cache->object_size)));
-
-	/*
-	 * If the metadata doesn't fit, don't enable KASAN at all.
-	 */
-	if (*size <= cache->kasan_info.alloc_meta_offset ||
-			*size <= cache->kasan_info.free_meta_offset) {
-		cache->kasan_info.alloc_meta_offset = 0;
-		cache->kasan_info.free_meta_offset = 0;
-		*size = orig_size;
-		return;
-	}
-
-	*flags |= SLAB_KASAN;
-}
-
 void kasan_cache_shrink(struct kmem_cache *cache)
 {
 	quarantine_remove_cache(cache);
@@ -386,277 +201,6 @@ void kasan_cache_shutdown(struct kmem_cache *cache)
 		quarantine_remove_cache(cache);
 }
 
-size_t kasan_metadata_size(struct kmem_cache *cache)
-{
-	return (cache->kasan_info.alloc_meta_offset ?
-		sizeof(struct kasan_alloc_meta) : 0) +
-		(cache->kasan_info.free_meta_offset ?
-		sizeof(struct kasan_free_meta) : 0);
-}
-
-void kasan_poison_slab(struct page *page)
-{
-	kasan_poison_shadow(page_address(page),
-			PAGE_SIZE << compound_order(page),
-			KASAN_KMALLOC_REDZONE);
-}
-
-void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
-{
-	kasan_unpoison_shadow(object, cache->object_size);
-}
-
-void kasan_poison_object_data(struct kmem_cache *cache, void *object)
-{
-	kasan_poison_shadow(object,
-			round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
-			KASAN_KMALLOC_REDZONE);
-}
-
-static inline int in_irqentry_text(unsigned long ptr)
-{
-	return (ptr >= (unsigned long)&__irqentry_text_start &&
-		ptr < (unsigned long)&__irqentry_text_end) ||
-		(ptr >= (unsigned long)&__softirqentry_text_start &&
-		 ptr < (unsigned long)&__softirqentry_text_end);
-}
-
-static inline void filter_irq_stacks(struct stack_trace *trace)
-{
-	int i;
-
-	if (!trace->nr_entries)
-		return;
-	for (i = 0; i < trace->nr_entries; i++)
-		if (in_irqentry_text(trace->entries[i])) {
-			/* Include the irqentry function into the stack. */
-			trace->nr_entries = i + 1;
-			break;
-		}
-}
-
-static inline depot_stack_handle_t save_stack(gfp_t flags)
-{
-	unsigned long entries[KASAN_STACK_DEPTH];
-	struct stack_trace trace = {
-		.nr_entries = 0,
-		.entries = entries,
-		.max_entries = KASAN_STACK_DEPTH,
-		.skip = 0
-	};
-
-	save_stack_trace(&trace);
-	filter_irq_stacks(&trace);
-	if (trace.nr_entries != 0 &&
-	    trace.entries[trace.nr_entries-1] == ULONG_MAX)
-		trace.nr_entries--;
-
-	return depot_save_stack(&trace, flags);
-}
-
-static inline void set_track(struct kasan_track *track, gfp_t flags)
-{
-	track->pid = current->pid;
-	track->stack = save_stack(flags);
-}
-
-struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
-					const void *object)
-{
-	BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
-	return (void *)object + cache->kasan_info.alloc_meta_offset;
-}
-
-struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
-				      const void *object)
-{
-	BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
-	return (void *)object + cache->kasan_info.free_meta_offset;
-}
-
-void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
-{
-	struct kasan_alloc_meta *alloc_info;
-
-	if (!(cache->flags & SLAB_KASAN))
-		return (void *)object;
-
-	alloc_info = get_alloc_info(cache, object);
-	__memset(alloc_info, 0, sizeof(*alloc_info));
-
-	return (void *)object;
-}
-
-void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
-{
-	return kasan_kmalloc(cache, object, cache->object_size, flags);
-}
-
-static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
-			      unsigned long ip, bool quarantine)
-{
-	s8 shadow_byte;
-	unsigned long rounded_up_size;
-
-	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
-	    object)) {
-		kasan_report_invalid_free(object, ip);
-		return true;
-	}
-
-	/* RCU slabs could be legally used after free within the RCU period */
-	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
-		return false;
-
-	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
-	if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
-		kasan_report_invalid_free(object, ip);
-		return true;
-	}
-
-	rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
-	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
-
-	if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN)))
-		return false;
-
-	set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
-	quarantine_put(get_free_info(cache, object), cache);
-	return true;
-}
-
-bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
-{
-	return __kasan_slab_free(cache, object, ip, true);
-}
-
-void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
-		   gfp_t flags)
-{
-	unsigned long redzone_start;
-	unsigned long redzone_end;
-
-	if (gfpflags_allow_blocking(flags))
-		quarantine_reduce();
-
-	if (unlikely(object == NULL))
-		return NULL;
-
-	redzone_start = round_up((unsigned long)(object + size),
-				KASAN_SHADOW_SCALE_SIZE);
-	redzone_end = round_up((unsigned long)object + cache->object_size,
-				KASAN_SHADOW_SCALE_SIZE);
-
-	kasan_unpoison_shadow(object, size);
-	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
-		KASAN_KMALLOC_REDZONE);
-
-	if (cache->flags & SLAB_KASAN)
-		set_track(&get_alloc_info(cache, object)->alloc_track, flags);
-
-	return (void *)object;
-}
-EXPORT_SYMBOL(kasan_kmalloc);
-
-void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
-{
-	struct page *page;
-	unsigned long redzone_start;
-	unsigned long redzone_end;
-
-	if (gfpflags_allow_blocking(flags))
-		quarantine_reduce();
-
-	if (unlikely(ptr == NULL))
-		return NULL;
-
-	page = virt_to_page(ptr);
-	redzone_start = round_up((unsigned long)(ptr + size),
-				KASAN_SHADOW_SCALE_SIZE);
-	redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
-
-	kasan_unpoison_shadow(ptr, size);
-	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
-		KASAN_PAGE_REDZONE);
-
-	return (void *)ptr;
-}
-
-void *kasan_krealloc(const void *object, size_t size, gfp_t flags)
-{
-	struct page *page;
-
-	if (unlikely(object == ZERO_SIZE_PTR))
-		return ZERO_SIZE_PTR;
-
-	page = virt_to_head_page(object);
-
-	if (unlikely(!PageSlab(page)))
-		return kasan_kmalloc_large(object, size, flags);
-	else
-		return kasan_kmalloc(page->slab_cache, object, size, flags);
-}
-
-void kasan_poison_kfree(void *ptr, unsigned long ip)
-{
-	struct page *page;
-
-	page = virt_to_head_page(ptr);
-
-	if (unlikely(!PageSlab(page))) {
-		if (ptr != page_address(page)) {
-			kasan_report_invalid_free(ptr, ip);
-			return;
-		}
-		kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
-				KASAN_FREE_PAGE);
-	} else {
-		__kasan_slab_free(page->slab_cache, ptr, ip, false);
-	}
-}
-
-void kasan_kfree_large(void *ptr, unsigned long ip)
-{
-	if (ptr != page_address(virt_to_head_page(ptr)))
-		kasan_report_invalid_free(ptr, ip);
-	/* The object will be poisoned by page_alloc. */
-}
-
-int kasan_module_alloc(void *addr, size_t size)
-{
-	void *ret;
-	size_t scaled_size;
-	size_t shadow_size;
-	unsigned long shadow_start;
-
-	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
-	scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
-	shadow_size = round_up(scaled_size, PAGE_SIZE);
-
-	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
-		return -EINVAL;
-
-	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
-			shadow_start + shadow_size,
-			GFP_KERNEL | __GFP_ZERO,
-			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
-			__builtin_return_address(0));
-
-	if (ret) {
-		find_vm_area(addr)->flags |= VM_KASAN;
-		kmemleak_ignore(ret);
-		return 0;
-	}
-
-	return -ENOMEM;
-}
-
-void kasan_free_shadow(const struct vm_struct *vm)
-{
-	if (vm->flags & VM_KASAN)
-		vfree(kasan_mem_to_shadow(vm->addr));
-}
-
 static void register_global(struct kasan_global *global)
 {
 	size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
@@ -797,113 +341,3 @@ DEFINE_ASAN_SET_SHADOW(f2);
 DEFINE_ASAN_SET_SHADOW(f3);
 DEFINE_ASAN_SET_SHADOW(f5);
 DEFINE_ASAN_SET_SHADOW(f8);
-
-#ifdef CONFIG_MEMORY_HOTPLUG
-static bool shadow_mapped(unsigned long addr)
-{
-	pgd_t *pgd = pgd_offset_k(addr);
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
-
-	if (pgd_none(*pgd))
-		return false;
-	p4d = p4d_offset(pgd, addr);
-	if (p4d_none(*p4d))
-		return false;
-	pud = pud_offset(p4d, addr);
-	if (pud_none(*pud))
-		return false;
-
-	/*
-	 * We can't use pud_large() or pud_huge(), the first one is
-	 * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
-	 * pud_bad(), if pud is bad then it's bad because it's huge.
-	 */
-	if (pud_bad(*pud))
-		return true;
-	pmd = pmd_offset(pud, addr);
-	if (pmd_none(*pmd))
-		return false;
-
-	if (pmd_bad(*pmd))
-		return true;
-	pte = pte_offset_kernel(pmd, addr);
-	return !pte_none(*pte);
-}
-
-static int __meminit kasan_mem_notifier(struct notifier_block *nb,
-			unsigned long action, void *data)
-{
-	struct memory_notify *mem_data = data;
-	unsigned long nr_shadow_pages, start_kaddr, shadow_start;
-	unsigned long shadow_end, shadow_size;
-
-	nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
-	start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
-	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
-	shadow_size = nr_shadow_pages << PAGE_SHIFT;
-	shadow_end = shadow_start + shadow_size;
-
-	if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
-		WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
-		return NOTIFY_BAD;
-
-	switch (action) {
-	case MEM_GOING_ONLINE: {
-		void *ret;
-
-		/*
-		 * If shadow is mapped already than it must have been mapped
-		 * during the boot. This could happen if we onlining previously
-		 * offlined memory.
-		 */
-		if (shadow_mapped(shadow_start))
-			return NOTIFY_OK;
-
-		ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
-					shadow_end, GFP_KERNEL,
-					PAGE_KERNEL, VM_NO_GUARD,
-					pfn_to_nid(mem_data->start_pfn),
-					__builtin_return_address(0));
-		if (!ret)
-			return NOTIFY_BAD;
-
-		kmemleak_ignore(ret);
-		return NOTIFY_OK;
-	}
-	case MEM_CANCEL_ONLINE:
-	case MEM_OFFLINE: {
-		struct vm_struct *vm;
-
-		/*
-		 * shadow_start was either mapped during boot by kasan_init()
-		 * or during memory online by __vmalloc_node_range().
-		 * In the latter case we can use vfree() to free shadow.
-		 * Non-NULL result of the find_vm_area() will tell us if
-		 * that was the second case.
-		 *
-		 * Currently it's not possible to free shadow mapped
-		 * during boot by kasan_init(). It's because the code
-		 * to do that hasn't been written yet. So we'll just
-		 * leak the memory.
-		 */
-		vm = find_vm_area((void *)shadow_start);
-		if (vm)
-			vfree((void *)shadow_start);
-	}
-	}
-
-	return NOTIFY_OK;
-}
-
-static int __init kasan_memhotplug_init(void)
-{
-	hotplug_memory_notifier(kasan_mem_notifier, 0);
-
-	return 0;
-}
-
-core_initcall(kasan_memhotplug_init);
-#endif
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index c12dcfde2ebd..659463800f10 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -105,6 +105,11 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 		<< KASAN_SHADOW_SCALE_SHIFT);
 }
 
+void kasan_poison_shadow(const void *address, size_t size, u8 value);
+
+void check_memory_region(unsigned long addr, size_t size, bool write,
+				unsigned long ret_ip);
+
 void kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 void kasan_report_invalid_free(void *object, unsigned long ip);
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 04/25] kasan: rename source files to reflect the new naming scheme

[Andrey Konovalov]

We now have two KASAN modes: generic KASAN and tag-based KASAN. Rename
kasan.c to generic.c to reflect that. Also rename kasan_init.c to init.c
as it contains initialization code for both KASAN modes.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/Makefile                 | 8 ++++----
 mm/kasan/{kasan.c => generic.c}   | 0
 mm/kasan/{kasan_init.c => init.c} | 0
 3 files changed, 4 insertions(+), 4 deletions(-)
 rename mm/kasan/{kasan.c => generic.c} (100%)
 rename mm/kasan/{kasan_init.c => init.c} (100%)

diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index a6df14bffb6b..d643530b24aa 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -1,14 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0
 KASAN_SANITIZE := n
 UBSAN_SANITIZE_common.o := n
-UBSAN_SANITIZE_kasan.o := n
+UBSAN_SANITIZE_generic.o := n
 KCOV_INSTRUMENT := n
 
-CFLAGS_REMOVE_kasan.o = -pg
+CFLAGS_REMOVE_generic.o = -pg
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
 
 CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_kasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
-obj-y := common.o kasan.o report.o kasan_init.o quarantine.o
+obj-y := common.o generic.o report.o init.o quarantine.o
diff --git a/mm/kasan/kasan.c b/mm/kasan/generic.c
similarity index 100%
rename from mm/kasan/kasan.c
rename to mm/kasan/generic.c
diff --git a/mm/kasan/kasan_init.c b/mm/kasan/init.c
similarity index 100%
rename from mm/kasan/kasan_init.c
rename to mm/kasan/init.c
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 05/25] kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

[Andrey Konovalov]

This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
   that exists now);
2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.

The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
another hardware tag-based KASAN mode, that will rely on hardware memory
tagging support in arm64.

With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
instrument kernel files with -fsantize=kernel-hwaddress (except the ones
for which KASAN_SANITIZE := n is set).

Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.

This commit also adds empty placeholder (for now) implementation of
tag-based KASAN specific hooks inserted by the compiler and adjusts
common hooks implementation.

While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option
is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will
enable once all the infrastracture code has been added.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/compiler-clang.h      |  6 +-
 include/linux/compiler-gcc.h        |  6 ++
 include/linux/compiler_attributes.h | 13 ----
 include/linux/kasan.h               | 16 +++--
 lib/Kconfig.kasan                   | 98 ++++++++++++++++++++++-------
 mm/kasan/Makefile                   |  6 +-
 mm/kasan/generic.c                  |  2 +-
 mm/kasan/kasan.h                    |  3 +-
 mm/kasan/tags.c                     | 75 ++++++++++++++++++++++
 mm/slub.c                           |  2 +-
 scripts/Makefile.kasan              | 53 +++++++++-------
 11 files changed, 214 insertions(+), 66 deletions(-)
 create mode 100644 mm/kasan/tags.c

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 3e7dafb3ea80..39f668d5066b 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -16,9 +16,13 @@
 /* all clang versions usable with the kernel support KASAN ABI version 5 */
 #define KASAN_ABI_VERSION 5
 
+#if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
 /* emulate gcc's __SANITIZE_ADDRESS__ flag */
-#if __has_feature(address_sanitizer)
 #define __SANITIZE_ADDRESS__
+#define __no_sanitize_address \
+		__attribute__((no_sanitize("address", "hwaddress")))
+#else
+#define __no_sanitize_address
 #endif
 
 /*
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 2010493e1040..5776da43da97 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -143,6 +143,12 @@
 #define KASAN_ABI_VERSION 3
 #endif
 
+#if __has_attribute(__no_sanitize_address__)
+#define __no_sanitize_address __attribute__((no_sanitize_address))
+#else
+#define __no_sanitize_address
+#endif
+
 #if GCC_VERSION >= 50100
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index f8c400ba1929..7bceb9469197 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -206,19 +206,6 @@
  */
 #define __noreturn                      __attribute__((__noreturn__))
 
-/*
- * Optional: only supported since gcc >= 4.8
- * Optional: not supported by icc
- *
- *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
- * clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
- */
-#if __has_attribute(__no_sanitize_address__)
-# define __no_sanitize_address          __attribute__((__no_sanitize_address__))
-#else
-# define __no_sanitize_address
-#endif
-
 /*
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
  * clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 52c86a568a4e..b66fdf5ea7ab 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -45,8 +45,6 @@ void kasan_free_pages(struct page *page, unsigned int order);
 
 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 			slab_flags_t *flags);
-void kasan_cache_shrink(struct kmem_cache *cache);
-void kasan_cache_shutdown(struct kmem_cache *cache);
 
 void kasan_poison_slab(struct page *page);
 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
@@ -97,8 +95,6 @@ static inline void kasan_free_pages(struct page *page, unsigned int order) {}
 static inline void kasan_cache_create(struct kmem_cache *cache,
 				      unsigned int *size,
 				      slab_flags_t *flags) {}
-static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
-static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 
 static inline void kasan_poison_slab(struct page *page) {}
 static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
@@ -155,4 +151,16 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
 
 #endif /* CONFIG_KASAN */
 
+#ifdef CONFIG_KASAN_GENERIC
+
+void kasan_cache_shrink(struct kmem_cache *cache);
+void kasan_cache_shutdown(struct kmem_cache *cache);
+
+#else /* CONFIG_KASAN_GENERIC */
+
+static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
+static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
+
+#endif /* CONFIG_KASAN_GENERIC */
+
 #endif /* LINUX_KASAN_H */
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index d0bad1bd9a2b..d8c474b6691e 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -1,36 +1,92 @@
+# This config refers to the generic KASAN mode.
 config HAVE_ARCH_KASAN
 	bool
 
-if HAVE_ARCH_KASAN
+config HAVE_ARCH_KASAN_SW_TAGS
+	bool
+
+config CC_HAS_KASAN_GENERIC
+	def_bool $(cc-option, -fsanitize=kernel-address)
+
+config CC_HAS_KASAN_SW_TAGS
+	def_bool $(cc-option, -fsanitize=kernel-hwaddress)
 
 config KASAN
-	bool "KASan: runtime memory debugger"
+	bool "KASAN: runtime memory debugger"
+	depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
+		   (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
+	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
+	help
+	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
+	  designed to find out-of-bounds accesses and use-after-free bugs.
+	  See Documentation/dev-tools/kasan.rst for details.
+
+choice
+	prompt "KASAN mode"
+	depends on KASAN
+	default KASAN_GENERIC
+	help
+	  KASAN has two modes: generic KASAN (similar to userspace ASan,
+	  x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and
+	  software tag-based KASAN (a version based on software memory
+	  tagging, arm64 only, similar to userspace HWASan, enabled with
+	  CONFIG_KASAN_SW_TAGS).
+	  Both generic and tag-based KASAN are strictly debugging features.
+
+config KASAN_GENERIC
+	bool "Generic mode"
+	depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
 	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
 	select SLUB_DEBUG if SLUB
 	select CONSTRUCTORS
 	select STACKDEPOT
 	help
-	  Enables kernel address sanitizer - runtime memory debugger,
-	  designed to find out-of-bounds accesses and use-after-free bugs.
-	  This is strictly a debugging feature and it requires a gcc version
-	  of 4.9.2 or later. Detection of out of bounds accesses to stack or
-	  global variables requires gcc 5.0 or later.
-	  This feature consumes about 1/8 of available memory and brings about
-	  ~x3 performance slowdown.
+	  Enables generic KASAN mode.
+	  Supported in both GCC and Clang. With GCC it requires version 4.9.2
+	  or later for basic support and version 5.0 or later for detection of
+	  out-of-bounds accesses for stack and global variables and for inline
+	  instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires
+	  version 3.7.0 or later and it doesn't support detection of
+	  out-of-bounds accesses for global variables yet.
+	  This mode consumes about 1/8th of available memory at kernel start
+	  and introduces an overhead of ~x1.5 for the rest of the allocations.
+	  The performance slowdown is ~x3.
 	  For better error detection enable CONFIG_STACKTRACE.
-	  Currently CONFIG_KASAN doesn't work with CONFIG_DEBUG_SLAB
+	  Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
 	  (the resulting kernel does not boot).
 
