[PATCH v1 00/16] khwasan: kernel hardware assisted address sanitizer

[PATCH v1 00/16] khwasan: kernel hardware assisted address sanitizer

[Andrey Konovalov]

This patchset adds a new mode to KASAN [1], which is called KHWASAN
(Kernel HardWare assisted Address SANitizer). There's still some work to
do and there are a few TODOs in the code, so I'm publishing this as an RFC
to collect some initial feedback.

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 overall idea of the approach used by KHWASAN is the following:

1. By using the Top Byte Ignore 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.

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

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


====== Technical details

KHWASAN is implemented in a very similar way to KASAN. 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
   KHWASAN simply prints a bug report. In case of inline instrumentation,
   clang inserts a brk instruction, and KHWASAN 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 KHWASAN can detect
compared to KASAN: use-after-free after the object has been allocated by
someone else.


====== Benchmarks

The following numbers were collected on Odroid C2 board. Both KASAN and
KHWASAN were used in inline instrumentation mode.

Boot time [1]:
* ~1.7 sec for clean kernel
* ~5.0 sec for KASAN
* ~5.0 sec for KHWASAN

Slab memory usage after boot [2]:
* ~40 kb for clean kernel
* ~105 kb + 1/8th shadow ~= 118 kb for KASAN
* ~47 kb + 1/16th shadow ~= 50 kb for KHWASAN

Network performance [3]:
* 8.33 Gbits/sec for clean kernel
* 3.17 Gbits/sec for KASAN
* 2.85 Gbits/sec for KHWASAN

Note, that KHWASAN (compared to KASAN) doesn't require quarantine.

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


====== 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 LLVM version (r330044 or later).

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


====== Changes

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 (ita??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 [1]).

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/2018/4/19/775

Andrey Konovalov (16):
  khwasan, mm: change kasan hooks signatures
  khwasan: move common kasan and khwasan code to common.c
  khwasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW
  khwasan, arm64: adjust shadow size for CONFIG_KASAN_HW
  khwasan: initialize shadow to 0xff
  khwasan, arm64: untag virt address in __kimg_to_phys
  khwasan, arm64: fix up fault handling logic
  khwasan: add tag related helper functions
  khwasan, arm64: enable top byte ignore for the kernel
  khwasan, mm: perform untagged pointers comparison in krealloc
  khwasan: split out kasan_report.c from report.c
  khwasan: add bug reporting routines
  khwasan: add hooks implementation
  khwasan, arm64: add brk handler for inline instrumentation
  khwasan, mm, arm64: tag non slab memory allocated via pagealloc
  khwasan: update kasan documentation

 Documentation/dev-tools/kasan.rst      | 213 +++++----
 arch/arm64/Kconfig                     |   1 +
 arch/arm64/Makefile                    |   2 +-
 arch/arm64/include/asm/brk-imm.h       |   2 +
 arch/arm64/include/asm/memory.h        |  35 +-
 arch/arm64/include/asm/pgtable-hwdef.h |   1 +
 arch/arm64/kernel/traps.c              |  69 ++-
 arch/arm64/mm/fault.c                  |   3 +
 arch/arm64/mm/kasan_init.c             |  18 +-
 arch/arm64/mm/proc.S                   |   8 +-
 include/linux/compiler-clang.h         |   5 +-
 include/linux/compiler-gcc.h           |   4 +
 include/linux/compiler.h               |   3 +-
 include/linux/kasan.h                  |  84 +++-
 include/linux/mm.h                     |  29 ++
 include/linux/page-flags-layout.h      |  10 +
 lib/Kconfig.kasan                      |  76 +++-
 mm/cma.c                               |   1 +
 mm/kasan/Makefile                      |   9 +-
 mm/kasan/common.c                      | 577 +++++++++++++++++++++++++
 mm/kasan/kasan.c                       | 489 +--------------------
 mm/kasan/kasan.h                       |  94 +++-
 mm/kasan/kasan_report.c                | 155 +++++++
 mm/kasan/khwasan.c                     | 163 +++++++
 mm/kasan/khwasan_report.c              |  60 +++
 mm/kasan/report.c                      | 271 +++---------
 mm/page_alloc.c                        |   1 +
 mm/slab.c                              |  12 +-
 mm/slab.h                              |   2 +-
 mm/slab_common.c                       |   6 +-
 mm/slub.c                              |  18 +-
 scripts/Makefile.kasan                 |  27 +-
 32 files changed, 1606 insertions(+), 842 deletions(-)
 create mode 100644 mm/kasan/common.c
 create mode 100644 mm/kasan/kasan_report.c
 create mode 100644 mm/kasan/khwasan.c
 create mode 100644 mm/kasan/khwasan_report.c