+config KASAN_SW_TAGS
+	bool "Software tag-based mode"
+	depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
+	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
+	select SLUB_DEBUG if SLUB
+	select CONSTRUCTORS
+	select STACKDEPOT
+	help
+	  Enables software tag-based KASAN mode.
+	  This mode requires Top Byte Ignore support by the CPU and therefore
+	  is only supported for arm64.
+	  This mode requires Clang version 7.0.0 or later.
+	  This mode consumes about 1/16th of available memory at kernel start
+	  and introduces an overhead of ~20% for the rest of the allocations.
+	  This mode may potentially introduce problems relating to pointer
+	  casting and comparison, as it embeds tags into the top byte of each
+	  pointer.
+	  For better error detection enable CONFIG_STACKTRACE.
+	  Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
+	  (the resulting kernel does not boot).
+
+endchoice
+
 config KASAN_EXTRA
-	bool "KAsan: extra checks"
-	depends on KASAN && DEBUG_KERNEL && !COMPILE_TEST
+	bool "KASAN: extra checks"
+	depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST
 	help
-	  This enables further checks in the kernel address sanitizer, for now
-	  it only includes the address-use-after-scope check that can lead
-	  to excessive kernel stack usage, frame size warnings and longer
+	  This enables further checks in generic KASAN, for now it only
+	  includes the address-use-after-scope check that can lead to
+	  excessive kernel stack usage, frame size warnings and longer
 	  compile time.
-	  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 has more
-
+	  See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715
 
 choice
 	prompt "Instrumentation type"
@@ -53,7 +109,7 @@ config KASAN_INLINE
 	  memory accesses. This is faster than outline (in some workloads
 	  it gives about x2 boost over outline instrumentation), but
 	  make kernel's .text size much bigger.
-	  This requires a gcc version of 5.0 or later.
+	  For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.
 
 endchoice
 
@@ -67,11 +123,9 @@ config KASAN_S390_4_LEVEL_PAGING
 	  4-level paging instead.
 
 config TEST_KASAN
-	tristate "Module for testing kasan for bug detection"
+	tristate "Module for testing KASAN for bug detection"
 	depends on m && KASAN
 	help
 	  This is a test module doing various nasty things like
 	  out of bounds accesses, use after free. It is useful for testing
-	  kernel debugging features like kernel address sanitizer.
-
-endif
+	  kernel debugging features like KASAN.
diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index d643530b24aa..68ba1822f003 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -2,6 +2,7 @@
 KASAN_SANITIZE := n
 UBSAN_SANITIZE_common.o := n
 UBSAN_SANITIZE_generic.o := n
+UBSAN_SANITIZE_tags.o := n
 KCOV_INSTRUMENT := n
 
 CFLAGS_REMOVE_generic.o = -pg
@@ -10,5 +11,8 @@ CFLAGS_REMOVE_generic.o = -pg
 
 CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
-obj-y := common.o generic.o report.o init.o quarantine.o
+obj-$(CONFIG_KASAN) := common.o init.o report.o
+obj-$(CONFIG_KASAN_GENERIC) += generic.o quarantine.o
+obj-$(CONFIG_KASAN_SW_TAGS) += tags.o
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 44ec228de0a2..b8de6d33c55c 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -1,5 +1,5 @@
 /*
- * This file contains core KASAN code.
+ * This file contains core generic KASAN code.
  *
  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 659463800f10..19b950eaccff 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -114,7 +114,8 @@ void kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 void kasan_report_invalid_free(void *object, unsigned long ip);
 
-#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB)
+#if defined(CONFIG_KASAN_GENERIC) && \
+	(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
 void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
 void quarantine_reduce(void);
 void quarantine_remove_cache(struct kmem_cache *cache);
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
new file mode 100644
index 000000000000..04194923c543
--- /dev/null
+++ b/mm/kasan/tags.c
@@ -0,0 +1,75 @@
+/*
+ * This file contains core tag-based KASAN code.
+ *
+ * Copyright (c) 2018 Google, Inc.
+ * Author: Andrey Konovalov <andreyknvl@google.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#define DISABLE_BRANCH_PROFILING
+
+#include <linux/export.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/kasan.h>
+#include <linux/kernel.h>
+#include <linux/kmemleak.h>
+#include <linux/linkage.h>
+#include <linux/memblock.h>
+#include <linux/memory.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/slab.h>
+#include <linux/stacktrace.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <linux/bug.h>
+
+#include "kasan.h"
+#include "../slab.h"
+
+void check_memory_region(unsigned long addr, size_t size, bool write,
+				unsigned long ret_ip)
+{
+}
+
+#define DEFINE_HWASAN_LOAD_STORE(size)					\
+	void __hwasan_load##size##_noabort(unsigned long addr)		\
+	{								\
+	}								\
+	EXPORT_SYMBOL(__hwasan_load##size##_noabort);			\
+	void __hwasan_store##size##_noabort(unsigned long addr)		\
+	{								\
+	}								\
+	EXPORT_SYMBOL(__hwasan_store##size##_noabort)
+
+DEFINE_HWASAN_LOAD_STORE(1);
+DEFINE_HWASAN_LOAD_STORE(2);
+DEFINE_HWASAN_LOAD_STORE(4);
+DEFINE_HWASAN_LOAD_STORE(8);
+DEFINE_HWASAN_LOAD_STORE(16);
+
+void __hwasan_loadN_noabort(unsigned long addr, unsigned long size)
+{
+}
+EXPORT_SYMBOL(__hwasan_loadN_noabort);
+
+void __hwasan_storeN_noabort(unsigned long addr, unsigned long size)
+{
+}
+EXPORT_SYMBOL(__hwasan_storeN_noabort);
+
+void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size)
+{
+}
+EXPORT_SYMBOL(__hwasan_tag_memory);
diff --git a/mm/slub.c b/mm/slub.c
index 8561a32910dd..e739d46600b9 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2992,7 +2992,7 @@ static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
 		do_slab_free(s, page, head, tail, cnt, addr);
 }
 
-#ifdef CONFIG_KASAN
+#ifdef CONFIG_KASAN_GENERIC
 void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)
 {
 	do_slab_free(cache, virt_to_head_page(x), x, NULL, 1, addr);
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 69552a39951d..25c259df8ffa 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_KASAN
+ifdef CONFIG_KASAN_GENERIC
+
 ifdef CONFIG_KASAN_INLINE
 	call_threshold := 10000
 else
@@ -12,36 +13,44 @@ CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
 
 cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
 
-ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
-   ifneq ($(CONFIG_COMPILE_TEST),y)
-        $(warning Cannot use CONFIG_KASAN: \
-            -fsanitize=kernel-address is not supported by compiler)
-   endif
-else
-   # -fasan-shadow-offset fails without -fsanitize
-   CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
+# -fasan-shadow-offset fails without -fsanitize
+CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
 			-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET), \
 			$(call cc-option, -fsanitize=kernel-address \
 			-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
 
-   ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
-      CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
-   else
-      # Now add all the compiler specific options that are valid standalone
-      CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
-	$(call cc-param,asan-globals=1) \
-	$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
-	$(call cc-param,asan-stack=1) \
-	$(call cc-param,asan-use-after-scope=1) \
-	$(call cc-param,asan-instrument-allocas=1)
-   endif
-
+ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
+	CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
+else
+	# Now add all the compiler specific options that are valid standalone
+	CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
+	 $(call cc-param,asan-globals=1) \
+	 $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
+	 $(call cc-param,asan-stack=1) \
+	 $(call cc-param,asan-use-after-scope=1) \
+	 $(call cc-param,asan-instrument-allocas=1)
 endif
 
 ifdef CONFIG_KASAN_EXTRA
 CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope)
 endif
 
-CFLAGS_KASAN_NOSANITIZE := -fno-builtin
+endif # CONFIG_KASAN_GENERIC
 
+ifdef CONFIG_KASAN_SW_TAGS
+
+ifdef CONFIG_KASAN_INLINE
+    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
+else
+    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
+endif
+
+CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
+		-mllvm -hwasan-instrument-stack=0 \
+		$(instrumentation_flags)
+
+endif # CONFIG_KASAN_SW_TAGS
+
+ifdef CONFIG_KASAN
+CFLAGS_KASAN_NOSANITIZE := -fno-builtin
 endif
-- 
2.20.0.rc1.387.gf8505762e3-goog


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v13 06/25] kasan, arm64: adjust shadow size for tag-based mode

[Andrey Konovalov]

Tag-based KASAN uses 1 shadow byte for 16 bytes of kernel memory, so it
requires 1/16th of the kernel virtual address space for the shadow memory.

This commit sets KASAN_SHADOW_SCALE_SHIFT to 4 when the tag-based KASAN
mode is enabled.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/Makefile             | 11 ++++++++++-
 arch/arm64/include/asm/memory.h |  7 +++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 6cb9fc7e9382..99e7d08c6083 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -91,10 +91,19 @@ else
 TEXT_OFFSET := 0x00080000
 endif
 
+ifeq ($(CONFIG_KASAN_SW_TAGS), y)
+KASAN_SHADOW_SCALE_SHIFT := 4
+else
+KASAN_SHADOW_SCALE_SHIFT := 3
+endif
+
+KBUILD_CFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
+KBUILD_CPPFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
+KBUILD_AFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
+
 # KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
 #				 - (1 << (64 - KASAN_SHADOW_SCALE_SHIFT))
 # in 32-bit arithmetic
-KASAN_SHADOW_SCALE_SHIFT := 3
 KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
 	(0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \
 	+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) \
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b96442960aea..05fbc7ffcd31 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -74,12 +74,11 @@
 #define KERNEL_END        _end
 
 /*
- * KASAN requires 1/8th of the kernel virtual address space for the shadow
- * region. KASAN can bloat the stack significantly, so double the (minimum)
- * stack size when KASAN is in use.
+ * Generic and tag-based KASAN require 1/8th and 1/16th of the kernel virtual
+ * address space for the shadow region respectively. They can bloat the stack
+ * significantly, so double the (minimum) stack size when they are in use.
  */
 #ifdef CONFIG_KASAN
-#define KASAN_SHADOW_SCALE_SHIFT 3
 #define KASAN_SHADOW_SIZE	(UL(1) << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
 #define KASAN_THREAD_SHIFT	1
 #else
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 07/25] kasan: rename kasan_zero_page to kasan_early_shadow_page

[Andrey Konovalov]

With tag based KASAN mode the early shadow value is 0xff and not 0x00,
so this patch renames kasan_zero_(page|pte|pmd|pud|p4d) to
kasan_early_shadow_(page|pte|pmd|pud|p4d) to avoid confusion.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/kasan_init.c     | 43 ++++++++++++---------
 arch/s390/mm/dump_pagetables.c | 17 +++++----
 arch/s390/mm/kasan_init.c      | 33 +++++++++-------
 arch/x86/mm/dump_pagetables.c  | 11 +++---
 arch/x86/mm/kasan_init_64.c    | 55 +++++++++++++-------------
 arch/xtensa/mm/kasan_init.c    | 18 +++++----
 include/linux/kasan.h          | 12 +++---
 mm/kasan/init.c                | 70 +++++++++++++++++++---------------
 8 files changed, 145 insertions(+), 114 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 63527e585aac..4ebc19422931 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -47,8 +47,9 @@ static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
 				      bool early)
 {
 	if (pmd_none(READ_ONCE(*pmdp))) {
-		phys_addr_t pte_phys = early ? __pa_symbol(kasan_zero_pte)
-					     : kasan_alloc_zeroed_page(node);
+		phys_addr_t pte_phys = early ?
+				__pa_symbol(kasan_early_shadow_pte)
+					: kasan_alloc_zeroed_page(node);
 		__pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
 	}
 
@@ -60,8 +61,9 @@ static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
 				      bool early)
 {
 	if (pud_none(READ_ONCE(*pudp))) {
-		phys_addr_t pmd_phys = early ? __pa_symbol(kasan_zero_pmd)
-					     : kasan_alloc_zeroed_page(node);
+		phys_addr_t pmd_phys = early ?
+				__pa_symbol(kasan_early_shadow_pmd)
+					: kasan_alloc_zeroed_page(node);
 		__pud_populate(pudp, pmd_phys, PMD_TYPE_TABLE);
 	}
 
@@ -72,8 +74,9 @@ static pud_t *__init kasan_pud_offset(pgd_t *pgdp, unsigned long addr, int node,
 				      bool early)
 {
 	if (pgd_none(READ_ONCE(*pgdp))) {
-		phys_addr_t pud_phys = early ? __pa_symbol(kasan_zero_pud)
-					     : kasan_alloc_zeroed_page(node);
+		phys_addr_t pud_phys = early ?
+				__pa_symbol(kasan_early_shadow_pud)
+					: kasan_alloc_zeroed_page(node);
 		__pgd_populate(pgdp, pud_phys, PMD_TYPE_TABLE);
 	}
 
@@ -87,8 +90,9 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 	pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
 
 	do {
-		phys_addr_t page_phys = early ? __pa_symbol(kasan_zero_page)
-					      : kasan_alloc_zeroed_page(node);
+		phys_addr_t page_phys = early ?
+				__pa_symbol(kasan_early_shadow_page)
+					: kasan_alloc_zeroed_page(node);
 		next = addr + PAGE_SIZE;
 		set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 	} while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
@@ -205,14 +209,14 @@ void __init kasan_init(void)
 	kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
 			   early_pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 
-	kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
-				   (void *)mod_shadow_start);
-	kasan_populate_zero_shadow((void *)kimg_shadow_end,
-				   kasan_mem_to_shadow((void *)PAGE_OFFSET));
+	kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
+				    (void *)mod_shadow_start);
+	kasan_populate_early_shadow((void *)kimg_shadow_end,
+				    kasan_mem_to_shadow((void *)PAGE_OFFSET));
 
 	if (kimg_shadow_start > mod_shadow_end)
-		kasan_populate_zero_shadow((void *)mod_shadow_end,
-					   (void *)kimg_shadow_start);
+		kasan_populate_early_shadow((void *)mod_shadow_end,
+					    (void *)kimg_shadow_start);
 
 	for_each_memblock(memory, reg) {
 		void *start = (void *)__phys_to_virt(reg->base);
@@ -227,14 +231,15 @@ void __init kasan_init(void)
 	}
 
 	/*
-	 * KAsan may reuse the contents of kasan_zero_pte directly, so we
-	 * should make sure that it maps the zero page read-only.
+	 * KAsan may reuse the contents of kasan_early_shadow_pte directly,
+	 * so we should make sure that it maps the zero page read-only.
 	 */
 	for (i = 0; i < PTRS_PER_PTE; i++)
-		set_pte(&kasan_zero_pte[i],
-			pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
+		set_pte(&kasan_early_shadow_pte[i],
+			pfn_pte(sym_to_pfn(kasan_early_shadow_page),
+				PAGE_KERNEL_RO));
 
-	memset(kasan_zero_page, 0, PAGE_SIZE);
+	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 
 	/* At this point kasan is fully initialized. Enable error messages */
diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c
index 363f6470d742..3b93ba0b5d8d 100644
--- a/arch/s390/mm/dump_pagetables.c
+++ b/arch/s390/mm/dump_pagetables.c
@@ -111,11 +111,12 @@ static void note_page(struct seq_file *m, struct pg_state *st,
 }
 
 #ifdef CONFIG_KASAN
-static void note_kasan_zero_page(struct seq_file *m, struct pg_state *st)
+static void note_kasan_early_shadow_page(struct seq_file *m,
+						struct pg_state *st)
 {
 	unsigned int prot;
 
-	prot = pte_val(*kasan_zero_pte) &
+	prot = pte_val(*kasan_early_shadow_pte) &
 		(_PAGE_PROTECT | _PAGE_INVALID | _PAGE_NOEXEC);
 	note_page(m, st, prot, 4);
 }
@@ -154,8 +155,8 @@ static void walk_pmd_level(struct seq_file *m, struct pg_state *st,
 	int i;
 
 #ifdef CONFIG_KASAN
-	if ((pud_val(*pud) & PAGE_MASK) == __pa(kasan_zero_pmd)) {
-		note_kasan_zero_page(m, st);
+	if ((pud_val(*pud) & PAGE_MASK) == __pa(kasan_early_shadow_pmd)) {
+		note_kasan_early_shadow_page(m, st);
 		return;
 	}
 #endif
@@ -185,8 +186,8 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st,
 	int i;
 
 #ifdef CONFIG_KASAN
-	if ((p4d_val(*p4d) & PAGE_MASK) == __pa(kasan_zero_pud)) {
-		note_kasan_zero_page(m, st);
+	if ((p4d_val(*p4d) & PAGE_MASK) == __pa(kasan_early_shadow_pud)) {
+		note_kasan_early_shadow_page(m, st);
 		return;
 	}
 #endif
@@ -215,8 +216,8 @@ static void walk_p4d_level(struct seq_file *m, struct pg_state *st,
 	int i;
 
 #ifdef CONFIG_KASAN
-	if ((pgd_val(*pgd) & PAGE_MASK) == __pa(kasan_zero_p4d)) {
-		note_kasan_zero_page(m, st);
+	if ((pgd_val(*pgd) & PAGE_MASK) == __pa(kasan_early_shadow_p4d)) {
+		note_kasan_early_shadow_page(m, st);
 		return;
 	}
 #endif
diff --git a/arch/s390/mm/kasan_init.c b/arch/s390/mm/kasan_init.c
index acb9645b762b..bac5c27d11fc 100644
--- a/arch/s390/mm/kasan_init.c
+++ b/arch/s390/mm/kasan_init.c
@@ -107,7 +107,8 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, PGDIR_SIZE) &&
 			    end - address >= PGDIR_SIZE) {
-				pgd_populate(&init_mm, pg_dir, kasan_zero_p4d);
+				pgd_populate(&init_mm, pg_dir,
+						kasan_early_shadow_p4d);
 				address = (address + PGDIR_SIZE) & PGDIR_MASK;
 				continue;
 			}
@@ -120,7 +121,8 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, P4D_SIZE) &&
 			    end - address >= P4D_SIZE) {
-				p4d_populate(&init_mm, p4_dir, kasan_zero_pud);
+				p4d_populate(&init_mm, p4_dir,
+						kasan_early_shadow_pud);
 				address = (address + P4D_SIZE) & P4D_MASK;
 				continue;
 			}
@@ -133,7 +135,8 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, PUD_SIZE) &&
 			    end - address >= PUD_SIZE) {
-				pud_populate(&init_mm, pu_dir, kasan_zero_pmd);
+				pud_populate(&init_mm, pu_dir,
+						kasan_early_shadow_pmd);
 				address = (address + PUD_SIZE) & PUD_MASK;
 				continue;
 			}
@@ -146,7 +149,8 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, PMD_SIZE) &&
 			    end - address >= PMD_SIZE) {
-				pmd_populate(&init_mm, pm_dir, kasan_zero_pte);
+				pmd_populate(&init_mm, pm_dir,
+						kasan_early_shadow_pte);
 				address = (address + PMD_SIZE) & PMD_MASK;
 				continue;
 			}
@@ -188,7 +192,7 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 				pte_val(*pt_dir) = __pa(page) | pgt_prot;
 				break;
 			case POPULATE_ZERO_SHADOW:
-				page = kasan_zero_page;
+				page = kasan_early_shadow_page;
 				pte_val(*pt_dir) = __pa(page) | pgt_prot_zero;
 				break;
 			}
@@ -256,14 +260,14 @@ void __init kasan_early_init(void)
 	unsigned long vmax;
 	unsigned long pgt_prot = pgprot_val(PAGE_KERNEL_RO);
 	pte_t pte_z;
-	pmd_t pmd_z = __pmd(__pa(kasan_zero_pte) | _SEGMENT_ENTRY);
-	pud_t pud_z = __pud(__pa(kasan_zero_pmd) | _REGION3_ENTRY);
-	p4d_t p4d_z = __p4d(__pa(kasan_zero_pud) | _REGION2_ENTRY);
+	pmd_t pmd_z = __pmd(__pa(kasan_early_shadow_pte) | _SEGMENT_ENTRY);
+	pud_t pud_z = __pud(__pa(kasan_early_shadow_pmd) | _REGION3_ENTRY);
+	p4d_t p4d_z = __p4d(__pa(kasan_early_shadow_pud) | _REGION2_ENTRY);
 
 	kasan_early_detect_facilities();
 	if (!has_nx)
 		pgt_prot &= ~_PAGE_NOEXEC;
-	pte_z = __pte(__pa(kasan_zero_page) | pgt_prot);
+	pte_z = __pte(__pa(kasan_early_shadow_page) | pgt_prot);
 
 	memsize = get_mem_detect_end();
 	if (!memsize)
@@ -292,10 +296,13 @@ void __init kasan_early_init(void)
 	}
 
 	/* init kasan zero shadow */
-	crst_table_init((unsigned long *)kasan_zero_p4d, p4d_val(p4d_z));
-	crst_table_init((unsigned long *)kasan_zero_pud, pud_val(pud_z));
-	crst_table_init((unsigned long *)kasan_zero_pmd, pmd_val(pmd_z));
-	memset64((u64 *)kasan_zero_pte, pte_val(pte_z), PTRS_PER_PTE);
+	crst_table_init((unsigned long *)kasan_early_shadow_p4d,
+				p4d_val(p4d_z));
+	crst_table_init((unsigned long *)kasan_early_shadow_pud,
+				pud_val(pud_z));
+	crst_table_init((unsigned long *)kasan_early_shadow_pmd,
+				pmd_val(pmd_z));
+	memset64((u64 *)kasan_early_shadow_pte, pte_val(pte_z), PTRS_PER_PTE);
 
 	shadow_alloc_size = memsize >> KASAN_SHADOW_SCALE_SHIFT;
 	pgalloc_low = round_up((unsigned long)_end, _SEGMENT_SIZE);
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index fc37bbd23eb8..c4696ab9a72b 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -380,7 +380,7 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 
 /*
  * This is an optimization for KASAN=y case. Since all kasan page tables
- * eventually point to the kasan_zero_page we could call note_page()
+ * eventually point to the kasan_early_shadow_page we could call note_page()
  * right away without walking through lower level page tables. This saves
  * us dozens of seconds (minutes for 5-level config) while checking for
  * W+X mapping or reading kernel_page_tables debugfs file.
@@ -388,10 +388,11 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
 static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
 				void *pt)
 {
-	if (__pa(pt) == __pa(kasan_zero_pmd) ||
-	    (pgtable_l5_enabled() && __pa(pt) == __pa(kasan_zero_p4d)) ||
-	    __pa(pt) == __pa(kasan_zero_pud)) {
-		pgprotval_t prot = pte_flags(kasan_zero_pte[0]);
+	if (__pa(pt) == __pa(kasan_early_shadow_pmd) ||
+	    (pgtable_l5_enabled() &&
+			__pa(pt) == __pa(kasan_early_shadow_p4d)) ||
+	    __pa(pt) == __pa(kasan_early_shadow_pud)) {
+		pgprotval_t prot = pte_flags(kasan_early_shadow_pte[0]);
 		note_page(m, st, __pgprot(prot), 0, 5);
 		return true;
 	}
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 04a9cf6b034f..462fde83b515 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -211,7 +211,8 @@ static void __init kasan_early_p4d_populate(pgd_t *pgd,
 	unsigned long next;
 
 	if (pgd_none(*pgd)) {
-		pgd_entry = __pgd(_KERNPG_TABLE | __pa_nodebug(kasan_zero_p4d));
+		pgd_entry = __pgd(_KERNPG_TABLE |
+					__pa_nodebug(kasan_early_shadow_p4d));
 		set_pgd(pgd, pgd_entry);
 	}
 
@@ -222,7 +223,8 @@ static void __init kasan_early_p4d_populate(pgd_t *pgd,
 		if (!p4d_none(*p4d))
 			continue;
 
-		p4d_entry = __p4d(_KERNPG_TABLE | __pa_nodebug(kasan_zero_pud));
+		p4d_entry = __p4d(_KERNPG_TABLE |
+					__pa_nodebug(kasan_early_shadow_pud));
 		set_p4d(p4d, p4d_entry);
 	} while (p4d++, addr = next, addr != end && p4d_none(*p4d));
 }
@@ -261,10 +263,11 @@ static struct notifier_block kasan_die_notifier = {
 void __init kasan_early_init(void)
 {
 	int i;
-	pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL | _PAGE_ENC;
-	pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
-	pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
-	p4dval_t p4d_val = __pa_nodebug(kasan_zero_pud) | _KERNPG_TABLE;
+	pteval_t pte_val = __pa_nodebug(kasan_early_shadow_page) |
+				__PAGE_KERNEL | _PAGE_ENC;
+	pmdval_t pmd_val = __pa_nodebug(kasan_early_shadow_pte) | _KERNPG_TABLE;
+	pudval_t pud_val = __pa_nodebug(kasan_early_shadow_pmd) | _KERNPG_TABLE;
+	p4dval_t p4d_val = __pa_nodebug(kasan_early_shadow_pud) | _KERNPG_TABLE;
 