-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 01/16] khwasan, mm: change kasan hooks signatures

[Andrey Konovalov]

KHWASAN will change 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.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/kasan.h | 34 +++++++++++++++++++++++-----------
 mm/kasan/kasan.c      | 24 ++++++++++++++----------
 mm/slab.c             | 12 ++++++------
 mm/slab.h             |  2 +-
 mm/slab_common.c      |  4 ++--
 mm/slub.c             | 16 ++++++++--------
 6 files changed, 54 insertions(+), 38 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index de784fd11d12..cbdc54543803 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -53,14 +53,14 @@ 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_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 {
@@ -105,16 +105,28 @@ static inline void kasan_poison_object_data(struct kmem_cache *cache,
 static inline void kasan_init_slab_obj(struct kmem_cache *cache,
 				const 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/mm/kasan/kasan.c b/mm/kasan/kasan.c
index bc0e68f7dc75..2f5e52d72c2b 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -485,9 +485,9 @@ void kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 	__memset(alloc_info, 0, sizeof(*alloc_info));
 }
 
-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 +528,7 @@ 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 +538,7 @@ 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 +551,12 @@ 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 +566,7 @@ 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 +576,23 @@ 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 2f308253c3d7..5f2aeeb18d3c 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);
@@ -3679,7 +3679,7 @@ __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;
 }
@@ -3715,7 +3715,7 @@ 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 68bdf498da3b..15ef6a0d9c16 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 98dcdc352062..0582004351c4 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1148,7 +1148,7 @@ 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);
@@ -1426,7 +1426,7 @@ 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 44aa7847324a..4fcd1442a761 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1351,10 +1351,10 @@ 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);
+	kmemleak_alloc(*ptr, size, 1, flags);
+	*ptr = kasan_kmalloc_large(*ptr, size, flags);
 }
 
 static __always_inline void kfree_hook(void *x)
@@ -2765,7 +2765,7 @@ 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);
@@ -2793,7 +2793,7 @@ 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);
@@ -3786,7 +3786,7 @@ 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;
 }
@@ -3803,7 +3803,7 @@ 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);
+	kmalloc_large_node_hook(&ptr, size, flags);
 	return ptr;
 }
 
@@ -3831,7 +3831,7 @@ 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;
 }
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 01/16] khwasan, mm: change kasan hooks signatures

[Andrey Ryabinin]

On 05/08/2018 08:20 PM, Andrey Konovalov wrote:

> diff --git a/mm/slub.c b/mm/slub.c
> index 44aa7847324a..4fcd1442a761 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1351,10 +1351,10 @@ 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);
> +	kmemleak_alloc(*ptr, size, 1, flags);
> +	*ptr = kasan_kmalloc_large(*ptr, size, flags);

Why not 'return ptr' like everywhere else?

Re: [PATCH v1 01/16] khwasan, mm: change kasan hooks signatures

[Andrey Konovalov]

On Mon, May 14, 2018 at 6:56 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
>
> On 05/08/2018 08:20 PM, Andrey Konovalov wrote:
>
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 44aa7847324a..4fcd1442a761 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1351,10 +1351,10 @@ 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);
>> +     kmemleak_alloc(*ptr, size, 1, flags);
>> +     *ptr = kasan_kmalloc_large(*ptr, size, flags);
>
> Why not 'return ptr' like everywhere else?

Will fix in v2, thanks!