 	/* Mask out unsupported __PAGE_KERNEL bits: */
 	pte_val &= __default_kernel_pte_mask;
@@ -273,16 +276,16 @@ void __init kasan_early_init(void)
 	p4d_val &= __default_kernel_pte_mask;
 
 	for (i = 0; i < PTRS_PER_PTE; i++)
-		kasan_zero_pte[i] = __pte(pte_val);
+		kasan_early_shadow_pte[i] = __pte(pte_val);
 
 	for (i = 0; i < PTRS_PER_PMD; i++)
-		kasan_zero_pmd[i] = __pmd(pmd_val);
+		kasan_early_shadow_pmd[i] = __pmd(pmd_val);
 
 	for (i = 0; i < PTRS_PER_PUD; i++)
-		kasan_zero_pud[i] = __pud(pud_val);
+		kasan_early_shadow_pud[i] = __pud(pud_val);
 
 	for (i = 0; pgtable_l5_enabled() && i < PTRS_PER_P4D; i++)
-		kasan_zero_p4d[i] = __p4d(p4d_val);
+		kasan_early_shadow_p4d[i] = __p4d(p4d_val);
 
 	kasan_map_early_shadow(early_top_pgt);
 	kasan_map_early_shadow(init_top_pgt);
@@ -326,7 +329,7 @@ void __init kasan_init(void)
 
 	clear_pgds(KASAN_SHADOW_START & PGDIR_MASK, KASAN_SHADOW_END);
 
-	kasan_populate_zero_shadow((void *)(KASAN_SHADOW_START & PGDIR_MASK),
+	kasan_populate_early_shadow((void *)(KASAN_SHADOW_START & PGDIR_MASK),
 			kasan_mem_to_shadow((void *)PAGE_OFFSET));
 
 	for (i = 0; i < E820_MAX_ENTRIES; i++) {
@@ -338,41 +341,41 @@ void __init kasan_init(void)
 
 	shadow_cpu_entry_begin = (void *)CPU_ENTRY_AREA_BASE;
 	shadow_cpu_entry_begin = kasan_mem_to_shadow(shadow_cpu_entry_begin);
-	shadow_cpu_entry_begin = (void *)round_down((unsigned long)shadow_cpu_entry_begin,
-						PAGE_SIZE);
+	shadow_cpu_entry_begin = (void *)round_down(
+			(unsigned long)shadow_cpu_entry_begin, PAGE_SIZE);
 
 	shadow_cpu_entry_end = (void *)(CPU_ENTRY_AREA_BASE +
 					CPU_ENTRY_AREA_MAP_SIZE);
 	shadow_cpu_entry_end = kasan_mem_to_shadow(shadow_cpu_entry_end);
-	shadow_cpu_entry_end = (void *)round_up((unsigned long)shadow_cpu_entry_end,
-					PAGE_SIZE);
+	shadow_cpu_entry_end = (void *)round_up(
+			(unsigned long)shadow_cpu_entry_end, PAGE_SIZE);
 
-	kasan_populate_zero_shadow(
+	kasan_populate_early_shadow(
 		kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 		shadow_cpu_entry_begin);
 
 	kasan_populate_shadow((unsigned long)shadow_cpu_entry_begin,
 			      (unsigned long)shadow_cpu_entry_end, 0);
 
-	kasan_populate_zero_shadow(shadow_cpu_entry_end,
-				kasan_mem_to_shadow((void *)__START_KERNEL_map));
+	kasan_populate_early_shadow(shadow_cpu_entry_end,
+			kasan_mem_to_shadow((void *)__START_KERNEL_map));
 
 	kasan_populate_shadow((unsigned long)kasan_mem_to_shadow(_stext),
 			      (unsigned long)kasan_mem_to_shadow(_end),
 			      early_pfn_to_nid(__pa(_stext)));
 
-	kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
-				(void *)KASAN_SHADOW_END);
+	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)MODULES_END),
+					(void *)KASAN_SHADOW_END);
 
 	load_cr3(init_top_pgt);
 	__flush_tlb_all();
 
 	/*
-	 * kasan_zero_page has been used as early shadow memory, thus it may
-	 * contain some garbage. Now we can clear and write protect it, since
-	 * after the TLB flush no one should write to it.
+	 * kasan_early_shadow_page has been used as early shadow memory, thus
+	 * it may contain some garbage. Now we can clear and write protect it,
+	 * since after the TLB flush no one should write to it.
 	 */
-	memset(kasan_zero_page, 0, PAGE_SIZE);
+	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 	for (i = 0; i < PTRS_PER_PTE; i++) {
 		pte_t pte;
 		pgprot_t prot;
@@ -380,8 +383,8 @@ void __init kasan_init(void)
 		prot = __pgprot(__PAGE_KERNEL_RO | _PAGE_ENC);
 		pgprot_val(prot) &= __default_kernel_pte_mask;
 
-		pte = __pte(__pa(kasan_zero_page) | pgprot_val(prot));
-		set_pte(&kasan_zero_pte[i], pte);
+		pte = __pte(__pa(kasan_early_shadow_page) | pgprot_val(prot));
+		set_pte(&kasan_early_shadow_pte[i], pte);
 	}
 	/* Flush TLBs again to be sure that write protection applied. */
 	__flush_tlb_all();
diff --git a/arch/xtensa/mm/kasan_init.c b/arch/xtensa/mm/kasan_init.c
index 6b95ca43aec0..1734cda6bc4a 100644
--- a/arch/xtensa/mm/kasan_init.c
+++ b/arch/xtensa/mm/kasan_init.c
@@ -24,12 +24,13 @@ void __init kasan_early_init(void)
 	int i;
 
 	for (i = 0; i < PTRS_PER_PTE; ++i)
-		set_pte(kasan_zero_pte + i,
-			mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL));
+		set_pte(kasan_early_shadow_pte + i,
+			mk_pte(virt_to_page(kasan_early_shadow_page),
+				PAGE_KERNEL));
 
 	for (vaddr = 0; vaddr < KASAN_SHADOW_SIZE; vaddr += PMD_SIZE, ++pmd) {
 		BUG_ON(!pmd_none(*pmd));
-		set_pmd(pmd, __pmd((unsigned long)kasan_zero_pte));
+		set_pmd(pmd, __pmd((unsigned long)kasan_early_shadow_pte));
 	}
 	early_trap_init();
 }
@@ -80,13 +81,16 @@ void __init kasan_init(void)
 	populate(kasan_mem_to_shadow((void *)VMALLOC_START),
 		 kasan_mem_to_shadow((void *)XCHAL_KSEG_BYPASS_VADDR));
 
-	/* Write protect kasan_zero_page and zero-initialize it again. */
+	/*
+	 * Write protect kasan_early_shadow_page and zero-initialize it again.
+	 */
 	for (i = 0; i < PTRS_PER_PTE; ++i)
-		set_pte(kasan_zero_pte + i,
-			mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL_RO));
+		set_pte(kasan_early_shadow_pte + i,
+			mk_pte(virt_to_page(kasan_early_shadow_page),
+				PAGE_KERNEL_RO));
 
 	local_flush_tlb_all();
-	memset(kasan_zero_page, 0, PAGE_SIZE);
+	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
 
 	/* At this point kasan is fully initialized. Enable error messages. */
 	current->kasan_depth = 0;
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index b66fdf5ea7ab..ec22d548d0d7 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -14,13 +14,13 @@ struct task_struct;
 #include <asm/kasan.h>
 #include <asm/pgtable.h>
 
-extern unsigned char kasan_zero_page[PAGE_SIZE];
-extern pte_t kasan_zero_pte[PTRS_PER_PTE];
-extern pmd_t kasan_zero_pmd[PTRS_PER_PMD];
-extern pud_t kasan_zero_pud[PTRS_PER_PUD];
-extern p4d_t kasan_zero_p4d[MAX_PTRS_PER_P4D];
+extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
+extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
+extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
+extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
+extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
 
-int kasan_populate_zero_shadow(const void *shadow_start,
+int kasan_populate_early_shadow(const void *shadow_start,
 				const void *shadow_end);
 
 static inline void *kasan_mem_to_shadow(const void *addr)
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index c7550eb65922..2b21d3717d62 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -30,13 +30,13 @@
  *   - Latter it reused it as zero shadow to cover large ranges of memory
  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
  */
-unsigned char kasan_zero_page[PAGE_SIZE] __page_aligned_bss;
+unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
 
 #if CONFIG_PGTABLE_LEVELS > 4
-p4d_t kasan_zero_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
+p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
 static inline bool kasan_p4d_table(pgd_t pgd)
 {
-	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_zero_p4d));
+	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
 }
 #else
 static inline bool kasan_p4d_table(pgd_t pgd)
@@ -45,10 +45,10 @@ static inline bool kasan_p4d_table(pgd_t pgd)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 3
-pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
+pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
 static inline bool kasan_pud_table(p4d_t p4d)
 {
-	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_zero_pud));
+	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
 }
 #else
 static inline bool kasan_pud_table(p4d_t p4d)
@@ -57,10 +57,10 @@ static inline bool kasan_pud_table(p4d_t p4d)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 2
-pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss;
+pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
 static inline bool kasan_pmd_table(pud_t pud)
 {
-	return pud_page(pud) == virt_to_page(lm_alias(kasan_zero_pmd));
+	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
 }
 #else
 static inline bool kasan_pmd_table(pud_t pud)
@@ -68,16 +68,16 @@ static inline bool kasan_pmd_table(pud_t pud)
 	return 0;
 }
 #endif
-pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss;
+pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
 
 static inline bool kasan_pte_table(pmd_t pmd)
 {
-	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_zero_pte));
+	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
 }
 
-static inline bool kasan_zero_page_entry(pte_t pte)
+static inline bool kasan_early_shadow_page_entry(pte_t pte)
 {
-	return pte_page(pte) == virt_to_page(lm_alias(kasan_zero_page));
+	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
 }
 
 static __init void *early_alloc(size_t size, int node)
@@ -92,7 +92,8 @@ static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
 	pte_t *pte = pte_offset_kernel(pmd, addr);
 	pte_t zero_pte;
 
-	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_zero_page)), PAGE_KERNEL);
+	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
+				PAGE_KERNEL);
 	zero_pte = pte_wrprotect(zero_pte);
 
 	while (addr + PAGE_SIZE <= end) {
@@ -112,7 +113,8 @@ static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 		next = pmd_addr_end(addr, end);
 
 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
-			pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
+			pmd_populate_kernel(&init_mm, pmd,
+					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}
 
@@ -145,9 +147,11 @@ static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
 			pmd_t *pmd;
 
-			pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
+			pud_populate(&init_mm, pud,
+					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
-			pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
+			pmd_populate_kernel(&init_mm, pmd,
+					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}
 
@@ -181,12 +185,14 @@ static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 			pud_t *pud;
 			pmd_t *pmd;
 
-			p4d_populate(&init_mm, p4d, lm_alias(kasan_zero_pud));
+			p4d_populate(&init_mm, p4d,
+					lm_alias(kasan_early_shadow_pud));
 			pud = pud_offset(p4d, addr);
-			pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
+			pud_populate(&init_mm, pud,
+					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
 			pmd_populate_kernel(&init_mm, pmd,
-						lm_alias(kasan_zero_pte));
+					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}
 
@@ -209,13 +215,13 @@ static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
 }
 
 /**
- * kasan_populate_zero_shadow - populate shadow memory region with
- *                               kasan_zero_page
+ * kasan_populate_early_shadow - populate shadow memory region with
+ *                               kasan_early_shadow_page
  * @shadow_start - start of the memory range to populate
  * @shadow_end   - end of the memory range to populate
  */
-int __ref kasan_populate_zero_shadow(const void *shadow_start,
-				const void *shadow_end)
+int __ref kasan_populate_early_shadow(const void *shadow_start,
+					const void *shadow_end)
 {
 	unsigned long addr = (unsigned long)shadow_start;
 	unsigned long end = (unsigned long)shadow_end;
@@ -231,7 +237,7 @@ int __ref kasan_populate_zero_shadow(const void *shadow_start,
 			pmd_t *pmd;
 
 			/*
-			 * kasan_zero_pud should be populated with pmds
+			 * kasan_early_shadow_pud should be populated with pmds
 			 * at this moment.
 			 * [pud,pmd]_populate*() below needed only for
 			 * 3,2 - level page tables where we don't have
@@ -241,21 +247,25 @@ int __ref kasan_populate_zero_shadow(const void *shadow_start,
 			 * The ifndef is required to avoid build breakage.
 			 *
 			 * With 5level-fixup.h, pgd_populate() is not nop and
-			 * we reference kasan_zero_p4d. It's not defined
+			 * we reference kasan_early_shadow_p4d. It's not defined
 			 * unless 5-level paging enabled.
 			 *
 			 * The ifndef can be dropped once all KASAN-enabled
 			 * architectures will switch to pgtable-nop4d.h.
 			 */
 #ifndef __ARCH_HAS_5LEVEL_HACK
-			pgd_populate(&init_mm, pgd, lm_alias(kasan_zero_p4d));
+			pgd_populate(&init_mm, pgd,
+					lm_alias(kasan_early_shadow_p4d));
 #endif
 			p4d = p4d_offset(pgd, addr);
-			p4d_populate(&init_mm, p4d, lm_alias(kasan_zero_pud));
+			p4d_populate(&init_mm, p4d,
+					lm_alias(kasan_early_shadow_pud));
 			pud = pud_offset(p4d, addr);
-			pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
+			pud_populate(&init_mm, pud,
+					lm_alias(kasan_early_shadow_pmd));
 			pmd = pmd_offset(pud, addr);
-			pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
+			pmd_populate_kernel(&init_mm, pmd,
+					lm_alias(kasan_early_shadow_pte));
 			continue;
 		}
 
@@ -350,7 +360,7 @@ static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
 		if (!pte_present(*pte))
 			continue;
 
-		if (WARN_ON(!kasan_zero_page_entry(*pte)))
+		if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
 			continue;
 		pte_clear(&init_mm, addr, pte);
 	}
@@ -480,7 +490,7 @@ int kasan_add_zero_shadow(void *start, unsigned long size)
 	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
 		return -EINVAL;
 
-	ret = kasan_populate_zero_shadow(shadow_start, shadow_end);
+	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
 	if (ret)
 		kasan_remove_zero_shadow(shadow_start,
 					size >> KASAN_SHADOW_SCALE_SHIFT);
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 08/25] kasan: initialize shadow to 0xff for tag-based mode

[Andrey Konovalov]

A tag-based KASAN shadow memory cell contains a memory tag, that
corresponds to the tag in the top byte of the pointer, that points to that
memory. The native top byte value of kernel pointers is 0xff, so with
tag-based KASAN we need to initialize shadow memory to 0xff.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/kasan_init.c | 15 +++++++++++++--
 include/linux/kasan.h      |  8 ++++++++
 mm/kasan/common.c          |  3 ++-
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 4ebc19422931..7a4a0904cac8 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -43,6 +43,15 @@ static phys_addr_t __init kasan_alloc_zeroed_page(int node)
 	return __pa(p);
 }
 
+static phys_addr_t __init kasan_alloc_raw_page(int node)
+{
+	void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
+						__pa(MAX_DMA_ADDRESS),
+						MEMBLOCK_ALLOC_ACCESSIBLE,
+						node);
+	return __pa(p);
+}
+
 static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
 				      bool early)
 {
@@ -92,7 +101,9 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 	do {
 		phys_addr_t page_phys = early ?
 				__pa_symbol(kasan_early_shadow_page)
-					: kasan_alloc_zeroed_page(node);
+					: kasan_alloc_raw_page(node);
+		if (!early)
+			memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
 		next = addr + PAGE_SIZE;
 		set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 	} while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
@@ -239,7 +250,7 @@ void __init kasan_init(void)
 			pfn_pte(sym_to_pfn(kasan_early_shadow_page),
 				PAGE_KERNEL_RO));
 
-	memset(kasan_early_shadow_page, 0, PAGE_SIZE);
+	memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 
 	/* At this point kasan is fully initialized. Enable error messages */
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index ec22d548d0d7..c56af24bd3e7 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -153,6 +153,8 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
 
 #ifdef CONFIG_KASAN_GENERIC
 
+#define KASAN_SHADOW_INIT 0
+
 void kasan_cache_shrink(struct kmem_cache *cache);
 void kasan_cache_shutdown(struct kmem_cache *cache);
 
@@ -163,4 +165,10 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 
 #endif /* CONFIG_KASAN_GENERIC */
 
+#ifdef CONFIG_KASAN_SW_TAGS
+
+#define KASAN_SHADOW_INIT 0xFF
+
+#endif /* CONFIG_KASAN_SW_TAGS */
+
 #endif /* LINUX_KASAN_H */
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 5f68c93734ba..7134e75447ff 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -473,11 +473,12 @@ int kasan_module_alloc(void *addr, size_t size)
 
 	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 			shadow_start + shadow_size,
-			GFP_KERNEL | __GFP_ZERO,
+			GFP_KERNEL,
 			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 			__builtin_return_address(0));
 
 	if (ret) {
+		__memset(ret, KASAN_SHADOW_INIT, shadow_size);
 		find_vm_area(addr)->flags |= VM_KASAN;
 		kmemleak_ignore(ret);
 		return 0;
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 09/25] arm64: move untagged_addr macro from uaccess.h to memory.h

[Andrey Konovalov]

Move the untagged_addr() macro from arch/arm64/include/asm/uaccess.h
to arch/arm64/include/asm/memory.h to be later reused by KASAN.

Also make the untagged_addr() macro accept all kinds of address types
(void *, unsigned long, etc.). This allows not to specify type casts in
each place where the macro is used. This is done by using __typeof__.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/memory.h  | 8 ++++++++
 arch/arm64/include/asm/uaccess.h | 7 -------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 05fbc7ffcd31..e2c9857157f2 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -211,6 +211,14 @@ static inline unsigned long kaslr_offset(void)
  */
 #define PHYS_PFN_OFFSET	(PHYS_OFFSET >> PAGE_SHIFT)
 
+/*
+ * When dealing with data aborts, watchpoints, or instruction traps we may end
+ * up with a tagged userland pointer. Clear the tag to get a sane pointer to
+ * pass on to access_ok(), for instance.
+ */
+#define untagged_addr(addr)	\
+	((__typeof__(addr))sign_extend64((u64)(addr), 55))
+
 /*
  * Physical vs virtual RAM address space conversion.  These are
  * private definitions which should NOT be used outside memory.h
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 07c34087bd5e..281a1e47263d 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -96,13 +96,6 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
 	return ret;
 }
 
-/*
- * When dealing with data aborts, watchpoints, or instruction traps we may end
- * up with a tagged userland pointer. Clear the tag to get a sane pointer to
- * pass on to access_ok(), for instance.
- */
-#define untagged_addr(addr)		sign_extend64(addr, 55)
-
 #define access_ok(type, addr, size)	__range_ok(addr, size)
 #define user_addr_max			get_fs
 
-- 
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[PATCH v13 10/25] kasan: add tag related helper functions

[Andrey Konovalov]

This commit adds a few helper functions, that are meant to be used to
work with tags embedded in the top byte of kernel pointers: to set, to
get or to reset the top byte.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/kasan.h  |  8 +++++--
 arch/arm64/include/asm/memory.h | 12 +++++++++++
 arch/arm64/mm/kasan_init.c      |  2 ++
 include/linux/kasan.h           | 13 ++++++++++++
 mm/kasan/kasan.h                | 31 +++++++++++++++++++++++++++
 mm/kasan/tags.c                 | 37 +++++++++++++++++++++++++++++++++
 6 files changed, 101 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h
index 8758bb008436..b52aacd2c526 100644
--- a/arch/arm64/include/asm/kasan.h
+++ b/arch/arm64/include/asm/kasan.h
@@ -4,12 +4,16 @@
 
 #ifndef __ASSEMBLY__
 
-#ifdef CONFIG_KASAN
-
 #include <linux/linkage.h>
 #include <asm/memory.h>
 #include <asm/pgtable-types.h>
 
+#define arch_kasan_set_tag(addr, tag)	__tag_set(addr, tag)
+#define arch_kasan_reset_tag(addr)	__tag_reset(addr)
+#define arch_kasan_get_tag(addr)	__tag_get(addr)
+
+#ifdef CONFIG_KASAN
+
 /*
  * KASAN_SHADOW_START: beginning of the kernel virtual addresses.
  * KASAN_SHADOW_END: KASAN_SHADOW_START + 1/N of kernel virtual addresses,
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index e2c9857157f2..83c1366a1233 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -219,6 +219,18 @@ static inline unsigned long kaslr_offset(void)
 #define untagged_addr(addr)	\
 	((__typeof__(addr))sign_extend64((u64)(addr), 55))
 
+#ifdef CONFIG_KASAN_SW_TAGS
+#define __tag_shifted(tag)	((u64)(tag) << 56)
+#define __tag_set(addr, tag)	(__typeof__(addr))( \
+		((u64)(addr) & ~__tag_shifted(0xff)) | __tag_shifted(tag))
+#define __tag_reset(addr)	untagged_addr(addr)
+#define __tag_get(addr)		(__u8)((u64)(addr) >> 56)
+#else
+#define __tag_set(addr, tag)	(addr)
+#define __tag_reset(addr)	(addr)
+#define __tag_get(addr)		0
+#endif
+
 /*
  * Physical vs virtual RAM address space conversion.  These are
  * private definitions which should NOT be used outside memory.h
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 7a4a0904cac8..1df536bdabcb 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -253,6 +253,8 @@ void __init kasan_init(void)
 	memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 
+	kasan_init_tags();
+
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KernelAddressSanitizer initialized\n");
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index c56af24bd3e7..a477ce2abdc9 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -169,6 +169,19 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 
 #define KASAN_SHADOW_INIT 0xFF
 
+void kasan_init_tags(void);
+
+void *kasan_reset_tag(const void *addr);
+
+#else /* CONFIG_KASAN_SW_TAGS */
+
+static inline void kasan_init_tags(void) { }
+
+static inline void *kasan_reset_tag(const void *addr)
+{
+	return (void *)addr;
+}
+
 #endif /* CONFIG_KASAN_SW_TAGS */
 