[PATCH v1 02/16] khwasan: move common kasan and khwasan code to common.c

[Andrey Konovalov]

KHWASAN will reuse a significant part of KASAN code, so move the common
parts to common.c without any functional changes.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/Makefile |   5 +-
 mm/kasan/common.c | 524 ++++++++++++++++++++++++++++++++++++++++++++++
 mm/kasan/kasan.c  | 493 +------------------------------------------
 mm/kasan/kasan.h  |   6 +
 4 files changed, 537 insertions(+), 491 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..ebb48415e4cf
--- /dev/null
+++ b/mm/kasan/common.c
@@ -0,0 +1,524 @@
+/*
+ * This file contains common KASAN and KHWASAN 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);
+}
+
+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);
+}
+
+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;
+
+	alloc_info = get_alloc_info(cache, object);
+	__memset(alloc_info, 0, sizeof(*alloc_info));
+}
+
+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 shadow_size;
+	unsigned long shadow_start;
+
+	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
+	shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
+			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 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;
+
+		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_OFFLINE:
+		vfree((void *)shadow_start);
+	}
+
+	return NOTIFY_OK;
+}
+
+static int __init kasan_memhotplug_init(void)
+{
+	hotplug_memory_notifier(kasan_mem_notifier, 0);
+
+	return 0;
+}
+
+module_init(kasan_memhotplug_init);
+#endif
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 2f5e52d72c2b..13151e437bef 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
@@ -260,70 +184,17 @@ 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)
+unsigned int optimal_redzone(unsigned int object_size)
 {
 	return
 		object_size <= 64        - 16   ? 16 :
@@ -335,46 +206,6 @@ static unsigned int optimal_redzone(unsigned int object_size)
 		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);
@@ -386,274 +217,6 @@ 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;
-
-	alloc_info = get_alloc_info(cache, object);
-	__memset(alloc_info, 0, sizeof(*alloc_info));
-}
-
-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 shadow_size;
-	unsigned long shadow_start;
-
-	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
-	shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
-			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);
@@ -794,53 +357,3 @@ 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 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;
-
-		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_OFFLINE:
-		vfree((void *)shadow_start);
-	}
-
-	return NOTIFY_OK;
-}
-
-static int __init kasan_memhotplug_init(void)
-{
-	hotplug_memory_notifier(kasan_mem_notifier, 0);
-
-	return 0;
-}
-
-module_init(kasan_memhotplug_init);
-#endif
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index c12dcfde2ebd..c39039308b98 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -98,6 +98,7 @@ struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
 					const void *object);
 struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 					const void *object);
+unsigned int optimal_redzone(unsigned int object_size);
 
 static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 {
@@ -105,6 +106,11 @@ 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);
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 02/16] khwasan: move common kasan and khwasan code to common.c

[Andrey Ryabinin]

On 05/08/2018 08:20 PM, Andrey Konovalov wrote:

> +
> +void set_track(struct kasan_track *track, gfp_t flags)

This was -  static inline void set_track(struct kasan_track *track, gfp_t flags)
and still used only locally.

> +{
> +	track->pid = current->pid;
> +	track->stack = save_stack(flags);
> +}
> +



>  /*
>   * 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)
> +unsigned int optimal_redzone(unsigned int object_size)

I'd rather move this in common too.
For khwasan you could just add:
	if (IS_ENABLED(CONFIG_KASAN_HW))
		return 0;

Re: [PATCH v1 02/16] khwasan: move common kasan and khwasan code to common.c

[Andrey Konovalov]

On Tue, May 15, 2018 at 3:28 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
>
> On 05/08/2018 08:20 PM, Andrey Konovalov wrote:
>
>> +
>> +void set_track(struct kasan_track *track, gfp_t flags)
>
> This was -  static inline void set_track(struct kasan_track *track, gfp_t flags)
> and still used only locally.
>
>> +{
>> +     track->pid = current->pid;
>> +     track->stack = save_stack(flags);
>> +}
>> +

Will fix in v2.

>
>
>
>>  /*
>>   * 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)
>> +unsigned int optimal_redzone(unsigned int object_size)
>
> I'd rather move this in common too.
> For khwasan you could just add:
>         if (IS_ENABLED(CONFIG_KASAN_HW))
>                 return 0;
>
>

Will move in v2.

[PATCH v1 03/16] khwasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW

[Andrey Konovalov]

This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic software-only KASAN
   version (the one that exists now);
2. CONFIG_KASAN_HW, that enables KHWASAN.