 #endif /* LINUX_KASAN_H */
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 19b950eaccff..b080b8d92812 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -8,6 +8,10 @@
 #define KASAN_SHADOW_SCALE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
 #define KASAN_SHADOW_MASK       (KASAN_SHADOW_SCALE_SIZE - 1)
 
+#define KASAN_TAG_KERNEL	0xFF /* native kernel pointers tag */
+#define KASAN_TAG_INVALID	0xFE /* inaccessible memory tag */
+#define KASAN_TAG_MAX		0xFD /* maximum value for random tags */
+
 #define KASAN_FREE_PAGE         0xFF  /* page was freed */
 #define KASAN_PAGE_REDZONE      0xFE  /* redzone for kmalloc_large allocations */
 #define KASAN_KMALLOC_REDZONE   0xFC  /* redzone inside slub object */
@@ -126,6 +130,33 @@ static inline void quarantine_reduce(void) { }
 static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
 #endif
 
+#ifdef CONFIG_KASAN_SW_TAGS
+
+u8 random_tag(void);
+
+#else
+
+static inline u8 random_tag(void)
+{
+	return 0;
+}
+
+#endif
+
+#ifndef arch_kasan_set_tag
+#define arch_kasan_set_tag(addr, tag)	((void *)(addr))
+#endif
+#ifndef arch_kasan_reset_tag
+#define arch_kasan_reset_tag(addr)	((void *)(addr))
+#endif
+#ifndef arch_kasan_get_tag
+#define arch_kasan_get_tag(addr)	0
+#endif
+
+#define set_tag(addr, tag)	((void *)arch_kasan_set_tag((addr), (tag)))
+#define reset_tag(addr)		((void *)arch_kasan_reset_tag(addr))
+#define get_tag(addr)		arch_kasan_get_tag(addr)
+
 /*
  * Exported functions for interfaces called from assembly or from generated
  * code. Declarations here to avoid warning about missing declarations.
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 04194923c543..1c4e7ce2e6fe 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -38,6 +38,43 @@
 #include "kasan.h"
 #include "../slab.h"
 
+static DEFINE_PER_CPU(u32, prng_state);
+
+void kasan_init_tags(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		per_cpu(prng_state, cpu) = get_random_u32();
+}
+
+/*
+ * If a preemption happens between this_cpu_read and this_cpu_write, the only
+ * side effect is that we'll give a few allocated in different contexts objects
+ * the same tag. Since tag-based KASAN is meant to be used a probabilistic
+ * bug-detection debug feature, this doesn't have significant negative impact.
+ *
+ * Ideally the tags use strong randomness to prevent any attempts to predict
+ * them during explicit exploit attempts. But strong randomness is expensive,
+ * and we did an intentional trade-off to use a PRNG. This non-atomic RMW
+ * sequence has in fact positive effect, since interrupts that randomly skew
+ * PRNG at unpredictable points do only good.
+ */
+u8 random_tag(void)
+{
+	u32 state = this_cpu_read(prng_state);
+
+	state = 1664525 * state + 1013904223;
+	this_cpu_write(prng_state, state);
+
+	return (u8)(state % (KASAN_TAG_MAX + 1));
+}
+
+void *kasan_reset_tag(const void *addr)
+{
+	return reset_tag(addr);
+}
+
 void check_memory_region(unsigned long addr, size_t size, bool write,
 				unsigned long ret_ip)
 {
-- 
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[PATCH v13 11/25] kasan, arm64: untag address in _virt_addr_is_linear

[Andrey Konovalov]

virt_addr_is_linear (which is used by virt_addr_valid) assumes that the
top byte of the address is 0xff, which isn't always the case with
tag-based KASAN.

This patch resets the tag in this macro.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/memory.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 83c1366a1233..5fe2353f111b 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -322,9 +322,10 @@ static inline void *phys_to_virt(phys_addr_t x)
 #endif
 #endif
 
-#define _virt_addr_is_linear(kaddr)	(((u64)(kaddr)) >= PAGE_OFFSET)
-#define virt_addr_valid(kaddr)		(_virt_addr_is_linear(kaddr) && \
-					 _virt_addr_valid(kaddr))
+#define _virt_addr_is_linear(kaddr)	\
+	(__tag_reset((u64)(kaddr)) >= PAGE_OFFSET)
+#define virt_addr_valid(kaddr)		\
+	(_virt_addr_is_linear(kaddr) && _virt_addr_valid(kaddr))
 
 #include <asm-generic/memory_model.h>
 
-- 
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[PATCH v13 12/25] kasan: preassign tags to objects with ctors or SLAB_TYPESAFE_BY_RCU

[Andrey Konovalov]

An object constructor can initialize pointers within this objects based on
the address of the object. Since the object address might be tagged, we
need to assign a tag before calling constructor.

The implemented approach is to assign tags to objects with constructors
when a slab is allocated and call constructors once as usual. The
downside is that such object would always have the same tag when it is
reallocated, so we won't catch use-after-frees on it.

Also pressign tags for objects from SLAB_TYPESAFE_BY_RCU caches, since
they can be validy accessed after having been freed.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/slab.c |  2 +-
 mm/slub.c | 24 ++++++++++++++----------
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 26f60a22e5e0..27859fb39889 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2574,7 +2574,7 @@ static void cache_init_objs(struct kmem_cache *cachep,
 
 	for (i = 0; i < cachep->num; i++) {
 		objp = index_to_obj(cachep, page, i);
-		kasan_init_slab_obj(cachep, objp);
+		objp = kasan_init_slab_obj(cachep, objp);
 
 		/* constructor could break poison info */
 		if (DEBUG == 0 && cachep->ctor) {
diff --git a/mm/slub.c b/mm/slub.c
index e739d46600b9..08740c3f3745 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1451,16 +1451,17 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
 #endif
 }
 
-static void setup_object(struct kmem_cache *s, struct page *page,
+static void *setup_object(struct kmem_cache *s, struct page *page,
 				void *object)
 {
 	setup_object_debug(s, page, object);
-	kasan_init_slab_obj(s, object);
+	object = kasan_init_slab_obj(s, object);
 	if (unlikely(s->ctor)) {
 		kasan_unpoison_object_data(s, object);
 		s->ctor(object);
 		kasan_poison_object_data(s, object);
 	}
+	return object;
 }
 
 /*
@@ -1568,16 +1569,16 @@ static bool shuffle_freelist(struct kmem_cache *s, struct page *page)
 	/* First entry is used as the base of the freelist */
 	cur = next_freelist_entry(s, page, &pos, start, page_limit,
 				freelist_count);
+	cur = setup_object(s, page, cur);
 	page->freelist = cur;
 
 	for (idx = 1; idx < page->objects; idx++) {
-		setup_object(s, page, cur);
 		next = next_freelist_entry(s, page, &pos, start, page_limit,
 			freelist_count);
+		next = setup_object(s, page, next);
 		set_freepointer(s, cur, next);
 		cur = next;
 	}
-	setup_object(s, page, cur);
 	set_freepointer(s, cur, NULL);
 
 	return true;
@@ -1599,7 +1600,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	struct page *page;
 	struct kmem_cache_order_objects oo = s->oo;
 	gfp_t alloc_gfp;
-	void *start, *p;
+	void *start, *p, *next;
 	int idx, order;
 	bool shuffle;
 
@@ -1651,13 +1652,16 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 	if (!shuffle) {
 		for_each_object_idx(p, idx, s, start, page->objects) {
-			setup_object(s, page, p);
-			if (likely(idx < page->objects))
-				set_freepointer(s, p, p + s->size);
-			else
+			if (likely(idx < page->objects)) {
+				next = p + s->size;
+				next = setup_object(s, page, next);
+				set_freepointer(s, p, next);
+			} else
 				set_freepointer(s, p, NULL);
 		}
-		page->freelist = fixup_red_left(s, start);
+		start = fixup_red_left(s, start);
+		start = setup_object(s, page, start);
+		page->freelist = start;
 	}
 
 	page->inuse = page->objects;
-- 
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[PATCH v13 13/25] kasan, arm64: fix up fault handling logic

[Andrey Konovalov]

Right now arm64 fault handling code removes pointer tags from addresses
covered by TTBR0 in faults taken from both EL0 and EL1, but doesn't do
that for pointers covered by TTBR1.

This patch adds two helper functions is_ttbr0_addr() and is_ttbr1_addr(),
where the latter one accounts for the fact that TTBR1 pointers might be
tagged when tag-based KASAN is in use, and uses these helper functions to
perform pointer checks in arch/arm64/mm/fault.c.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/fault.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 7d9571f4ae3d..c1d98f0a3086 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -40,6 +40,7 @@
 #include <asm/daifflags.h>
 #include <asm/debug-monitors.h>
 #include <asm/esr.h>
+#include <asm/kasan.h>
 #include <asm/sysreg.h>
 #include <asm/system_misc.h>
 #include <asm/pgtable.h>
@@ -132,6 +133,18 @@ static void mem_abort_decode(unsigned int esr)
 		data_abort_decode(esr);
 }
 
+static inline bool is_ttbr0_addr(unsigned long addr)
+{
+	/* entry assembly clears tags for TTBR0 addrs */
+	return addr < TASK_SIZE;
+}
+
+static inline bool is_ttbr1_addr(unsigned long addr)
+{
+	/* TTBR1 addresses may have a tag if KASAN_SW_TAGS is in use */
+	return arch_kasan_reset_tag(addr) >= VA_START;
+}
+
 /*
  * Dump out the page tables associated with 'addr' in the currently active mm.
  */
@@ -141,7 +154,7 @@ void show_pte(unsigned long addr)
 	pgd_t *pgdp;
 	pgd_t pgd;
 
-	if (addr < TASK_SIZE) {
+	if (is_ttbr0_addr(addr)) {
 		/* TTBR0 */
 		mm = current->active_mm;
 		if (mm == &init_mm) {
@@ -149,7 +162,7 @@ void show_pte(unsigned long addr)
 				 addr);
 			return;
 		}
-	} else if (addr >= VA_START) {
+	} else if (is_ttbr1_addr(addr)) {
 		/* TTBR1 */
 		mm = &init_mm;
 	} else {
@@ -254,7 +267,7 @@ static inline bool is_el1_permission_fault(unsigned long addr, unsigned int esr,
 	if (fsc_type == ESR_ELx_FSC_PERM)
 		return true;
 
-	if (addr < TASK_SIZE && system_uses_ttbr0_pan())
+	if (is_ttbr0_addr(addr) && system_uses_ttbr0_pan())
 		return fsc_type == ESR_ELx_FSC_FAULT &&
 			(regs->pstate & PSR_PAN_BIT);
 
@@ -319,7 +332,7 @@ static void set_thread_esr(unsigned long address, unsigned int esr)
 	 * type", so we ignore this wrinkle and just return the translation
 	 * fault.)
 	 */
-	if (current->thread.fault_address >= TASK_SIZE) {
+	if (!is_ttbr0_addr(current->thread.fault_address)) {
 		switch (ESR_ELx_EC(esr)) {
 		case ESR_ELx_EC_DABT_LOW:
 			/*
@@ -455,7 +468,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 		mm_flags |= FAULT_FLAG_WRITE;
 	}
 
-	if (addr < TASK_SIZE && is_el1_permission_fault(addr, esr, regs)) {
+	if (is_ttbr0_addr(addr) && is_el1_permission_fault(addr, esr, regs)) {
 		/* regs->orig_addr_limit may be 0 if we entered from EL0 */
 		if (regs->orig_addr_limit == KERNEL_DS)
 			die_kernel_fault("access to user memory with fs=KERNEL_DS",
@@ -603,7 +616,7 @@ static int __kprobes do_translation_fault(unsigned long addr,
 					  unsigned int esr,
 					  struct pt_regs *regs)
 {
-	if (addr < TASK_SIZE)
+	if (is_ttbr0_addr(addr))
 		return do_page_fault(addr, esr, regs);
 
 	do_bad_area(addr, esr, regs);
@@ -758,7 +771,7 @@ asmlinkage void __exception do_el0_ia_bp_hardening(unsigned long addr,
 	 * re-enabled IRQs. If the address is a kernel address, apply
 	 * BP hardening prior to enabling IRQs and pre-emption.
 	 */
-	if (addr > TASK_SIZE)
+	if (!is_ttbr0_addr(addr))
 		arm64_apply_bp_hardening();
 
 	local_daif_restore(DAIF_PROCCTX);
@@ -771,7 +784,7 @@ asmlinkage void __exception do_sp_pc_abort(unsigned long addr,
 					   struct pt_regs *regs)
 {
 	if (user_mode(regs)) {
-		if (instruction_pointer(regs) > TASK_SIZE)
+		if (!is_ttbr0_addr(instruction_pointer(regs)))
 			arm64_apply_bp_hardening();
 		local_daif_restore(DAIF_PROCCTX);
 	}
@@ -825,7 +838,7 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
 	if (interrupts_enabled(regs))
 		trace_hardirqs_off();
 
-	if (user_mode(regs) && instruction_pointer(regs) > TASK_SIZE)
+	if (user_mode(regs) && !is_ttbr0_addr(instruction_pointer(regs)))
 		arm64_apply_bp_hardening();
 
 	if (!inf->fn(addr, esr, regs)) {
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 14/25] kasan, arm64: enable top byte ignore for the kernel

[Andrey Konovalov]

Tag-based KASAN uses the Top Byte Ignore feature of arm64 CPUs to store a
pointer tag in the top byte of each pointer. This commit enables the
TCR_TBI1 bit, which enables Top Byte Ignore for the kernel, when tag-based
KASAN is used.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/pgtable-hwdef.h | 1 +
 arch/arm64/mm/proc.S                   | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 1d7d8da2ef9b..d43b870c39b3 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -291,6 +291,7 @@
 #define TCR_A1			(UL(1) << 22)
 #define TCR_ASID16		(UL(1) << 36)
 #define TCR_TBI0		(UL(1) << 37)
+#define TCR_TBI1		(UL(1) << 38)
 #define TCR_HA			(UL(1) << 39)
 #define TCR_HD			(UL(1) << 40)
 #define TCR_NFD1		(UL(1) << 54)
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 2c75b0b903ae..d861f208eeb1 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -47,6 +47,12 @@
 /* PTWs cacheable, inner/outer WBWA */
 #define TCR_CACHE_FLAGS	TCR_IRGN_WBWA | TCR_ORGN_WBWA
 
+#ifdef CONFIG_KASAN_SW_TAGS
+#define TCR_KASAN_FLAGS TCR_TBI1
+#else
+#define TCR_KASAN_FLAGS 0
+#endif
+
 #define MAIR(attr, mt)	((attr) << ((mt) * 8))
 
 /*
@@ -445,7 +451,7 @@ ENTRY(__cpu_setup)
 	 */
 	ldr	x10, =TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
 			TCR_TG_FLAGS | TCR_KASLR_FLAGS | TCR_ASID16 | \
-			TCR_TBI0 | TCR_A1
+			TCR_TBI0 | TCR_A1 | TCR_KASAN_FLAGS
 	tcr_set_idmap_t0sz	x10, x9
 
 	/*
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 15/25] kasan, mm: perform untagged pointers comparison in krealloc

[Andrey Konovalov]

The krealloc function checks where the same buffer was reused or a new one
allocated by comparing kernel pointers. Tag-based KASAN changes memory tag
on the krealloc'ed chunk of memory and therefore also changes the pointer
tag of the returned pointer. Therefore we need to perform comparison on
untagged (with tags reset) pointers to check whether it's the same memory
region or not.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/slab_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 5f3504e26d4c..5aabcbd32d82 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1534,7 +1534,7 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags)
 	}
 
 	ret = __do_krealloc(p, new_size, flags);
-	if (ret && p != ret)
+	if (ret && kasan_reset_tag(p) != kasan_reset_tag(ret))
 		kfree(p);
 
 	return ret;
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 16/25] kasan: split out generic_report.c from report.c

[Andrey Konovalov]

This patch moves generic KASAN specific error reporting routines to
generic_report.c without any functional changes, leaving common error
reporting code in report.c to be later reused by tag-based KASAN.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/Makefile         |   4 +-
 mm/kasan/generic_report.c | 158 +++++++++++++++++++++++++
 mm/kasan/kasan.h          |   7 ++
 mm/kasan/report.c         | 234 +++++++++-----------------------------
 mm/kasan/tags_report.c    |  39 +++++++
 5 files changed, 257 insertions(+), 185 deletions(-)
 create mode 100644 mm/kasan/generic_report.c
 create mode 100644 mm/kasan/tags_report.c

diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 68ba1822f003..0a14fcff70ed 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -14,5 +14,5 @@ CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
 obj-$(CONFIG_KASAN) := common.o init.o report.o
-obj-$(CONFIG_KASAN_GENERIC) += generic.o quarantine.o
-obj-$(CONFIG_KASAN_SW_TAGS) += tags.o
+obj-$(CONFIG_KASAN_GENERIC) += generic.o generic_report.o quarantine.o
+obj-$(CONFIG_KASAN_SW_TAGS) += tags.o tags_report.o
diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
new file mode 100644
index 000000000000..5201d1770700
--- /dev/null
+++ b/mm/kasan/generic_report.c
@@ -0,0 +1,158 @@
+/*
+ * This file contains generic KASAN specific error reporting code.
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
+ *
+ * Some code borrowed from https://github.com/xairy/kasan-prototype by
+ *        Andrey Konovalov <andreyknvl@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/bitops.h>
+#include <linux/ftrace.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/printk.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/stackdepot.h>
+#include <linux/stacktrace.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/kasan.h>
+#include <linux/module.h>
+
+#include <asm/sections.h>
+
+#include "kasan.h"
+#include "../slab.h"
+
+static const void *find_first_bad_addr(const void *addr, size_t size)
+{
+	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
+	const void *first_bad_addr = addr;
+
+	while (!shadow_val && first_bad_addr < addr + size) {
+		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
+		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
+	}
+	return first_bad_addr;
+}
+
+static const char *get_shadow_bug_type(struct kasan_access_info *info)
+{
+	const char *bug_type = "unknown-crash";
+	u8 *shadow_addr;
+
+	info->first_bad_addr = find_first_bad_addr(info->access_addr,
+						info->access_size);
+
+	shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
+
+	/*
+	 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
+	 * at the next shadow byte to determine the type of the bad access.
+	 */
+	if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
+		shadow_addr++;
+
+	switch (*shadow_addr) {
+	case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
+		/*
+		 * In theory it's still possible to see these shadow values
+		 * due to a data race in the kernel code.
+		 */
+		bug_type = "out-of-bounds";
+		break;
+	case KASAN_PAGE_REDZONE:
+	case KASAN_KMALLOC_REDZONE:
+		bug_type = "slab-out-of-bounds";
+		break;
+	case KASAN_GLOBAL_REDZONE:
+		bug_type = "global-out-of-bounds";
+		break;
+	case KASAN_STACK_LEFT:
+	case KASAN_STACK_MID:
+	case KASAN_STACK_RIGHT:
+	case KASAN_STACK_PARTIAL:
+		bug_type = "stack-out-of-bounds";
+		break;
+	case KASAN_FREE_PAGE:
+	case KASAN_KMALLOC_FREE:
+		bug_type = "use-after-free";
+		break;
+	case KASAN_USE_AFTER_SCOPE:
+		bug_type = "use-after-scope";
+		break;
+	case KASAN_ALLOCA_LEFT:
+	case KASAN_ALLOCA_RIGHT:
+		bug_type = "alloca-out-of-bounds";
+		break;
+	}
+
+	return bug_type;
+}
+
+static const char *get_wild_bug_type(struct kasan_access_info *info)
+{
+	const char *bug_type = "unknown-crash";
+
+	if ((unsigned long)info->access_addr < PAGE_SIZE)
+		bug_type = "null-ptr-deref";
+	else if ((unsigned long)info->access_addr < TASK_SIZE)
+		bug_type = "user-memory-access";
+	else
+		bug_type = "wild-memory-access";
+
+	return bug_type;
+}
+
+const char *get_bug_type(struct kasan_access_info *info)
+{
+	if (addr_has_shadow(info->access_addr))
+		return get_shadow_bug_type(info);
+	return get_wild_bug_type(info);
+}
+
+#define DEFINE_ASAN_REPORT_LOAD(size)                     \
+void __asan_report_load##size##_noabort(unsigned long addr) \
+{                                                         \
+	kasan_report(addr, size, false, _RET_IP_);	  \
+}                                                         \
+EXPORT_SYMBOL(__asan_report_load##size##_noabort)
+
+#define DEFINE_ASAN_REPORT_STORE(size)                     \
+void __asan_report_store##size##_noabort(unsigned long addr) \
+{                                                          \
+	kasan_report(addr, size, true, _RET_IP_);	   \
+}                                                          \
+EXPORT_SYMBOL(__asan_report_store##size##_noabort)
+
+DEFINE_ASAN_REPORT_LOAD(1);
+DEFINE_ASAN_REPORT_LOAD(2);
+DEFINE_ASAN_REPORT_LOAD(4);
+DEFINE_ASAN_REPORT_LOAD(8);
+DEFINE_ASAN_REPORT_LOAD(16);
+DEFINE_ASAN_REPORT_STORE(1);
+DEFINE_ASAN_REPORT_STORE(2);
+DEFINE_ASAN_REPORT_STORE(4);
+DEFINE_ASAN_REPORT_STORE(8);
+DEFINE_ASAN_REPORT_STORE(16);
+
+void __asan_report_load_n_noabort(unsigned long addr, size_t size)
+{
+	kasan_report(addr, size, false, _RET_IP_);
+}
+EXPORT_SYMBOL(__asan_report_load_n_noabort);
+
+void __asan_report_store_n_noabort(unsigned long addr, size_t size)
+{
+	kasan_report(addr, size, true, _RET_IP_);
+}
+EXPORT_SYMBOL(__asan_report_store_n_noabort);
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index b080b8d92812..33cc3b0e017e 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -109,11 +109,18 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 		<< KASAN_SHADOW_SCALE_SHIFT);
 }
 
+static inline bool addr_has_shadow(const void *addr)
+{
+	return (addr >= kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
+}
+
 void kasan_poison_shadow(const void *address, size_t size, u8 value);
 
 void check_memory_region(unsigned long addr, size_t size, bool write,
 				unsigned long ret_ip);
 
+const char *get_bug_type(struct kasan_access_info *info);
+
 void kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 void kasan_report_invalid_free(void *object, unsigned long ip);
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 5c169aa688fd..64a74f334c45 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -1,5 +1,5 @@
 /*
- * This file contains error reporting code.
+ * This file contains common generic and tag-based KASAN error reporting code.
  *
  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
@@ -39,103 +39,34 @@
 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
 #define SHADOW_ROWS_AROUND_ADDR 2
 
-static const void *find_first_bad_addr(const void *addr, size_t size)
-{
-	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
-	const void *first_bad_addr = addr;
-
-	while (!shadow_val && first_bad_addr < addr + size) {
-		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
-		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
-	}
-	return first_bad_addr;
-}
+static unsigned long kasan_flags;
 
-static bool addr_has_shadow(struct kasan_access_info *info)
-{
-	return (info->access_addr >=
-		kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
-}
+#define KASAN_BIT_REPORTED	0
+#define KASAN_BIT_MULTI_SHOT	1
 
-static const char *get_shadow_bug_type(struct kasan_access_info *info)
+bool kasan_save_enable_multi_shot(void)
 {
-	const char *bug_type = "unknown-crash";
-	u8 *shadow_addr;
-
-	info->first_bad_addr = find_first_bad_addr(info->access_addr,
-						info->access_size);
-
-	shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
-
-	/*
-	 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
-	 * at the next shadow byte to determine the type of the bad access.
-	 */
-	if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
-		shadow_addr++;
-
-	switch (*shadow_addr) {
-	case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
-		/*
-		 * In theory it's still possible to see these shadow values
-		 * due to a data race in the kernel code.
-		 */
-		bug_type = "out-of-bounds";
-		break;
-	case KASAN_PAGE_REDZONE:
-	case KASAN_KMALLOC_REDZONE:
-		bug_type = "slab-out-of-bounds";
-		break;
-	case KASAN_GLOBAL_REDZONE:
-		bug_type = "global-out-of-bounds";
-		break;
-	case KASAN_STACK_LEFT:
-	case KASAN_STACK_MID:
-	case KASAN_STACK_RIGHT:
-	case KASAN_STACK_PARTIAL:
-		bug_type = "stack-out-of-bounds";
-		break;
-	case KASAN_FREE_PAGE:
-	case KASAN_KMALLOC_FREE:
-		bug_type = "use-after-free";
-		break;
-	case KASAN_USE_AFTER_SCOPE:
-		bug_type = "use-after-scope";
-		break;
-	case KASAN_ALLOCA_LEFT:
-	case KASAN_ALLOCA_RIGHT:
-		bug_type = "alloca-out-of-bounds";
-		break;
-	}
-
-	return bug_type;
+	return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 }
+EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
 
-static const char *get_wild_bug_type(struct kasan_access_info *info)
+void kasan_restore_multi_shot(bool enabled)
 {
-	const char *bug_type = "unknown-crash";
-
-	if ((unsigned long)info->access_addr < PAGE_SIZE)
-		bug_type = "null-ptr-deref";
-	else if ((unsigned long)info->access_addr < TASK_SIZE)
-		bug_type = "user-memory-access";
-	else
-		bug_type = "wild-memory-access";
-
-	return bug_type;
+	if (!enabled)
+		clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 }
+EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
 
-static const char *get_bug_type(struct kasan_access_info *info)
+static int __init kasan_set_multi_shot(char *str)
 {
-	if (addr_has_shadow(info))
-		return get_shadow_bug_type(info);
-	return get_wild_bug_type(info);
+	set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
+	return 1;
 }
+__setup("kasan_multi_shot", kasan_set_multi_shot);
 
-static void print_error_description(struct kasan_access_info *info)
+static void print_error_description(struct kasan_access_info *info,
+					const char *bug_type)
 {
-	const char *bug_type = get_bug_type(info);
-
 	pr_err("BUG: KASAN: %s in %pS\n",
 		bug_type, (void *)info->ip);
 	pr_err("%s of size %zu at addr %px by task %s/%d\n",
@@ -143,25 +74,9 @@ static void print_error_description(struct kasan_access_info *info)
 		info->access_addr, current->comm, task_pid_nr(current));
 }
 
-static inline bool kernel_or_module_addr(const void *addr)
-{
-	if (addr >= (void *)_stext && addr < (void *)_end)
-		return true;
-	if (is_module_address((unsigned long)addr))
-		return true;
-	return false;
-}
-
-static inline bool init_task_stack_addr(const void *addr)
-{
-	return addr >= (void *)&init_thread_union.stack &&
-		(addr <= (void *)&init_thread_union.stack +
-			sizeof(init_thread_union.stack));
-}
-
 static DEFINE_SPINLOCK(report_lock);
 
-static void kasan_start_report(unsigned long *flags)
+static void start_report(unsigned long *flags)
 {
 	/*
 	 * Make sure we don't end up in loop.
@@ -171,7 +86,7 @@ static void kasan_start_report(unsigned long *flags)
 	pr_err("==================================================================\n");
 }
 
-static void kasan_end_report(unsigned long *flags)
+static void end_report(unsigned long *flags)
 {
 	pr_err("==================================================================\n");
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
@@ -249,6 +164,22 @@ static void describe_object(struct kmem_cache *cache, void *object,
 	describe_object_addr(cache, object, addr);
 }
 
+static inline bool kernel_or_module_addr(const void *addr)
+{
+	if (addr >= (void *)_stext && addr < (void *)_end)
+		return true;
+	if (is_module_address((unsigned long)addr))
+		return true;
+	return false;
+}
+
+static inline bool init_task_stack_addr(const void *addr)
+{
+	return addr >= (void *)&init_thread_union.stack &&
+		(addr <= (void *)&init_thread_union.stack +
+			sizeof(init_thread_union.stack));
+}
+
 static void print_address_description(void *addr)
 {
 	struct page *page = addr_to_page(addr);
@@ -326,29 +257,38 @@ static void print_shadow_for_address(const void *addr)
 	}
 }
 
+static bool report_enabled(void)
+{
+	if (current->kasan_depth)
+		return false;
+	if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
+		return true;
+	return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
+}
+
 void kasan_report_invalid_free(void *object, unsigned long ip)
 {
 	unsigned long flags;
 
-	kasan_start_report(&flags);
+	start_report(&flags);
 	pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 	pr_err("\n");
 	print_address_description(object);
 	pr_err("\n");
 	print_shadow_for_address(object);
-	kasan_end_report(&flags);
+	end_report(&flags);
 }
 
 static void kasan_report_error(struct kasan_access_info *info)
 {
 	unsigned long flags;
 
-	kasan_start_report(&flags);
+	start_report(&flags);
 
-	print_error_description(info);
+	print_error_description(info, get_bug_type(info));
 	pr_err("\n");
 
-	if (!addr_has_shadow(info)) {
+	if (!addr_has_shadow(info->access_addr)) {
 		dump_stack();
 	} else {
 		print_address_description((void *)info->access_addr);
@@ -356,41 +296,7 @@ static void kasan_report_error(struct kasan_access_info *info)
 		print_shadow_for_address(info->first_bad_addr);
 	}
 
-	kasan_end_report(&flags);
-}
-
-static unsigned long kasan_flags;
-
-#define KASAN_BIT_REPORTED	0
-#define KASAN_BIT_MULTI_SHOT	1
-
-bool kasan_save_enable_multi_shot(void)
-{
-	return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
-}
-EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
-
-void kasan_restore_multi_shot(bool enabled)
-{
-	if (!enabled)
-		clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
-}
-EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
-
-static int __init kasan_set_multi_shot(char *str)
-{
-	set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
-	return 1;
-}
-__setup("kasan_multi_shot", kasan_set_multi_shot);
-
-static inline bool kasan_report_enabled(void)
-{
-	if (current->kasan_depth)
-		return false;
-	if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
-		return true;
-	return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
+	end_report(&flags);
 }
 
 void kasan_report(unsigned long addr, size_t size,
@@ -398,7 +304,7 @@ void kasan_report(unsigned long addr, size_t size,
 {
 	struct kasan_access_info info;
 
-	if (likely(!kasan_report_enabled()))
+	if (likely(!report_enabled()))
 		return;
 
 	disable_trace_on_warning();
@@ -411,41 +317,3 @@ void kasan_report(unsigned long addr, size_t size,
 
 	kasan_report_error(&info);
 }
-
-
-#define DEFINE_ASAN_REPORT_LOAD(size)                     \
-void __asan_report_load##size##_noabort(unsigned long addr) \
-{                                                         \
-	kasan_report(addr, size, false, _RET_IP_);	  \
-}                                                         \
-EXPORT_SYMBOL(__asan_report_load##size##_noabort)
-
-#define DEFINE_ASAN_REPORT_STORE(size)                     \
-void __asan_report_store##size##_noabort(unsigned long addr) \
-{                                                          \
-	kasan_report(addr, size, true, _RET_IP_);	   \
-}                                                          \
-EXPORT_SYMBOL(__asan_report_store##size##_noabort)
-
-DEFINE_ASAN_REPORT_LOAD(1);
-DEFINE_ASAN_REPORT_LOAD(2);
-DEFINE_ASAN_REPORT_LOAD(4);
-DEFINE_ASAN_REPORT_LOAD(8);
-DEFINE_ASAN_REPORT_LOAD(16);
-DEFINE_ASAN_REPORT_STORE(1);
-DEFINE_ASAN_REPORT_STORE(2);
-DEFINE_ASAN_REPORT_STORE(4);
-DEFINE_ASAN_REPORT_STORE(8);
-DEFINE_ASAN_REPORT_STORE(16);
-
-void __asan_report_load_n_noabort(unsigned long addr, size_t size)
-{
-	kasan_report(addr, size, false, _RET_IP_);
-}
-EXPORT_SYMBOL(__asan_report_load_n_noabort);
-
-void __asan_report_store_n_noabort(unsigned long addr, size_t size)
-{
-	kasan_report(addr, size, true, _RET_IP_);
-}
-EXPORT_SYMBOL(__asan_report_store_n_noabort);
diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
new file mode 100644
index 000000000000..8af15e87d3bc
--- /dev/null
+++ b/mm/kasan/tags_report.c
@@ -0,0 +1,39 @@
+/*
+ * This file contains tag-based KASAN specific error reporting code.
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
+ *
+ * Some code borrowed from https://github.com/xairy/kasan-prototype by
+ *        Andrey Konovalov <andreyknvl@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/bitops.h>
+#include <linux/ftrace.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/printk.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/stackdepot.h>
+#include <linux/stacktrace.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/kasan.h>
+#include <linux/module.h>
+
+#include <asm/sections.h>
+
+#include "kasan.h"
+#include "../slab.h"
+
+const char *get_bug_type(struct kasan_access_info *info)
+{
+	return "invalid-access";
+}
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 17/25] kasan: add bug reporting routines for tag-based mode

[Andrey Konovalov]

This commit adds rountines, that print tag-based KASAN error reports.
Those are quite similar to generic KASAN, the difference is:

1. The way tag-based KASAN finds the first bad shadow cell (with a
   mismatching tag). Tag-based KASAN compares memory tags from the shadow
   memory to the pointer tag.

2. Tag-based KASAN reports all bugs with the "KASAN: invalid-access"
   header.

Also simplify generic KASAN find_first_bad_addr.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/generic_report.c | 16 ++++-------
 mm/kasan/kasan.h          |  5 ++++
 mm/kasan/report.c         | 57 +++++++++++++++++++++------------------
 mm/kasan/tags_report.c    | 18 +++++++++++++
 4 files changed, 59 insertions(+), 37 deletions(-)

diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index 5201d1770700..a4604cceae59 100644
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -33,16 +33,13 @@
 #include "kasan.h"
 #include "../slab.h"
 
-static const void *find_first_bad_addr(const void *addr, size_t size)
+void *find_first_bad_addr(void *addr, size_t size)
 {
-	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
-	const void *first_bad_addr = addr;
+	void *p = addr;
 
-	while (!shadow_val && first_bad_addr < addr + size) {
-		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
-		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
-	}
-	return first_bad_addr;
+	while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
+		p += KASAN_SHADOW_SCALE_SIZE;
+	return p;
 }
 
 static const char *get_shadow_bug_type(struct kasan_access_info *info)
@@ -50,9 +47,6 @@ static const char *get_shadow_bug_type(struct kasan_access_info *info)
 	const char *bug_type = "unknown-crash";
 	u8 *shadow_addr;
 
-	info->first_bad_addr = find_first_bad_addr(info->access_addr,
-						info->access_size);
-
 	shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
 
 	/*
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 33cc3b0e017e..82a23b23ff93 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -119,6 +119,7 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value);
 void check_memory_region(unsigned long addr, size_t size, bool write,
 				unsigned long ret_ip);
 
+void *find_first_bad_addr(void *addr, size_t size);
 const char *get_bug_type(struct kasan_access_info *info);
 
 void kasan_report(unsigned long addr, size_t size,
@@ -139,10 +140,14 @@ static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
 
 #ifdef CONFIG_KASAN_SW_TAGS
 
+void print_tags(u8 addr_tag, const void *addr);
+
 u8 random_tag(void);
 
 #else
 
+static inline void print_tags(u8 addr_tag, const void *addr) { }
+
 static inline u8 random_tag(void)
 {
 	return 0;
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 64a74f334c45..214d85035f99 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -64,11 +64,10 @@ static int __init kasan_set_multi_shot(char *str)
 }
 __setup("kasan_multi_shot", kasan_set_multi_shot);
 
-static void print_error_description(struct kasan_access_info *info,
-					const char *bug_type)
+static void print_error_description(struct kasan_access_info *info)
 {
 	pr_err("BUG: KASAN: %s in %pS\n",
-		bug_type, (void *)info->ip);
+		get_bug_type(info), (void *)info->ip);
 	pr_err("%s of size %zu at addr %px by task %s/%d\n",
 		info->is_write ? "Write" : "Read", info->access_size,
 		info->access_addr, current->comm, task_pid_nr(current));
@@ -272,6 +271,8 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
 
 	start_report(&flags);
 	pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
+	print_tags(get_tag(object), reset_tag(object));
+	object = reset_tag(object);
 	pr_err("\n");
 	print_address_description(object);
 	pr_err("\n");
@@ -279,41 +280,45 @@ void kasan_report_invalid_free(void *object, unsigned long ip)
 	end_report(&flags);
 }
 
-static void kasan_report_error(struct kasan_access_info *info)
-{
-	unsigned long flags;
-
-	start_report(&flags);
-
-	print_error_description(info, get_bug_type(info));
-	pr_err("\n");
-
-	if (!addr_has_shadow(info->access_addr)) {
-		dump_stack();
-	} else {
-		print_address_description((void *)info->access_addr);
-		pr_err("\n");
-		print_shadow_for_address(info->first_bad_addr);
-	}
-
-	end_report(&flags);
-}
-
 void kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip)
 {
 	struct kasan_access_info info;
+	void *tagged_addr;
+	void *untagged_addr;
+	unsigned long flags;
 
 	if (likely(!report_enabled()))
 		return;
 
 	disable_trace_on_warning();
 
-	info.access_addr = (void *)addr;
-	info.first_bad_addr = (void *)addr;
+	tagged_addr = (void *)addr;
+	untagged_addr = reset_tag(tagged_addr);
+
+	info.access_addr = tagged_addr;
+	if (addr_has_shadow(untagged_addr))
+		info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
+	else
+		info.first_bad_addr = untagged_addr;
 	info.access_size = size;
 	info.is_write = is_write;
 	info.ip = ip;
 
-	kasan_report_error(&info);
+	start_report(&flags);
+
+	print_error_description(&info);
+	if (addr_has_shadow(untagged_addr))
+		print_tags(get_tag(tagged_addr), info.first_bad_addr);
+	pr_err("\n");
+
+	if (addr_has_shadow(untagged_addr)) {
+		print_address_description(untagged_addr);
+		pr_err("\n");
+		print_shadow_for_address(info.first_bad_addr);
+	} else {
+		dump_stack();
+	}
+
+	end_report(&flags);
 }
diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
index 8af15e87d3bc..573c51d20d09 100644
--- a/mm/kasan/tags_report.c
+++ b/mm/kasan/tags_report.c
@@ -37,3 +37,21 @@ const char *get_bug_type(struct kasan_access_info *info)
 {
 	return "invalid-access";
 }
+
+void *find_first_bad_addr(void *addr, size_t size)
+{
+	u8 tag = get_tag(addr);
+	void *p = reset_tag(addr);
+	void *end = p + size;
+
+	while (p < end && tag == *(u8 *)kasan_mem_to_shadow(p))
+		p += KASAN_SHADOW_SCALE_SIZE;
+	return p;
+}
+
+void print_tags(u8 addr_tag, const void *addr)
+{
+	u8 *shadow = (u8 *)kasan_mem_to_shadow(addr);
+
+	pr_err("Pointer tag: [%02x], memory tag: [%02x]\n", addr_tag, *shadow);
+}
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 18/25] mm: move obj_to_index to include/linux/slab_def.h

[Andrey Konovalov]

While with SLUB we can actually preassign tags for caches with contructors
and store them in pointers in the freelist, SLAB doesn't allow that since
the freelist is stored as an array of indexes, so there are no pointers to
store the tags.

Instead we compute the tag twice, once when a slab is created before
calling the constructor and then again each time when an object is
allocated with kmalloc. Tag is computed simply by taking the lowest byte of
the index that corresponds to the object. However in kasan_kmalloc we only
have access to the objects pointer, so we need a way to find out which
index this object corresponds to.

This patch moves obj_to_index from slab.c to include/linux/slab_def.h to
be reused by KASAN.

Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/slab_def.h | 13 +++++++++++++
 mm/slab.c                | 13 -------------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 3485c58cfd1c..9a5eafb7145b 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -104,4 +104,17 @@ static inline void *nearest_obj(struct kmem_cache *cache, struct page *page,
 		return object;
 }
 
+/*
+ * We want to avoid an expensive divide : (offset / cache->size)
+ *   Using the fact that size is a constant for a particular cache,
+ *   we can replace (offset / cache->size) by
+ *   reciprocal_divide(offset, cache->reciprocal_buffer_size)
+ */
+static inline unsigned int obj_to_index(const struct kmem_cache *cache,
+					const struct page *page, void *obj)
+{
+	u32 offset = (obj - page->s_mem);
+	return reciprocal_divide(offset, cache->reciprocal_buffer_size);
+}
+
 #endif	/* _LINUX_SLAB_DEF_H */
diff --git a/mm/slab.c b/mm/slab.c
index 27859fb39889..d2f827316dfc 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -406,19 +406,6 @@ static inline void *index_to_obj(struct kmem_cache *cache, struct page *page,
 	return page->s_mem + cache->size * idx;
 }
 
-/*
- * We want to avoid an expensive divide : (offset / cache->size)
- *   Using the fact that size is a constant for a particular cache,
- *   we can replace (offset / cache->size) by
- *   reciprocal_divide(offset, cache->reciprocal_buffer_size)
- */
-static inline unsigned int obj_to_index(const struct kmem_cache *cache,
-					const struct page *page, void *obj)
-{
-	u32 offset = (obj - page->s_mem);
-	return reciprocal_divide(offset, cache->reciprocal_buffer_size);
-}
-
 #define BOOT_CPUCACHE_ENTRIES	1
 /* internal cache of cache description objs */
 static struct kmem_cache kmem_cache_boot = {
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Andrey Konovalov]

This commit adds tag-based KASAN specific hooks implementation and
adjusts common generic and tag-based KASAN ones.

1. When a new slab cache is created, tag-based KASAN rounds up the size of
   the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16).

2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow
   memory, that corresponds to this object to this tag, and embeds this
   tag value into the top byte of the returned pointer.

3. On each kfree tag-based KASAN poisons the shadow memory with a random
   tag to allow detection of use-after-free bugs.