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

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

This commit also adds empty placeholder (for now) implementation of
KHWASAN specific hooks inserted by the compiler and adjusts common hooks
implementation to compile correctly with each of the config options.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/Kconfig             |  1 +
 include/linux/compiler-clang.h |  5 ++-
 include/linux/compiler-gcc.h   |  4 ++
 include/linux/compiler.h       |  3 +-
 include/linux/kasan.h          | 16 +++++--
 lib/Kconfig.kasan              | 76 ++++++++++++++++++++++++++--------
 mm/kasan/Makefile              |  6 ++-
 mm/kasan/kasan.h               | 11 ++++-
 mm/kasan/khwasan.c             | 75 +++++++++++++++++++++++++++++++++
 mm/slub.c                      |  2 +-
 scripts/Makefile.kasan         | 27 +++++++++++-
 11 files changed, 198 insertions(+), 28 deletions(-)
 create mode 100644 mm/kasan/khwasan.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index eb2cf4938f6d..6553aaa61e6a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -88,6 +88,7 @@ config ARM64
 	select HAVE_ARCH_HUGE_VMAP
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
+	select HAVE_ARCH_KASAN_HW if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 7d98e263e048..72681c6fd418 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -21,13 +21,16 @@
 #define KASAN_ABI_VERSION 5
 
 /* emulate gcc's __SANITIZE_ADDRESS__ flag */
-#if __has_feature(address_sanitizer)
+#if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
 #define __SANITIZE_ADDRESS__
 #endif
 
 #undef __no_sanitize_address
 #define __no_sanitize_address __attribute__((no_sanitize("address")))
 
+#undef __no_sanitize_hwaddress
+#define __no_sanitize_hwaddress __attribute__((no_sanitize("hwaddress")))
+
 /* Clang doesn't have a way to turn it off per-function, yet. */
 #ifdef __noretpoline
 #undef __noretpoline
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index b4bf73f5e38f..00a51feb786d 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -338,6 +338,10 @@
 #define __no_sanitize_address
 #endif
 
+#if !defined(__no_sanitize_hwaddress)
+#define __no_sanitize_hwaddress	/* gcc doesn't support KHWASAN */
+#endif
+
 /*
  * A trick to suppress uninitialized variable warning without generating any
  * code
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index ab4711c63601..6142bae513e8 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -195,7 +195,8 @@ void __read_once_size(const volatile void *p, void *res, int size)
  * 	https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
  */
-# define __no_kasan_or_inline __no_sanitize_address __maybe_unused
+# define __no_kasan_or_inline __no_sanitize_address __no_sanitize_hwaddress \
+			      __maybe_unused
 #else
 # define __no_kasan_or_inline __always_inline
 #endif
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index cbdc54543803..6608aa9b35ac 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);
@@ -94,8 +92,6 @@ 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,
@@ -141,4 +137,16 @@ 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 3d35d062970d..baf2619b7ff4 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -1,33 +1,73 @@
 config HAVE_ARCH_KASAN
 	bool
 
+config HAVE_ARCH_KASAN_HW
+	bool
+
 if HAVE_ARCH_KASAN
 
 config KASAN
-	bool "KASan: runtime memory debugger"
+	bool "KASAN: runtime memory debugger"
+	help
+	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
+	  designed to find out-of-bounds accesses and use-after-free bugs.
+
+choice
+	prompt "KASAN mode"
+	depends on KASAN
+	default KASAN_GENERIC
+	help
+	  KASAN has two modes: KASAN (a classic version, similar to userspace
+	  ASan, enabled with CONFIG_KASAN_GENERIC) and KHWASAN (a version
+	  based on pointer tagging, only for arm64, similar to userspace
+	  HWASan, enabled with CONFIG_KASAN_HW).
+
+config KASAN_GENERIC
+	bool "KASAN: the generic mode"
 	depends on SLUB || (SLAB && !DEBUG_SLAB)
 	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 the generic mode of KASAN.
+	  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 mode consumes about 1/8 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_GENERIC doesn't work with CONFIG_DEBUG_SLAB
+	  (the resulting kernel does not boot).
+
+if HAVE_ARCH_KASAN_HW
+
+config KASAN_HW
+	bool "KHWASAN: the hardware assisted mode"
+	depends on SLUB || (SLAB && !DEBUG_SLAB)
+	select CONSTRUCTORS
+	select STACKDEPOT
+	help
+	  Enabled KHWASAN (KASAN mode based on pointer tagging).
+	  This mode requires Top Byte Ignore support by the CPU and therefore
+	  only supported for arm64.
+	  This feature requires clang revision 330044 or later.
+	  This mode consumes about 1/16 of available memory at kernel start
+	  and introduces an overhead of ~20% for the rest of the allocations.
 	  For better error detection enable CONFIG_STACKTRACE.
-	  Currently CONFIG_KASAN doesn't work with CONFIG_DEBUG_SLAB
+	  Currently CONFIG_KASAN_HW doesn't work with CONFIG_DEBUG_SLAB
 	  (the resulting kernel does not boot).
 