The rest of the logic of the hook implementation is very much similar to
the one provided by generic KASAN. Tag-based KASAN saves allocation and
free stack metadata to the slab object the same way generic KASAN does.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++--------
 mm/kasan/kasan.h  |   8 ++++
 mm/kasan/tags.c   |  48 +++++++++++++++++++
 3 files changed, 153 insertions(+), 19 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 7134e75447ff..27f0cae336c9 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -140,6 +140,13 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value)
 {
 	void *shadow_start, *shadow_end;
 
+	/*
+	 * Perform shadow offset calculation based on untagged address, as
+	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
+	 * addresses to this function.
+	 */
+	address = reset_tag(address);
+
 	shadow_start = kasan_mem_to_shadow(address);
 	shadow_end = kasan_mem_to_shadow(address + size);
 
@@ -148,11 +155,24 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value)
 
 void kasan_unpoison_shadow(const void *address, size_t size)
 {
-	kasan_poison_shadow(address, size, 0);
+	u8 tag = get_tag(address);
+
+	/*
+	 * Perform shadow offset calculation based on untagged address, as
+	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
+	 * addresses to this function.
+	 */
+	address = reset_tag(address);
+
+	kasan_poison_shadow(address, size, tag);
 
 	if (size & KASAN_SHADOW_MASK) {
 		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
-		*shadow = size & KASAN_SHADOW_MASK;
+
+		if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+			*shadow = tag;
+		else
+			*shadow = size & KASAN_SHADOW_MASK;
 	}
 }
 
@@ -200,8 +220,9 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
 
 void kasan_alloc_pages(struct page *page, unsigned int order)
 {
-	if (likely(!PageHighMem(page)))
-		kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
+	if (unlikely(PageHighMem(page)))
+		return;
+	kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 }
 
 void kasan_free_pages(struct page *page, unsigned int order)
@@ -218,6 +239,9 @@ void kasan_free_pages(struct page *page, unsigned int order)
  */
 static inline unsigned int optimal_redzone(unsigned int object_size)
 {
+	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+		return 0;
+
 	return
 		object_size <= 64        - 16   ? 16 :
 		object_size <= 128       - 32   ? 32 :
@@ -232,6 +256,7 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 			slab_flags_t *flags)
 {
 	unsigned int orig_size = *size;
+	unsigned int redzone_size;
 	int redzone_adjust;
 
 	/* Add alloc meta. */
@@ -239,20 +264,20 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 	*size += sizeof(struct kasan_alloc_meta);
 
 	/* Add free meta. */
-	if (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
-	    cache->object_size < sizeof(struct kasan_free_meta)) {
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
+	    (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
+	     cache->object_size < sizeof(struct kasan_free_meta))) {
 		cache->kasan_info.free_meta_offset = *size;
 		*size += sizeof(struct kasan_free_meta);
 	}
-	redzone_adjust = optimal_redzone(cache->object_size) -
-		(*size - cache->object_size);
 
+	redzone_size = optimal_redzone(cache->object_size);
+	redzone_adjust = redzone_size -	(*size - cache->object_size);
 	if (redzone_adjust > 0)
 		*size += redzone_adjust;
 
 	*size = min_t(unsigned int, KMALLOC_MAX_SIZE,
-			max(*size, cache->object_size +
-					optimal_redzone(cache->object_size)));
+			max(*size, cache->object_size + redzone_size));
 
 	/*
 	 * If the metadata doesn't fit, don't enable KASAN at all.
@@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 		return;
 	}
 
+	cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
+
 	*flags |= SLAB_KASAN;
 }
 
@@ -309,6 +336,32 @@ void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 			KASAN_KMALLOC_REDZONE);
 }
 
+/*
+ * Since it's desirable to only call object contructors once during slab
+ * allocation, we preassign tags to all such objects. Also preassign tags for
+ * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports.
+ * For SLAB allocator we can't preassign tags randomly since the freelist is
+ * stored as an array of indexes instead of a linked list. Assign tags based
+ * on objects indexes, so that objects that are next to each other get
+ * different tags.
+ * After a tag is assigned, the object always gets allocated with the same tag.
+ * The reason is that we can't change tags for objects with constructors on
+ * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor
+ * code can save the pointer to the object somewhere (e.g. in the object
+ * itself). Then if we retag it, the old saved pointer will become invalid.
+ */
+static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new)
+{
+	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
+		return new ? KASAN_TAG_KERNEL : random_tag();
+
+#ifdef CONFIG_SLAB
+	return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
+#else
+	return new ? random_tag() : get_tag(object);
+#endif
+}
+
 void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 {
 	struct kasan_alloc_meta *alloc_info;
@@ -319,6 +372,9 @@ void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 	alloc_info = get_alloc_info(cache, object);
 	__memset(alloc_info, 0, sizeof(*alloc_info));
 
+	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+		object = set_tag(object, assign_tag(cache, object, true));
+
 	return (void *)object;
 }
 
@@ -327,15 +383,30 @@ void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
 	return kasan_kmalloc(cache, object, cache->object_size, flags);
 }
 
+static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
+{
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		return shadow_byte < 0 ||
+			shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
+	else
+		return tag != (u8)shadow_byte;
+}
+
 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 			      unsigned long ip, bool quarantine)
 {
 	s8 shadow_byte;
+	u8 tag;
+	void *tagged_object;
 	unsigned long rounded_up_size;
 
+	tag = get_tag(object);
+	tagged_object = object;
+	object = reset_tag(object);
+
 	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
 	    object)) {
-		kasan_report_invalid_free(object, ip);
+		kasan_report_invalid_free(tagged_object, ip);
 		return true;
 	}
 
@@ -344,20 +415,22 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 		return false;
 
 	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
-	if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
-		kasan_report_invalid_free(object, ip);
+	if (shadow_invalid(tag, shadow_byte)) {
+		kasan_report_invalid_free(tagged_object, ip);
 		return true;
 	}
 
 	rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
 	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 
-	if (!quarantine || unlikely(!(cache->flags & SLAB_KASAN)))
+	if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
+			unlikely(!(cache->flags & SLAB_KASAN)))
 		return false;
 
 	set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
 	quarantine_put(get_free_info(cache, object), cache);
-	return true;
+
+	return IS_ENABLED(CONFIG_KASAN_GENERIC);
 }
 
 bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
@@ -370,6 +443,7 @@ void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 {
 	unsigned long redzone_start;
 	unsigned long redzone_end;
+	u8 tag;
 
 	if (gfpflags_allow_blocking(flags))
 		quarantine_reduce();
@@ -382,14 +456,18 @@ void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 	redzone_end = round_up((unsigned long)object + cache->object_size,
 				KASAN_SHADOW_SCALE_SIZE);
 
-	kasan_unpoison_shadow(object, size);
+	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
+		tag = assign_tag(cache, object, false);
+
+	/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
+	kasan_unpoison_shadow(set_tag(object, tag), size);
 	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 		KASAN_KMALLOC_REDZONE);
 
 	if (cache->flags & SLAB_KASAN)
 		set_track(&get_alloc_info(cache, object)->alloc_track, flags);
 
-	return (void *)object;
+	return set_tag(object, tag);
 }
 EXPORT_SYMBOL(kasan_kmalloc);
 
@@ -439,7 +517,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip)
 	page = virt_to_head_page(ptr);
 
 	if (unlikely(!PageSlab(page))) {
-		if (ptr != page_address(page)) {
+		if (reset_tag(ptr) != page_address(page)) {
 			kasan_report_invalid_free(ptr, ip);
 			return;
 		}
@@ -452,7 +530,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip)
 
 void kasan_kfree_large(void *ptr, unsigned long ip)
 {
-	if (ptr != page_address(virt_to_head_page(ptr)))
+	if (reset_tag(ptr) != page_address(virt_to_head_page(ptr)))
 		kasan_report_invalid_free(ptr, ip);
 	/* The object will be poisoned by page_alloc. */
 }
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 82a23b23ff93..ea51b2d898ec 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -12,10 +12,18 @@
 #define KASAN_TAG_INVALID	0xFE /* inaccessible memory tag */
 #define KASAN_TAG_MAX		0xFD /* maximum value for random tags */
 
+#ifdef CONFIG_KASAN_GENERIC
 #define KASAN_FREE_PAGE         0xFF  /* page was freed */
 #define KASAN_PAGE_REDZONE      0xFE  /* redzone for kmalloc_large allocations */
 #define KASAN_KMALLOC_REDZONE   0xFC  /* redzone inside slub object */
 #define KASAN_KMALLOC_FREE      0xFB  /* object was freed (kmem_cache_free/kfree) */
+#else
+#define KASAN_FREE_PAGE         KASAN_TAG_INVALID
+#define KASAN_PAGE_REDZONE      KASAN_TAG_INVALID
+#define KASAN_KMALLOC_REDZONE   KASAN_TAG_INVALID
+#define KASAN_KMALLOC_FREE      KASAN_TAG_INVALID
+#endif
+
 #define KASAN_GLOBAL_REDZONE    0xFA  /* redzone for global variable */
 
 /*
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 1c4e7ce2e6fe..1d1b79350e28 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -78,15 +78,60 @@ void *kasan_reset_tag(const void *addr)
 void check_memory_region(unsigned long addr, size_t size, bool write,
 				unsigned long ret_ip)
 {
+	u8 tag;
+	u8 *shadow_first, *shadow_last, *shadow;
+	void *untagged_addr;
+
+	if (unlikely(size == 0))
+		return;
+
+	tag = get_tag((const void *)addr);
+
+	/*
+	 * Ignore accesses for pointers tagged with 0xff (native kernel
+	 * pointer tag) to suppress false positives caused by kmap.
+	 *
+	 * Some kernel code was written to account for archs that don't keep
+	 * high memory mapped all the time, but rather map and unmap particular
+	 * pages when needed. Instead of storing a pointer to the kernel memory,
+	 * this code saves the address of the page structure and offset within
+	 * that page for later use. Those pages are then mapped and unmapped
+	 * with kmap/kunmap when necessary and virt_to_page is used to get the
+	 * virtual address of the page. For arm64 (that keeps the high memory
+	 * mapped all the time), kmap is turned into a page_address call.
+
+	 * The issue is that with use of the page_address + virt_to_page
+	 * sequence the top byte value of the original pointer gets lost (gets
+	 * set to KASAN_TAG_KERNEL (0xFF)).
+	 */
+	if (tag == KASAN_TAG_KERNEL)
+		return;
+
+	untagged_addr = reset_tag((const void *)addr);
+	if (unlikely(untagged_addr <
+			kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
+		kasan_report(addr, size, write, ret_ip);
+		return;
+	}
+	shadow_first = kasan_mem_to_shadow(untagged_addr);
+	shadow_last = kasan_mem_to_shadow(untagged_addr + size - 1);
+	for (shadow = shadow_first; shadow <= shadow_last; shadow++) {
+		if (*shadow != tag) {
+			kasan_report(addr, size, write, ret_ip);
+			return;
+		}
+	}
 }
 
 #define DEFINE_HWASAN_LOAD_STORE(size)					\
 	void __hwasan_load##size##_noabort(unsigned long addr)		\
 	{								\
+		check_memory_region(addr, size, false, _RET_IP_);	\
 	}								\
 	EXPORT_SYMBOL(__hwasan_load##size##_noabort);			\
 	void __hwasan_store##size##_noabort(unsigned long addr)		\
 	{								\
+		check_memory_region(addr, size, true, _RET_IP_);	\
 	}								\
 	EXPORT_SYMBOL(__hwasan_store##size##_noabort)
 
@@ -98,15 +143,18 @@ DEFINE_HWASAN_LOAD_STORE(16);
 
 void __hwasan_loadN_noabort(unsigned long addr, unsigned long size)
 {
+	check_memory_region(addr, size, false, _RET_IP_);
 }
 EXPORT_SYMBOL(__hwasan_loadN_noabort);
 
 void __hwasan_storeN_noabort(unsigned long addr, unsigned long size)
 {
+	check_memory_region(addr, size, true, _RET_IP_);
 }
 EXPORT_SYMBOL(__hwasan_storeN_noabort);
 
 void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size)
 {
+	kasan_poison_shadow((void *)addr, size, tag);
 }
 EXPORT_SYMBOL(__hwasan_tag_memory);
-- 
2.20.0.rc1.387.gf8505762e3-goog


_______________________________________________
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v13 20/25] kasan, arm64: add brk handler for inline instrumentation

[Andrey Konovalov]

Tag-based KASAN inline instrumentation mode (which embeds checks of shadow
memory into the generated code, instead of inserting a callback) generates
a brk instruction when a tag mismatch is detected.

This commit adds a tag-based KASAN specific brk handler, that decodes the
immediate value passed to the brk instructions (to extract information
about the memory access that triggered the mismatch), reads the register
values (x0 contains the guilty address) and reports the bug.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/brk-imm.h |  2 ++
 arch/arm64/kernel/traps.c        | 60 ++++++++++++++++++++++++++++++++
 include/linux/kasan.h            |  3 ++
 3 files changed, 65 insertions(+)

diff --git a/arch/arm64/include/asm/brk-imm.h b/arch/arm64/include/asm/brk-imm.h
index ed693c5bcec0..2945fe6cd863 100644
--- a/arch/arm64/include/asm/brk-imm.h
+++ b/arch/arm64/include/asm/brk-imm.h
@@ -16,10 +16,12 @@
  * 0x400: for dynamic BRK instruction
  * 0x401: for compile time BRK instruction
  * 0x800: kernel-mode BUG() and WARN() traps
+ * 0x9xx: tag-based KASAN trap (allowed values 0x900 - 0x9ff)
  */
 #define FAULT_BRK_IMM			0x100
 #define KGDB_DYN_DBG_BRK_IMM		0x400
 #define KGDB_COMPILED_DBG_BRK_IMM	0x401
 #define BUG_BRK_IMM			0x800
+#define KASAN_BRK_IMM			0x900
 
 #endif
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 5f4d9acb32f5..cdc71cf70aad 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -35,6 +35,7 @@
 #include <linux/sizes.h>
 #include <linux/syscalls.h>
 #include <linux/mm_types.h>
+#include <linux/kasan.h>
 
 #include <asm/atomic.h>
 #include <asm/bug.h>
@@ -969,6 +970,58 @@ static struct break_hook bug_break_hook = {
 	.fn = bug_handler,
 };
 
+#ifdef CONFIG_KASAN_SW_TAGS
+
+#define KASAN_ESR_RECOVER	0x20
+#define KASAN_ESR_WRITE	0x10
+#define KASAN_ESR_SIZE_MASK	0x0f
+#define KASAN_ESR_SIZE(esr)	(1 << ((esr) & KASAN_ESR_SIZE_MASK))
+
+static int kasan_handler(struct pt_regs *regs, unsigned int esr)
+{
+	bool recover = esr & KASAN_ESR_RECOVER;
+	bool write = esr & KASAN_ESR_WRITE;
+	size_t size = KASAN_ESR_SIZE(esr);
+	u64 addr = regs->regs[0];
+	u64 pc = regs->pc;
+
+	if (user_mode(regs))
+		return DBG_HOOK_ERROR;
+
+	kasan_report(addr, size, write, pc);
+
+	/*
+	 * The instrumentation allows to control whether we can proceed after
+	 * a crash was detected. This is done by passing the -recover flag to
+	 * the compiler. Disabling recovery allows to generate more compact
+	 * code.
+	 *
+	 * Unfortunately disabling recovery doesn't work for the kernel right
+	 * now. KASAN reporting is disabled in some contexts (for example when
+	 * the allocator accesses slab object metadata; this is controlled by
+	 * current->kasan_depth). All these accesses are detected by the tool,
+	 * even though the reports for them are not printed.
+	 *
+	 * This is something that might be fixed at some point in the future.
+	 */
+	if (!recover)
+		die("Oops - KASAN", regs, 0);
+
+	/* If thread survives, skip over the brk instruction and continue: */
+	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
+	return DBG_HOOK_HANDLED;
+}
+
+#define KASAN_ESR_VAL (0xf2000000 | KASAN_BRK_IMM)
+#define KASAN_ESR_MASK 0xffffff00
+
+static struct break_hook kasan_break_hook = {
+	.esr_val = KASAN_ESR_VAL,
+	.esr_mask = KASAN_ESR_MASK,
+	.fn = kasan_handler,
+};
+#endif
+
 /*
  * Initial handler for AArch64 BRK exceptions
  * This handler only used until debug_traps_init().
@@ -976,6 +1029,10 @@ static struct break_hook bug_break_hook = {
 int __init early_brk64(unsigned long addr, unsigned int esr,
 		struct pt_regs *regs)
 {
+#ifdef CONFIG_KASAN_SW_TAGS
+	if ((esr & KASAN_ESR_MASK) == KASAN_ESR_VAL)
+		return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
+#endif
 	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
 }
 
@@ -983,4 +1040,7 @@ int __init early_brk64(unsigned long addr, unsigned int esr,
 void __init trap_init(void)
 {
 	register_break_hook(&bug_break_hook);
+#ifdef CONFIG_KASAN_SW_TAGS
+	register_break_hook(&kasan_break_hook);
+#endif
 }
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index a477ce2abdc9..8da7b7a4397a 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -173,6 +173,9 @@ void kasan_init_tags(void);
 
 void *kasan_reset_tag(const void *addr);
 
+void kasan_report(unsigned long addr, size_t size,
+		bool is_write, unsigned long ip);
+
 #else /* CONFIG_KASAN_SW_TAGS */
 
 static inline void kasan_init_tags(void) { }
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 21/25] kasan, mm, arm64: tag non slab memory allocated via pagealloc

[Andrey Konovalov]

Tag-based KASAN doesn't check memory accesses through pointers tagged with
0xff. When page_address is used to get pointer to memory that corresponds
to some page, the tag of the resulting pointer gets set to 0xff, even
though the allocated memory might have been tagged differently.

For slab pages it's impossible to recover the correct tag to return from
page_address, since the page might contain multiple slab objects tagged
with different values, and we can't know in advance which one of them is
going to get accessed. For non slab pages however, we can recover the tag
in page_address, since the whole page was marked with the same tag.

This patch adds tagging to non slab memory allocated with pagealloc. To
set the tag of the pointer returned from page_address, the tag gets stored
to page->flags when the memory gets allocated.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/memory.h   |  8 +++++++-
 include/linux/mm.h                | 29 +++++++++++++++++++++++++++++
 include/linux/page-flags-layout.h | 10 ++++++++++
 mm/cma.c                          | 11 +++++++++++
 mm/kasan/common.c                 | 15 +++++++++++++--
 mm/page_alloc.c                   |  1 +
 mm/slab.c                         |  2 +-
 7 files changed, 72 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 5fe2353f111b..7db28404609b 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -314,7 +314,13 @@ static inline void *phys_to_virt(phys_addr_t x)
 #define __virt_to_pgoff(kaddr)	(((u64)(kaddr) & ~PAGE_OFFSET) / PAGE_SIZE * sizeof(struct page))
 #define __page_to_voff(kaddr)	(((u64)(kaddr) & ~VMEMMAP_START) * PAGE_SIZE / sizeof(struct page))
 
-#define page_to_virt(page)	((void *)((__page_to_voff(page)) | PAGE_OFFSET))
+#define page_to_virt(page)	({					\
+	unsigned long __addr =						\
+		((__page_to_voff(page)) | PAGE_OFFSET);			\
+	__addr = __tag_set(__addr, page_kasan_tag(page));		\
+	((void *)__addr);						\
+})
+
 #define virt_to_page(vaddr)	((struct page *)((__virt_to_pgoff(vaddr)) | VMEMMAP_START))
 
 #define _virt_addr_valid(kaddr)	pfn_valid((((u64)(kaddr) & ~PAGE_OFFSET) \
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5411de93a363..b4d01969e700 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -804,6 +804,7 @@ vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf);
 #define NODES_PGOFF		(SECTIONS_PGOFF - NODES_WIDTH)
 #define ZONES_PGOFF		(NODES_PGOFF - ZONES_WIDTH)
 #define LAST_CPUPID_PGOFF	(ZONES_PGOFF - LAST_CPUPID_WIDTH)
+#define KASAN_TAG_PGOFF		(LAST_CPUPID_PGOFF - KASAN_TAG_WIDTH)
 
 /*
  * Define the bit shifts to access each section.  For non-existent
@@ -814,6 +815,7 @@ vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf);
 #define NODES_PGSHIFT		(NODES_PGOFF * (NODES_WIDTH != 0))
 #define ZONES_PGSHIFT		(ZONES_PGOFF * (ZONES_WIDTH != 0))
 #define LAST_CPUPID_PGSHIFT	(LAST_CPUPID_PGOFF * (LAST_CPUPID_WIDTH != 0))
+#define KASAN_TAG_PGSHIFT	(KASAN_TAG_PGOFF * (KASAN_TAG_WIDTH != 0))
 
 /* NODE:ZONE or SECTION:ZONE is used to ID a zone for the buddy allocator */
 #ifdef NODE_NOT_IN_PAGE_FLAGS
@@ -836,6 +838,7 @@ vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf);
 #define NODES_MASK		((1UL << NODES_WIDTH) - 1)
 #define SECTIONS_MASK		((1UL << SECTIONS_WIDTH) - 1)
 #define LAST_CPUPID_MASK	((1UL << LAST_CPUPID_SHIFT) - 1)
+#define KASAN_TAG_MASK		((1UL << KASAN_TAG_WIDTH) - 1)
 #define ZONEID_MASK		((1UL << ZONEID_SHIFT) - 1)
 
 static inline enum zone_type page_zonenum(const struct page *page)
@@ -1101,6 +1104,32 @@ static inline bool cpupid_match_pid(struct task_struct *task, int cpupid)
 }
 #endif /* CONFIG_NUMA_BALANCING */
 
+#ifdef CONFIG_KASAN_SW_TAGS
+static inline u8 page_kasan_tag(const struct page *page)
+{
+	return (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK;
+}
+
+static inline void page_kasan_tag_set(struct page *page, u8 tag)
+{
+	page->flags &= ~(KASAN_TAG_MASK << KASAN_TAG_PGSHIFT);
+	page->flags |= (tag & KASAN_TAG_MASK) << KASAN_TAG_PGSHIFT;
+}
+
+static inline void page_kasan_tag_reset(struct page *page)
+{
+	page_kasan_tag_set(page, 0xff);
+}
+#else
+static inline u8 page_kasan_tag(const struct page *page)
+{
+	return 0xff;
+}
+
+static inline void page_kasan_tag_set(struct page *page, u8 tag) { }
+static inline void page_kasan_tag_reset(struct page *page) { }
+#endif
+
 static inline struct zone *page_zone(const struct page *page)
 {
 	return &NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)];
diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
index 7ec86bf31ce4..1dda31825ec4 100644
--- a/include/linux/page-flags-layout.h
+++ b/include/linux/page-flags-layout.h
@@ -82,6 +82,16 @@
 #define LAST_CPUPID_WIDTH 0
 #endif
 
+#ifdef CONFIG_KASAN_SW_TAGS
+#define KASAN_TAG_WIDTH 8
+#if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \
+	> BITS_PER_LONG - NR_PAGEFLAGS
+#error "KASAN: not enough bits in page flags for tag"
+#endif
+#else
+#define KASAN_TAG_WIDTH 0
+#endif
+
 /*
  * We are going to use the flags for the page to node mapping if its in
  * there.  This includes the case where there is no node, so it is implicit.
diff --git a/mm/cma.c b/mm/cma.c
index 4cb76121a3ab..c7b39dd3b4f6 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -407,6 +407,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 	unsigned long pfn = -1;
 	unsigned long start = 0;
 	unsigned long bitmap_maxno, bitmap_no, bitmap_count;
+	size_t i;
 	struct page *page = NULL;
 	int ret = -ENOMEM;
 
@@ -466,6 +467,16 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 
 	trace_cma_alloc(pfn, page, count, align);
 
+	/*
+	 * CMA can allocate multiple page blocks, which results in different
+	 * blocks being marked with different tags. Reset the tags to ignore
+	 * those page blocks.
+	 */
+	if (page) {
+		for (i = 0; i < count; i++)
+			page_kasan_tag_reset(page + i);
+	}
+
 	if (ret && !no_warn) {
 		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
 			__func__, count, ret);
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 27f0cae336c9..195ca385cf7a 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -220,8 +220,15 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
 
 void kasan_alloc_pages(struct page *page, unsigned int order)
 {
+	u8 tag;
+	unsigned long i;
+
 	if (unlikely(PageHighMem(page)))
 		return;
+
+	tag = random_tag();
+	for (i = 0; i < (1 << order); i++)
+		page_kasan_tag_set(page + i, tag);
 	kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 }
 
@@ -319,6 +326,10 @@ struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 
 void kasan_poison_slab(struct page *page)
 {
+	unsigned long i;
+
+	for (i = 0; i < (1 << compound_order(page)); i++)
+		page_kasan_tag_reset(page + i);
 	kasan_poison_shadow(page_address(page),
 			PAGE_SIZE << compound_order(page),
 			KASAN_KMALLOC_REDZONE);
@@ -517,7 +528,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip)
 	page = virt_to_head_page(ptr);
 
 	if (unlikely(!PageSlab(page))) {
-		if (reset_tag(ptr) != page_address(page)) {
+		if (ptr != page_address(page)) {
 			kasan_report_invalid_free(ptr, ip);
 			return;
 		}
@@ -530,7 +541,7 @@ void kasan_poison_kfree(void *ptr, unsigned long ip)
 
 void kasan_kfree_large(void *ptr, unsigned long ip)
 {
-	if (reset_tag(ptr) != page_address(virt_to_head_page(ptr)))
+	if (ptr != page_address(virt_to_head_page(ptr)))
 		kasan_report_invalid_free(ptr, ip);
 	/* The object will be poisoned by page_alloc. */
 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ec9cc407216..365dc0930f8c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1183,6 +1183,7 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	init_page_count(page);
 	page_mapcount_reset(page);
 	page_cpupid_reset_last(page);
+	page_kasan_tag_reset(page);
 
 	INIT_LIST_HEAD(&page->lru);
 #ifdef WANT_PAGE_VIRTUAL
diff --git a/mm/slab.c b/mm/slab.c
index d2f827316dfc..d747433ecdbb 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2357,7 +2357,7 @@ static void *alloc_slabmgmt(struct kmem_cache *cachep,
 	void *freelist;
 	void *addr = page_address(page);
 
-	page->s_mem = addr + colour_off;
+	page->s_mem = kasan_reset_tag(addr) + colour_off;
 	page->active = 0;
 
 	if (OBJFREELIST_SLAB(cachep))
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 22/25] kasan: add __must_check annotations to kasan hooks

[Andrey Konovalov]

This patch adds __must_check annotations to kasan hooks that return a
pointer to make sure that a tagged pointer always gets propagated.

Suggested-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/kasan.h | 16 ++++++++++------
 mm/kasan/common.c     | 15 +++++++++------
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 8da7b7a4397a..b40ea104dd36 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -49,16 +49,20 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 void kasan_poison_slab(struct page *page);
 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
 void kasan_poison_object_data(struct kmem_cache *cache, void *object);
-void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object);
+void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
+					const void *object);
 
-void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags);
+void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
+						gfp_t flags);
 void kasan_kfree_large(void *ptr, unsigned long ip);
 void kasan_poison_kfree(void *ptr, unsigned long ip);
-void *kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size,
-		  gfp_t flags);
-void *kasan_krealloc(const void *object, size_t new_size, gfp_t flags);
+void * __must_check kasan_kmalloc(struct kmem_cache *s, const void *object,
+					size_t size, gfp_t flags);
+void * __must_check kasan_krealloc(const void *object, size_t new_size,
+					gfp_t flags);
 
-void *kasan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags);
+void * __must_check kasan_slab_alloc(struct kmem_cache *s, void *object,
+					gfp_t flags);
 bool kasan_slab_free(struct kmem_cache *s, void *object, unsigned long ip);
 
 struct kasan_cache {
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 195ca385cf7a..1144e741feb6 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -373,7 +373,8 @@ static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new)
 #endif
 }
 
-void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
+void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
+						const void *object)
 {
 	struct kasan_alloc_meta *alloc_info;
 
@@ -389,7 +390,8 @@ void *kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 	return (void *)object;
 }
 
-void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
+void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
+					gfp_t flags)
 {
 	return kasan_kmalloc(cache, object, cache->object_size, flags);
 }
@@ -449,8 +451,8 @@ bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 	return __kasan_slab_free(cache, object, ip, true);
 }
 
-void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
-		   gfp_t flags)
+void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
+					size_t size, gfp_t flags)
 {
 	unsigned long redzone_start;
 	unsigned long redzone_end;
@@ -482,7 +484,8 @@ void *kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
 }
 EXPORT_SYMBOL(kasan_kmalloc);
 
-void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
+void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
+						gfp_t flags)
 {
 	struct page *page;
 	unsigned long redzone_start;
@@ -506,7 +509,7 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 	return (void *)ptr;
 }
 
-void *kasan_krealloc(const void *object, size_t size, gfp_t flags)
+void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
 {
 	struct page *page;
 
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 23/25] kasan, arm64: select HAVE_ARCH_KASAN_SW_TAGS

[Andrey Konovalov]

Now, that all the necessary infrastructure code has been introduced,
select HAVE_ARCH_KASAN_SW_TAGS for arm64 to enable software tag-based
KASAN mode.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ea2ab0330e3a..66f2c625fd1c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -111,6 +111,7 @@ config ARM64
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
 	select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
+	select HAVE_ARCH_KASAN_SW_TAGS if HAVE_ARCH_KASAN
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
-- 
2.20.0.rc1.387.gf8505762e3-goog


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[PATCH v13 24/25] kasan: update documentation

[Andrey Konovalov]

This patch updates KASAN documentation to reflect the addition of the new
tag-based mode.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 Documentation/dev-tools/kasan.rst | 232 ++++++++++++++++++------------
 1 file changed, 138 insertions(+), 94 deletions(-)

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index aabc8738b3d8..8e956e0588fc 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -4,15 +4,25 @@ The Kernel Address Sanitizer (KASAN)
 Overview
 --------
 
-KernelAddressSANitizer (KASAN) is a dynamic memory error detector. It provides
-a fast and comprehensive solution for finding use-after-free and out-of-bounds
-bugs.
+KernelAddressSANitizer (KASAN) is a dynamic memory error detector designed to
+find out-of-bound and use-after-free bugs. KASAN has two modes: generic KASAN
+(similar to userspace ASan) and software tag-based KASAN (similar to userspace
+HWASan).
 
-KASAN uses compile-time instrumentation for checking every memory access,
-therefore you will need a GCC version 4.9.2 or later. GCC 5.0 or later is
-required for detection of out-of-bounds accesses to stack or global variables.
+KASAN uses compile-time instrumentation to insert validity checks before every
+memory access, and therefore requires a compiler version that supports that.
 
-Currently KASAN is supported only for the x86_64 and arm64 architectures.
+Generic KASAN is supported in both GCC and Clang. With GCC it requires version
+4.9.2 or later for basic support and version 5.0 or later for detection of
+out-of-bounds accesses for stack and global variables and for inline
+instrumentation mode (see the Usage section). With Clang it requires version
+7.0.0 or later and it doesn't support detection of out-of-bounds accesses for
+global variables yet.
+
+Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
+
+Currently generic KASAN is supported for the x86_64, arm64, xtensa and s390
+architectures, and tag-based KASAN is supported only for arm64.
 
 Usage
 -----
@@ -21,12 +31,14 @@ To enable KASAN configure kernel with::
 
 	  CONFIG_KASAN = y
 
-and choose between CONFIG_KASAN_OUTLINE and CONFIG_KASAN_INLINE. Outline and
-inline are compiler instrumentation types. The former produces smaller binary
-the latter is 1.1 - 2 times faster. Inline instrumentation requires a GCC
-version 5.0 or later.
+and choose between CONFIG_KASAN_GENERIC (to enable generic KASAN) and
+CONFIG_KASAN_SW_TAGS (to enable software tag-based KASAN).
 
-KASAN works with both SLUB and SLAB memory allocators.
+You also need to choose between CONFIG_KASAN_OUTLINE and CONFIG_KASAN_INLINE.
+Outline and inline are compiler instrumentation types. The former produces
+smaller binary while the latter is 1.1 - 2 times faster.
+
+Both KASAN modes work with both SLUB and SLAB memory allocators.
 For better bug detection and nicer reporting, enable CONFIG_STACKTRACE.
 