+endif
+
+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
-	  compile time.
+	  This enables further checks in 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
 
 
@@ -52,16 +92,16 @@ 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
 
 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.
+	  kernel debugging features like KASAN.
 
 endif
diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index a6df14bffb6b..14955add96d3 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -2,6 +2,7 @@
 KASAN_SANITIZE := n
 UBSAN_SANITIZE_common.o := n
 UBSAN_SANITIZE_kasan.o := n
+UBSAN_SANITIZE_khwasan.o := n
 KCOV_INSTRUMENT := n
 
 CFLAGS_REMOVE_kasan.o = -pg
@@ -10,5 +11,8 @@ CFLAGS_REMOVE_kasan.o = -pg
 
 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_khwasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
-obj-y := common.o kasan.o report.o kasan_init.o quarantine.o
+obj-$(CONFIG_KASAN) := common.o kasan_init.o report.o
+obj-$(CONFIG_KASAN_GENERIC) += kasan.o quarantine.o
+obj-$(CONFIG_KASAN_HW) += khwasan.o
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index c39039308b98..5091a433f266 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -98,7 +98,15 @@ struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
 					const void *object);
 struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 					const void *object);
+
+#ifdef CONFIG_KASAN_GENERIC
 unsigned int optimal_redzone(unsigned int object_size);
+#else
+static inline unsigned int optimal_redzone(unsigned int object_size)
+{
+	return 0;
+}
+#endif
 
 static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 {
@@ -115,7 +123,8 @@ 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/khwasan.c b/mm/kasan/khwasan.c
new file mode 100644
index 000000000000..e2c3a7f7fd1f
--- /dev/null
+++ b/mm/kasan/khwasan.c
@@ -0,0 +1,75 @@
+/*
+ * This file contains core KHWASAN 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 4fcd1442a761..b3118f7ea92a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2989,7 +2989,7 @@ 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..47023daf5606 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_KASAN
+ifdef CONFIG_KASAN_GENERIC
 ifdef CONFIG_KASAN_INLINE
 	call_threshold := 10000
 else
@@ -45,3 +45,28 @@ endif
 CFLAGS_KASAN_NOSANITIZE := -fno-builtin
 
 endif
+
+ifdef CONFIG_KASAN_HW
+
+ifdef CONFIG_KASAN_INLINE
+    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
+else
+    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
+endif
+
+CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-hwaddress
+
+ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
+    ifneq ($(CONFIG_COMPILE_TEST),y)
+        $(warning Cannot use CONFIG_KASAN_HW: \
+            -fsanitize=hwaddress is not supported by compiler)
+    endif
+else
+    CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-hwaddress \
+        -mllvm -hwasan-instrument-stack=0 \
+        $(instrumentation_flags))
+endif
+
+CFLAGS_KASAN_NOSANITIZE := -fno-builtin
+
+endif
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 03/16] khwasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW

[Andrey Ryabinin]

On 05/08/2018 08:20 PM, Andrey Konovalov wrote:

> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 69552a39951d..47023daf5606 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -1,5 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0
> -ifdef CONFIG_KASAN
> +ifdef CONFIG_KASAN_GENERIC
>  ifdef CONFIG_KASAN_INLINE
>  	call_threshold := 10000
>  else
> @@ -45,3 +45,28 @@ endif
>  CFLAGS_KASAN_NOSANITIZE := -fno-builtin
>  
>  endif
> +
> +ifdef CONFIG_KASAN_HW
> +
> +ifdef CONFIG_KASAN_INLINE
> +    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
> +else
> +    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
> +endif
> +
> +CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-hwaddress
> +
> +ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
> +    ifneq ($(CONFIG_COMPILE_TEST),y)
> +        $(warning Cannot use CONFIG_KASAN_HW: \
> +            -fsanitize=hwaddress is not supported by compiler)
> +    endif
> +else
> +    CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-hwaddress \
> +        -mllvm -hwasan-instrument-stack=0 \
> +        $(instrumentation_flags))
> +endif