 To disable instrumentation for specific files or directories, add a line
@@ -43,85 +55,85 @@ similar to the following to the respective kernel Makefile:
 Error reports
 ~~~~~~~~~~~~~
 
-A typical out of bounds access report looks like this::
+A typical out-of-bounds access generic KASAN report looks like this::
 
     ==================================================================
-    BUG: AddressSanitizer: out of bounds access in kmalloc_oob_right+0x65/0x75 [test_kasan] at addr ffff8800693bc5d3
-    Write of size 1 by task modprobe/1689
-    =============================================================================
-    BUG kmalloc-128 (Not tainted): kasan error
-    -----------------------------------------------------------------------------
-
-    Disabling lock debugging due to kernel taint
-    INFO: Allocated in kmalloc_oob_right+0x3d/0x75 [test_kasan] age=0 cpu=0 pid=1689
-     __slab_alloc+0x4b4/0x4f0
-     kmem_cache_alloc_trace+0x10b/0x190
-     kmalloc_oob_right+0x3d/0x75 [test_kasan]
-     init_module+0x9/0x47 [test_kasan]
-     do_one_initcall+0x99/0x200
-     load_module+0x2cb3/0x3b20
-     SyS_finit_module+0x76/0x80
-     system_call_fastpath+0x12/0x17
-    INFO: Slab 0xffffea0001a4ef00 objects=17 used=7 fp=0xffff8800693bd728 flags=0x100000000004080
-    INFO: Object 0xffff8800693bc558 @offset=1368 fp=0xffff8800693bc720
-
-    Bytes b4 ffff8800693bc548: 00 00 00 00 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a  ........ZZZZZZZZ
-    Object ffff8800693bc558: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc568: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc578: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc588: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc598: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc5a8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc5b8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
-    Object ffff8800693bc5c8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5  kkkkkkkkkkkkkkk.
-    Redzone ffff8800693bc5d8: cc cc cc cc cc cc cc cc                          ........
-    Padding ffff8800693bc718: 5a 5a 5a 5a 5a 5a 5a 5a                          ZZZZZZZZ
-    CPU: 0 PID: 1689 Comm: modprobe Tainted: G    B          3.18.0-rc1-mm1+ #98
-    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
-     ffff8800693bc000 0000000000000000 ffff8800693bc558 ffff88006923bb78
-     ffffffff81cc68ae 00000000000000f3 ffff88006d407600 ffff88006923bba8
-     ffffffff811fd848 ffff88006d407600 ffffea0001a4ef00 ffff8800693bc558
+    BUG: KASAN: slab-out-of-bounds in kmalloc_oob_right+0xa8/0xbc [test_kasan]
+    Write of size 1 at addr ffff8801f44ec37b by task insmod/2760
+    
+    CPU: 1 PID: 2760 Comm: insmod Not tainted 4.19.0-rc3+ #698
+    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
     Call Trace:
-     [<ffffffff81cc68ae>] dump_stack+0x46/0x58
-     [<ffffffff811fd848>] print_trailer+0xf8/0x160
-     [<ffffffffa00026a7>] ? kmem_cache_oob+0xc3/0xc3 [test_kasan]
-     [<ffffffff811ff0f5>] object_err+0x35/0x40
-     [<ffffffffa0002065>] ? kmalloc_oob_right+0x65/0x75 [test_kasan]
-     [<ffffffff8120b9fa>] kasan_report_error+0x38a/0x3f0
-     [<ffffffff8120a79f>] ? kasan_poison_shadow+0x2f/0x40
-     [<ffffffff8120b344>] ? kasan_unpoison_shadow+0x14/0x40
-     [<ffffffff8120a79f>] ? kasan_poison_shadow+0x2f/0x40
-     [<ffffffffa00026a7>] ? kmem_cache_oob+0xc3/0xc3 [test_kasan]
-     [<ffffffff8120a995>] __asan_store1+0x75/0xb0
-     [<ffffffffa0002601>] ? kmem_cache_oob+0x1d/0xc3 [test_kasan]
-     [<ffffffffa0002065>] ? kmalloc_oob_right+0x65/0x75 [test_kasan]
-     [<ffffffffa0002065>] kmalloc_oob_right+0x65/0x75 [test_kasan]
-     [<ffffffffa00026b0>] init_module+0x9/0x47 [test_kasan]
-     [<ffffffff810002d9>] do_one_initcall+0x99/0x200
-     [<ffffffff811e4e5c>] ? __vunmap+0xec/0x160
-     [<ffffffff81114f63>] load_module+0x2cb3/0x3b20
-     [<ffffffff8110fd70>] ? m_show+0x240/0x240
-     [<ffffffff81115f06>] SyS_finit_module+0x76/0x80
-     [<ffffffff81cd3129>] system_call_fastpath+0x12/0x17
+     dump_stack+0x94/0xd8
+     print_address_description+0x73/0x280
+     kasan_report+0x144/0x187
+     __asan_report_store1_noabort+0x17/0x20
+     kmalloc_oob_right+0xa8/0xbc [test_kasan]
+     kmalloc_tests_init+0x16/0x700 [test_kasan]
+     do_one_initcall+0xa5/0x3ae
+     do_init_module+0x1b6/0x547
+     load_module+0x75df/0x8070
+     __do_sys_init_module+0x1c6/0x200
+     __x64_sys_init_module+0x6e/0xb0
+     do_syscall_64+0x9f/0x2c0
+     entry_SYSCALL_64_after_hwframe+0x44/0xa9
+    RIP: 0033:0x7f96443109da
+    RSP: 002b:00007ffcf0b51b08 EFLAGS: 00000202 ORIG_RAX: 00000000000000af
+    RAX: ffffffffffffffda RBX: 000055dc3ee521a0 RCX: 00007f96443109da
+    RDX: 00007f96445cff88 RSI: 0000000000057a50 RDI: 00007f9644992000
+    RBP: 000055dc3ee510b0 R08: 0000000000000003 R09: 0000000000000000
+    R10: 00007f964430cd0a R11: 0000000000000202 R12: 00007f96445cff88
+    R13: 000055dc3ee51090 R14: 0000000000000000 R15: 0000000000000000
+    
+    Allocated by task 2760:
+     save_stack+0x43/0xd0
+     kasan_kmalloc+0xa7/0xd0
+     kmem_cache_alloc_trace+0xe1/0x1b0
+     kmalloc_oob_right+0x56/0xbc [test_kasan]
+     kmalloc_tests_init+0x16/0x700 [test_kasan]
+     do_one_initcall+0xa5/0x3ae
+     do_init_module+0x1b6/0x547
+     load_module+0x75df/0x8070
+     __do_sys_init_module+0x1c6/0x200
+     __x64_sys_init_module+0x6e/0xb0
+     do_syscall_64+0x9f/0x2c0
+     entry_SYSCALL_64_after_hwframe+0x44/0xa9
+    
+    Freed by task 815:
+     save_stack+0x43/0xd0
+     __kasan_slab_free+0x135/0x190
+     kasan_slab_free+0xe/0x10
+     kfree+0x93/0x1a0
+     umh_complete+0x6a/0xa0
+     call_usermodehelper_exec_async+0x4c3/0x640
+     ret_from_fork+0x35/0x40
+    
+    The buggy address belongs to the object at ffff8801f44ec300
+     which belongs to the cache kmalloc-128 of size 128
+    The buggy address is located 123 bytes inside of
+     128-byte region [ffff8801f44ec300, ffff8801f44ec380)
+    The buggy address belongs to the page:
+    page:ffffea0007d13b00 count:1 mapcount:0 mapping:ffff8801f7001640 index:0x0
+    flags: 0x200000000000100(slab)
+    raw: 0200000000000100 ffffea0007d11dc0 0000001a0000001a ffff8801f7001640
+    raw: 0000000000000000 0000000080150015 00000001ffffffff 0000000000000000
+    page dumped because: kasan: bad access detected
+    
     Memory state around the buggy address:
-     ffff8800693bc300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
-     ffff8800693bc380: fc fc 00 00 00 00 00 00 00 00 00 00 00 00 00 fc
-     ffff8800693bc400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
-     ffff8800693bc480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
-     ffff8800693bc500: fc fc fc fc fc fc fc fc fc fc fc 00 00 00 00 00
-    >ffff8800693bc580: 00 00 00 00 00 00 00 00 00 00 03 fc fc fc fc fc
-                                                 ^
-     ffff8800693bc600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
-     ffff8800693bc680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
-     ffff8800693bc700: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
-     ffff8800693bc780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
-     ffff8800693bc800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
+     ffff8801f44ec200: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
+     ffff8801f44ec280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
+    >ffff8801f44ec300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03
+                                                                    ^
+     ffff8801f44ec380: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
+     ffff8801f44ec400: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
     ==================================================================
 
-The header of the report discribe what kind of bug happened and what kind of
-access caused it. It's followed by the description of the accessed slub object
-(see 'SLUB Debug output' section in Documentation/vm/slub.rst for details) and
-the description of the accessed memory page.
+The header of the report provides a short summary of what kind of bug happened
+and what kind of access caused it. It's followed by a stack trace of the bad
+access, a stack trace of where the accessed memory was allocated (in case bad
+access happens on a slab object), and a stack trace of where the object was
+freed (in case of a use-after-free bug report). Next comes a description of
+the accessed slab object and information about the accessed memory page.
 
 In the last section the report shows memory state around the accessed address.
 Reading this part requires some understanding of how KASAN works.
@@ -138,18 +150,24 @@ inaccessible memory like redzones or freed memory (see mm/kasan/kasan.h).
 In the report above the arrows point to the shadow byte 03, which means that
 the accessed address is partially accessible.
 
+For tag-based KASAN this last report section shows the memory tags around the
+accessed address (see Implementation details section).
+
 
 Implementation details
 ----------------------
 
+Generic KASAN
+~~~~~~~~~~~~~
+
 From a high level, our approach to memory error detection is similar to that
 of kmemcheck: use shadow memory to record whether each byte of memory is safe
-to access, and use compile-time instrumentation to check shadow memory on each
-memory access.
+to access, and use compile-time instrumentation to insert checks of shadow
+memory on each memory access.
 
-AddressSanitizer dedicates 1/8 of kernel memory to its shadow memory
-(e.g. 16TB to cover 128TB on x86_64) and uses direct mapping with a scale and
-offset to translate a memory address to its corresponding shadow address.
+Generic KASAN dedicates 1/8th of kernel memory to its shadow memory (e.g. 16TB
+to cover 128TB on x86_64) and uses direct mapping with a scale and offset to
+translate a memory address to its corresponding shadow address.
 
 Here is the function which translates an address to its corresponding shadow
 address::
@@ -162,12 +180,38 @@ address::
 
 where ``KASAN_SHADOW_SCALE_SHIFT = 3``.
 
-Compile-time instrumentation used for checking memory accesses. Compiler inserts
-function calls (__asan_load*(addr), __asan_store*(addr)) before each memory
-access of size 1, 2, 4, 8 or 16. These functions check whether memory access is
-valid or not by checking corresponding shadow memory.
+Compile-time instrumentation is used to insert memory access checks. Compiler
+inserts function calls (__asan_load*(addr), __asan_store*(addr)) before each
+memory access of size 1, 2, 4, 8 or 16. These functions check whether memory
+access is valid or not by checking corresponding shadow memory.
 
 GCC 5.0 has possibility to perform inline instrumentation. Instead of making
 function calls GCC directly inserts the code to check the shadow memory.
 This option significantly enlarges kernel but it gives x1.1-x2 performance
 boost over outline instrumented kernel.
+
+Software tag-based KASAN
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Tag-based KASAN uses the Top Byte Ignore (TBI) feature of modern arm64 CPUs to
+store a pointer tag in the top byte of kernel pointers. Like generic KASAN it
+uses shadow memory to store memory tags associated with each 16-byte memory
+cell (therefore it dedicates 1/16th of the kernel memory for shadow memory).
+
+On each memory allocation tag-based KASAN generates a random tag, tags the
+allocated memory with this tag, and embeds this tag into the returned pointer.
+Software tag-based KASAN uses compile-time instrumentation to insert checks
+before each memory access. These checks make sure that tag of the memory that
+is being accessed is equal to tag of the pointer that is used to access this
+memory. In case of a tag mismatch tag-based KASAN prints a bug report.
+
+Software tag-based KASAN also has two instrumentation modes (outline, that
+emits callbacks to check memory accesses; and inline, that performs the shadow
+memory checks inline). With outline instrumentation mode, a bug report is
+simply printed from the function that performs the access check. With inline
+instrumentation a brk instruction is emitted by the compiler, and a dedicated
+brk handler is used to print bug reports.
+
+A potential expansion of this mode is a hardware tag-based mode, which would
+use hardware memory tagging support instead of compiler instrumentation and
+manual shadow memory manipulation.
-- 
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[PATCH v13 25/25] kasan: add SPDX-License-Identifier mark to source files

[Andrey Konovalov]

This patch adds a "SPDX-License-Identifier: GPL-2.0" mark to all source
files under mm/kasan.

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/common.c         | 1 +
 mm/kasan/generic.c        | 1 +
 mm/kasan/generic_report.c | 1 +
 mm/kasan/init.c           | 1 +
 mm/kasan/quarantine.c     | 1 +
 mm/kasan/report.c         | 1 +
 mm/kasan/tags.c           | 1 +
 mm/kasan/tags_report.c    | 1 +
 8 files changed, 8 insertions(+)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 1144e741feb6..03d5d1374ca7 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains common generic and tag-based KASAN code.
  *
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index b8de6d33c55c..ccb6207276e3 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains core generic KASAN code.
  *
diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c
index a4604cceae59..5e12035888f2 100644
--- a/mm/kasan/generic_report.c
+++ b/mm/kasan/generic_report.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains generic KASAN specific error reporting code.
  *
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index 2b21d3717d62..34afad56497b 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains some kasan initialization code.
  *
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index b209dbaefde8..57334ef2d7ef 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * KASAN quarantine.
  *
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 214d85035f99..ca9418fe9232 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains common generic and tag-based KASAN error reporting code.
  *
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
index 1d1b79350e28..0777649e07c4 100644
--- a/mm/kasan/tags.c
+++ b/mm/kasan/tags.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains core tag-based KASAN code.
  *
diff --git a/mm/kasan/tags_report.c b/mm/kasan/tags_report.c
index 573c51d20d09..8eaf5f722271 100644
--- a/mm/kasan/tags_report.c
+++ b/mm/kasan/tags_report.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * This file contains tag-based KASAN specific error reporting code.
  *
-- 
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Re: [PATCH v13 08/25] kasan: initialize shadow to 0xff for tag-based mode

[Andrey Konovalov]

On Mon, Dec 10, 2018 at 2:35 AM Paul Gortmaker
<paul.gortmaker@windriver.com> wrote:
>
> On Thu, Dec 6, 2018 at 7:25 AM Andrey Konovalov <andreyknvl@google.com> wrote:
>>
>> A tag-based KASAN shadow memory cell contains a memory tag, that
>> corresponds to the tag in the top byte of the pointer, that points to that
>> memory. The native top byte value of kernel pointers is 0xff, so with
>> tag-based KASAN we need to initialize shadow memory to 0xff.
>>
>> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
>> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>> ---
>>  arch/arm64/mm/kasan_init.c | 15 +++++++++++++--
>>  include/linux/kasan.h      |  8 ++++++++
>
>
> The version of this in  linux-next breaks arm64 allmodconfig for me:
>
> mm/kasan/common.c: In function ‘kasan_module_alloc’:
> mm/kasan/common.c:481:17: error: ‘KASAN_SHADOW_INIT’ undeclared (first use in this function)
>    __memset(ret, KASAN_SHADOW_INIT, shadow_size);
>                  ^
> mm/kasan/common.c:481:17: note: each undeclared identifier is reported only once for each function it appears in
> make[3]: *** [mm/kasan/common.o] Error 1
> make[3]: *** Waiting for unfinished jobs....
> make[2]: *** [mm/kasan] Error 2
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [mm/] Error 2
> make: *** [sub-make] Error 2

Hi Paul,

This is my bad, this should be fixed in v13 of this patchset, which is
in mm right now but not in linux-next yet as it seems.

Thanks!

>
> An automated git bisect-run points at this:
>
> 5c36287813721999e79ac76f637f1ba7e5054402 is the first bad commit
> commit 5c36287813721999e79ac76f637f1ba7e5054402
> Author: Andrey Konovalov <andreyknvl@google.com>
> Date:   Wed Dec 5 11:13:21 2018 +1100
>
>     kasan: initialize shadow to 0xff for tag-based mode
>
> A quick look at the commit makes me think that the case where the
> "# CONFIG_KASAN_GENERIC is not set" has not been handled.
>
> I'm using an older gcc 4.8.3 - only used for build testing.
>
> Paul.
> --
>
>>  mm/kasan/common.c          |  3 ++-
>>  3 files changed, 23 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
>> index 4ebc19422931..7a4a0904cac8 100644
>> --- a/arch/arm64/mm/kasan_init.c
>> +++ b/arch/arm64/mm/kasan_init.c
>> @@ -43,6 +43,15 @@ static phys_addr_t __init kasan_alloc_zeroed_page(int node)
>>         return __pa(p);
>>  }
>>
>> +static phys_addr_t __init kasan_alloc_raw_page(int node)
>> +{
>> +       void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
>> +                                               __pa(MAX_DMA_ADDRESS),
>> +                                               MEMBLOCK_ALLOC_ACCESSIBLE,
>> +                                               node);
>> +       return __pa(p);
>> +}
>> +
>>  static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
>>                                       bool early)
>>  {
>> @@ -92,7 +101,9 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
>>         do {
>>                 phys_addr_t page_phys = early ?
>>                                 __pa_symbol(kasan_early_shadow_page)
>> -                                       : kasan_alloc_zeroed_page(node);
>> +                                       : kasan_alloc_raw_page(node);
>> +               if (!early)
>> +                       memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
>>                 next = addr + PAGE_SIZE;
>>                 set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
>>         } while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
>> @@ -239,7 +250,7 @@ void __init kasan_init(void)
>>                         pfn_pte(sym_to_pfn(kasan_early_shadow_page),
>>                                 PAGE_KERNEL_RO));
>>
>> -       memset(kasan_early_shadow_page, 0, PAGE_SIZE);
>> +       memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
>>         cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
>>
>>         /* At this point kasan is fully initialized. Enable error messages */
>> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
>> index ec22d548d0d7..c56af24bd3e7 100644
>> --- a/include/linux/kasan.h
>> +++ b/include/linux/kasan.h
>> @@ -153,6 +153,8 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
>>
>>  #ifdef CONFIG_KASAN_GENERIC
>>
>> +#define KASAN_SHADOW_INIT 0
>> +
>>  void kasan_cache_shrink(struct kmem_cache *cache);
>>  void kasan_cache_shutdown(struct kmem_cache *cache);
>>
>> @@ -163,4 +165,10 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
>>
>>  #endif /* CONFIG_KASAN_GENERIC */
>>
>> +#ifdef CONFIG_KASAN_SW_TAGS
>> +
>> +#define KASAN_SHADOW_INIT 0xFF
>> +
>> +#endif /* CONFIG_KASAN_SW_TAGS */
>> +
>>  #endif /* LINUX_KASAN_H */
>> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
>> index 5f68c93734ba..7134e75447ff 100644
>> --- a/mm/kasan/common.c
>> +++ b/mm/kasan/common.c
>> @@ -473,11 +473,12 @@ int kasan_module_alloc(void *addr, size_t size)
>>
>>         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
>>                         shadow_start + shadow_size,
>> -                       GFP_KERNEL | __GFP_ZERO,
>> +                       GFP_KERNEL,
>>                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
>>                         __builtin_return_address(0));
>>
>>         if (ret) {
>> +               __memset(ret, KASAN_SHADOW_INIT, shadow_size);
>>                 find_vm_area(addr)->flags |= VM_KASAN;
>>                 kmemleak_ignore(ret);
>>                 return 0;
>> --
>> 2.20.0.rc1.387.gf8505762e3-goog
>>

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Re: [PATCH v13 00/25] kasan: add software tag-based mode for arm64

[Will Deacon]

Hi Andrey,

On Thu, Dec 06, 2018 at 01:24:18PM +0100, Andrey Konovalov wrote:
> This patchset adds a new software tag-based mode to KASAN [1].
> (Initially this mode was called KHWASAN, but it got renamed,
>  see the naming rationale at the end of this section).
> 
> The plan is to implement HWASan [2] for the kernel with the incentive,
> that it's going to have comparable to KASAN performance, but in the same
> time consume much less memory, trading that off for somewhat imprecise
> bug detection and being supported only for arm64.

For the arm64 parts:

Acked-by: Will Deacon <will.deacon@arm.com>

I assume that you plan to replace the current patches in -mm with this
series?

Cheers,

Will

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Re: [PATCH v13 05/25] kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

[Luc Van Oostenryck]

On Thu, Dec 06, 2018 at 01:24:23PM +0100, Andrey Konovalov wrote:
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 3e7dafb3ea80..39f668d5066b 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -16,9 +16,13 @@
>  /* all clang versions usable with the kernel support KASAN ABI version 5 */
>  #define KASAN_ABI_VERSION 5
>  
> +#if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
>  /* emulate gcc's __SANITIZE_ADDRESS__ flag */
> -#if __has_feature(address_sanitizer)
>  #define __SANITIZE_ADDRESS__
> +#define __no_sanitize_address \
> +		__attribute__((no_sanitize("address", "hwaddress")))
> +#else
> +#define __no_sanitize_address
>  #endif
>  
>  /*
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 2010493e1040..5776da43da97 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -143,6 +143,12 @@
>  #define KASAN_ABI_VERSION 3
>  #endif
>  
> +#if __has_attribute(__no_sanitize_address__)
> +#define __no_sanitize_address __attribute__((no_sanitize_address))
> +#else
> +#define __no_sanitize_address
> +#endif

Not really important but it's the name with leading and trailing
underscores that is tested with __has_attribute() but then it's
the naked 'no_sanitize_address' that is used in the attribute.

-- Luc

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Re: [PATCH v13 00/25] kasan: add software tag-based mode for arm64

[Andrey Konovalov]

On Tue, Dec 11, 2018 at 4:18 PM Will Deacon <will.deacon@arm.com> wrote:
>
> Hi Andrey,
>
> On Thu, Dec 06, 2018 at 01:24:18PM +0100, Andrey Konovalov wrote:
> > This patchset adds a new software tag-based mode to KASAN [1].
> > (Initially this mode was called KHWASAN, but it got renamed,
> >  see the naming rationale at the end of this section).
> >
> > The plan is to implement HWASan [2] for the kernel with the incentive,
> > that it's going to have comparable to KASAN performance, but in the same
> > time consume much less memory, trading that off for somewhat imprecise
> > bug detection and being supported only for arm64.
>
> For the arm64 parts:
>
> Acked-by: Will Deacon <will.deacon@arm.com>
>
> I assume that you plan to replace the current patches in -mm with this
> series?
>
> Cheers,
>
> Will

Hi Will,

Yes, that was the intention of sending v13. Should have I sent a
separate patch with v12->v13 fixes instead? I don't know what's the
usual way to make changes to the patchset once it's in the mm tree.

Thanks!

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Re: [PATCH v13 00/25] kasan: add software tag-based mode for arm64

[Will Deacon]

[moving akpm to To:]

On Tue, Dec 11, 2018 at 04:57:27PM +0100, Andrey Konovalov wrote:
> On Tue, Dec 11, 2018 at 4:18 PM Will Deacon <will.deacon@arm.com> wrote:
> > On Thu, Dec 06, 2018 at 01:24:18PM +0100, Andrey Konovalov wrote:
> > > This patchset adds a new software tag-based mode to KASAN [1].
> > > (Initially this mode was called KHWASAN, but it got renamed,
> > >  see the naming rationale at the end of this section).
> > >
> > > The plan is to implement HWASan [2] for the kernel with the incentive,
> > > that it's going to have comparable to KASAN performance, but in the same
> > > time consume much less memory, trading that off for somewhat imprecise
> > > bug detection and being supported only for arm64.
> >
> > For the arm64 parts:
> >
> > Acked-by: Will Deacon <will.deacon@arm.com>
> >
> > I assume that you plan to replace the current patches in -mm with this
> > series?
> >
> > Cheers,
> >
> > Will
> 
> Hi Will,
> 
> Yes, that was the intention of sending v13. Should have I sent a
> separate patch with v12->v13 fixes instead? I don't know what's the
> usual way to make changes to the patchset once it's in the mm tree.

No, I was just checking that the intention was for akpm to pick this up in
preference to the old stuff! That works for me, and the minor conflict with
arm64 in next was already resolved by Stephen.

Will

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Re: [PATCH v13 05/25] kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

[Andrey Konovalov]

On Tue, Dec 11, 2018 at 4:28 PM Luc Van Oostenryck
<luc.vanoostenryck@gmail.com> wrote:
>
> On Thu, Dec 06, 2018 at 01:24:23PM +0100, Andrey Konovalov wrote:
> > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> > index 3e7dafb3ea80..39f668d5066b 100644
> > --- a/include/linux/compiler-clang.h
> > +++ b/include/linux/compiler-clang.h
> > @@ -16,9 +16,13 @@
> >  /* all clang versions usable with the kernel support KASAN ABI version 5 */
> >  #define KASAN_ABI_VERSION 5
> >
> > +#if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
> >  /* emulate gcc's __SANITIZE_ADDRESS__ flag */
> > -#if __has_feature(address_sanitizer)
> >  #define __SANITIZE_ADDRESS__
> > +#define __no_sanitize_address \
> > +             __attribute__((no_sanitize("address", "hwaddress")))
> > +#else
> > +#define __no_sanitize_address
> >  #endif
> >
> >  /*
> > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> > index 2010493e1040..5776da43da97 100644
> > --- a/include/linux/compiler-gcc.h
> > +++ b/include/linux/compiler-gcc.h
> > @@ -143,6 +143,12 @@
> >  #define KASAN_ABI_VERSION 3
> >  #endif
> >
> > +#if __has_attribute(__no_sanitize_address__)
> > +#define __no_sanitize_address __attribute__((no_sanitize_address))
> > +#else
> > +#define __no_sanitize_address
> > +#endif
>
> Not really important but it's the name with leading and trailing
> underscores that is tested with __has_attribute() but then it's
> the naked 'no_sanitize_address' that is used in the attribute.

Hi Luc,

You're right. This shouldn't be important though, since "__" in
attribute names are optional AFAIK. It might make sense to fix it as a
separate patch when this series is merged.

Thanks!

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Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Vincenzo Frascino]

Hi Andrey,

On 06/12/2018 12:24, Andrey Konovalov wrote:
> This commit adds tag-based KASAN specific hooks implementation and
> adjusts common generic and tag-based KASAN ones.
> 
> 1. When a new slab cache is created, tag-based KASAN rounds up the size of
>    the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16).
> 
> 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow
>    memory, that corresponds to this object to this tag, and embeds this
>    tag value into the top byte of the returned pointer.
> 
> 3. On each kfree tag-based KASAN poisons the shadow memory with a random
>    tag to allow detection of use-after-free bugs.
> 
> The rest of the logic of the hook implementation is very much similar to
> the one provided by generic KASAN. Tag-based KASAN saves allocation and
> free stack metadata to the slab object the same way generic KASAN does.
> 
> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++--------
>  mm/kasan/kasan.h  |   8 ++++
>  mm/kasan/tags.c   |  48 +++++++++++++++++++
>  3 files changed, 153 insertions(+), 19 deletions(-)
>


[...]

> @@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
>  		return;
>  	}
>  
> +	cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
> +

Did you consider to set ARCH_SLAB_MINALIGN instead of this round up?

-- 
Regards,
Vincenzo

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Re: [PATCH v13 00/25] kasan: add software tag-based mode for arm64

[Andrew Morton]

On Tue, 11 Dec 2018 16:00:19 +0000 Will Deacon <will.deacon@arm.com> wrote:

> > Yes, that was the intention of sending v13. Should have I sent a
> > separate patch with v12->v13 fixes instead? I don't know what's the
> > usual way to make changes to the patchset once it's in the mm tree.

I usually convert replacement patches into deltas so people can see
what changed.  In this case it got messy so I dropped v12 and remerged
v13 wholesale.


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Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Andrey Konovalov]

On Tue, Dec 11, 2018 at 5:22 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi Andrey,
>
> On 06/12/2018 12:24, Andrey Konovalov wrote:
> > This commit adds tag-based KASAN specific hooks implementation and
> > adjusts common generic and tag-based KASAN ones.
> >
> > 1. When a new slab cache is created, tag-based KASAN rounds up the size of
> >    the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16).
> >
> > 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow
> >    memory, that corresponds to this object to this tag, and embeds this
> >    tag value into the top byte of the returned pointer.
> >
> > 3. On each kfree tag-based KASAN poisons the shadow memory with a random
> >    tag to allow detection of use-after-free bugs.
> >
> > The rest of the logic of the hook implementation is very much similar to
> > the one provided by generic KASAN. Tag-based KASAN saves allocation and
> > free stack metadata to the slab object the same way generic KASAN does.
> >
> > Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> > Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > ---
> >  mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++--------
> >  mm/kasan/kasan.h  |   8 ++++
> >  mm/kasan/tags.c   |  48 +++++++++++++++++++
> >  3 files changed, 153 insertions(+), 19 deletions(-)
> >
>
>
> [...]
>
> > @@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
> >               return;
> >       }
> >
> > +     cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
> > +
>
> Did you consider to set ARCH_SLAB_MINALIGN instead of this round up?

I didn't know about this macro. Looks like we can use it to do the
same thing. Do you think it's a better solution to redefine
ARCH_SLAB_MINALIGN to KASAN_SHADOW_SCALE_SIZE for arm64 when tag-based
KASAN is enabled instead of adjusting cache->align in
kasan_cache_create?

>
> --
> Regards,
> Vincenzo
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
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Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Vincenzo Frascino]

On 12/12/18 3:04 PM, Andrey Konovalov wrote:
> On Tue, Dec 11, 2018 at 5:22 PM Vincenzo Frascino
> <vincenzo.frascino@arm.com> wrote:
>>
>> Hi Andrey,
>>
>> On 06/12/2018 12:24, Andrey Konovalov wrote:
>>> This commit adds tag-based KASAN specific hooks implementation and
>>> adjusts common generic and tag-based KASAN ones.
>>>
>>> 1. When a new slab cache is created, tag-based KASAN rounds up the size of
>>>    the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16).
>>>
>>> 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow
>>>    memory, that corresponds to this object to this tag, and embeds this
>>>    tag value into the top byte of the returned pointer.
>>>
>>> 3. On each kfree tag-based KASAN poisons the shadow memory with a random
>>>    tag to allow detection of use-after-free bugs.
>>>
>>> The rest of the logic of the hook implementation is very much similar to
>>> the one provided by generic KASAN. Tag-based KASAN saves allocation and
>>> free stack metadata to the slab object the same way generic KASAN does.
>>>
>>> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>>> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
>>> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>>> ---
>>>  mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++--------
>>>  mm/kasan/kasan.h  |   8 ++++
>>>  mm/kasan/tags.c   |  48 +++++++++++++++++++
>>>  3 files changed, 153 insertions(+), 19 deletions(-)
>>>
>>
>>
>> [...]
>>
>>> @@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
>>>               return;
>>>       }
>>>
>>> +     cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
>>> +
>>
>> Did you consider to set ARCH_SLAB_MINALIGN instead of this round up?
> 
> I didn't know about this macro. Looks like we can use it to do the
> same thing. Do you think it's a better solution to redefine
> ARCH_SLAB_MINALIGN to KASAN_SHADOW_SCALE_SIZE for arm64 when tag-based
> KASAN is enabled instead of adjusting cache->align in
> kasan_cache_create?
>

Yes, I think it is better because in this way we do not need to add extra code
to do the rounding.

Curiosity, did you try your patches with SLUB red zoning enabled?
Since the area used for the Redzone is just after the payload, aligning the
object_size independently from the allocator could have side effects, at least
if I understand well how the mechanism works.

Setting ARCH_SLAB_MINALIGN should avoid this as well.

What do you think?

>>
>> --
>> Regards,
>> Vincenzo
>>
>> --
>> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
>> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
>> To post to this group, send email to kasan-dev@googlegroups.com.
>> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/2bf7415e-2724-b3c3-9571-20c8b6d43b92%40arm.com.
>> For more options, visit https://groups.google.com/d/optout.

-- 
Regards,
Vincenzo

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Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Andrey Konovalov]

On Fri, Dec 14, 2018 at 1:34 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> On 12/12/18 3:04 PM, Andrey Konovalov wrote:
> > On Tue, Dec 11, 2018 at 5:22 PM Vincenzo Frascino
> > <vincenzo.frascino@arm.com> wrote:
> >>
> >> Hi Andrey,
> >>
> >> On 06/12/2018 12:24, Andrey Konovalov wrote:
> >>> This commit adds tag-based KASAN specific hooks implementation and
> >>> adjusts common generic and tag-based KASAN ones.
> >>>
> >>> 1. When a new slab cache is created, tag-based KASAN rounds up the size of
> >>>    the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16).
> >>>
> >>> 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow
> >>>    memory, that corresponds to this object to this tag, and embeds this
> >>>    tag value into the top byte of the returned pointer.
> >>>
> >>> 3. On each kfree tag-based KASAN poisons the shadow memory with a random
> >>>    tag to allow detection of use-after-free bugs.
> >>>
> >>> The rest of the logic of the hook implementation is very much similar to
> >>> the one provided by generic KASAN. Tag-based KASAN saves allocation and
> >>> free stack metadata to the slab object the same way generic KASAN does.
> >>>
> >>> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> >>> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> >>> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >>> ---
> >>>  mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++--------
> >>>  mm/kasan/kasan.h  |   8 ++++
> >>>  mm/kasan/tags.c   |  48 +++++++++++++++++++
> >>>  3 files changed, 153 insertions(+), 19 deletions(-)
> >>>
> >>
> >>
> >> [...]
> >>
> >>> @@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
> >>>               return;
> >>>       }
> >>>
> >>> +     cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
> >>> +
> >>
> >> Did you consider to set ARCH_SLAB_MINALIGN instead of this round up?
> >
> > I didn't know about this macro. Looks like we can use it to do the
> > same thing. Do you think it's a better solution to redefine
> > ARCH_SLAB_MINALIGN to KASAN_SHADOW_SCALE_SIZE for arm64 when tag-based
> > KASAN is enabled instead of adjusting cache->align in
> > kasan_cache_create?
> >
>
> Yes, I think it is better because in this way we do not need to add extra code
> to do the rounding.
>
> Curiosity, did you try your patches with SLUB red zoning enabled?
> Since the area used for the Redzone is just after the payload, aligning the
> object_size independently from the allocator could have side effects, at least
> if I understand well how the mechanism works.
>
> Setting ARCH_SLAB_MINALIGN should avoid this as well.
>
> What do you think?

Sounds good to me.

Andrew, how should proceed with this? Send another fixup patch or
resend the whole series?

>
> >>
> >> --
> >> Regards,
> >> Vincenzo
> >>
> >> --
> >> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> >> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> >> To post to this group, send email to kasan-dev@googlegroups.com.
> >> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/2bf7415e-2724-b3c3-9571-20c8b6d43b92%40arm.com.
> >> For more options, visit https://groups.google.com/d/optout.
>
> --
> Regards,
> Vincenzo
>
> --
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Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Andrew Morton]

On Mon, 17 Dec 2018 20:33:42 +0100 Andrey Konovalov <andreyknvl@google.com> wrote:

> > Curiosity, did you try your patches with SLUB red zoning enabled?
> > Since the area used for the Redzone is just after the payload, aligning the
> > object_size independently from the allocator could have side effects, at least
> > if I understand well how the mechanism works.
> >
> > Setting ARCH_SLAB_MINALIGN should avoid this as well.
> >
> > What do you think?
> 
> Sounds good to me.
> 
> Andrew, how should proceed with this? Send another fixup patch or
> resend the whole series?

It depends on how extensive the changes are.  I prefer a fixup, but at
some point it's time to drop it all and start again.


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Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Andrey Konovalov]

On Mon, Dec 17, 2018 at 9:38 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Mon, 17 Dec 2018 20:33:42 +0100 Andrey Konovalov <andreyknvl@google.com> wrote:
>
> > > Curiosity, did you try your patches with SLUB red zoning enabled?
> > > Since the area used for the Redzone is just after the payload, aligning the
> > > object_size independently from the allocator could have side effects, at least
> > > if I understand well how the mechanism works.
> > >
> > > Setting ARCH_SLAB_MINALIGN should avoid this as well.
> > >
> > > What do you think?
> >
> > Sounds good to me.
> >
> > Andrew, how should proceed with this? Send another fixup patch or
> > resend the whole series?
>
> It depends on how extensive the changes are.  I prefer a fixup, but at
> some point it's time to drop it all and start again.

The fixup in only a few lines, so I just sent it as a separate patch
named "[PATCH mm] kasan, arm64: use ARCH_SLAB_MINALIGN instead of
manual aligning".

Thanks!

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