So this code does the following:
 1) Warn if compiler doesn't support -fsanitize=kernel-hwaddress
 2) Compile the kernel with all necessary set of the '-fsanitize=kernel-hwaddress -mllvm -hwasan-*' flags if compiler supports all of them.
 3) Compile the kernel with empty CFLAGS_KASAN without a warning if compiler supports 'fsanitize=kernel-hwaddress',
     but doesn't support the rest '-mllvm -hwasan-*' flags.

The last one is just nonsense.


> +
> +CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> +

Does it really has to declared twice?

Re: [PATCH v1 03/16] khwasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW

[Andrey Konovalov]

On Mon, May 14, 2018 at 6:57 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
>
> On 05/08/2018 08:20 PM, Andrey Konovalov wrote:
>
>> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
>> index 69552a39951d..47023daf5606 100644
>> --- a/scripts/Makefile.kasan
>> +++ b/scripts/Makefile.kasan
>> @@ -1,5 +1,5 @@
>>  # SPDX-License-Identifier: GPL-2.0
>> -ifdef CONFIG_KASAN
>> +ifdef CONFIG_KASAN_GENERIC
>>  ifdef CONFIG_KASAN_INLINE
>>       call_threshold := 10000
>>  else
>> @@ -45,3 +45,28 @@ endif
>>  CFLAGS_KASAN_NOSANITIZE := -fno-builtin
>>
>>  endif
>> +
>> +ifdef CONFIG_KASAN_HW
>> +
>> +ifdef CONFIG_KASAN_INLINE
>> +    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
>> +else
>> +    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
>> +endif
>> +
>> +CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-hwaddress
>> +
>> +ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
>> +    ifneq ($(CONFIG_COMPILE_TEST),y)
>> +        $(warning Cannot use CONFIG_KASAN_HW: \
>> +            -fsanitize=hwaddress is not supported by compiler)
>> +    endif
>> +else
>> +    CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-hwaddress \
>> +        -mllvm -hwasan-instrument-stack=0 \
>> +        $(instrumentation_flags))
>> +endif
>
> So this code does the following:
>  1) Warn if compiler doesn't support -fsanitize=kernel-hwaddress
>  2) Compile the kernel with all necessary set of the '-fsanitize=kernel-hwaddress -mllvm -hwasan-*' flags if compiler supports all of them.
>  3) Compile the kernel with empty CFLAGS_KASAN without a warning if compiler supports 'fsanitize=kernel-hwaddress',
>      but doesn't support the rest '-mllvm -hwasan-*' flags.
>
> The last one is just nonsense.

Should I remove "call cc-option" to fix this?

>
>
>> +
>> +CFLAGS_KASAN_NOSANITIZE := -fno-builtin
>> +
>
> Does it really has to declared twice?

Will fix in v2.

Re: [PATCH v1 03/16] khwasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_HW

[Andrey Konovalov]

On Tue, May 22, 2018 at 4:25 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> On Mon, May 14, 2018 at 6:57 PM, Andrey Ryabinin
> <aryabinin@virtuozzo.com> wrote:
>>
>>
>> On 05/08/2018 08:20 PM, Andrey Konovalov wrote:
>>
>>> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
>>> index 69552a39951d..47023daf5606 100644
>>> --- a/scripts/Makefile.kasan
>>> +++ b/scripts/Makefile.kasan
>>> @@ -1,5 +1,5 @@
>>>  # SPDX-License-Identifier: GPL-2.0
>>> -ifdef CONFIG_KASAN
>>> +ifdef CONFIG_KASAN_GENERIC
>>>  ifdef CONFIG_KASAN_INLINE
>>>       call_threshold := 10000
>>>  else
>>> @@ -45,3 +45,28 @@ endif
>>>  CFLAGS_KASAN_NOSANITIZE := -fno-builtin
>>>
>>>  endif
>>> +
>>> +ifdef CONFIG_KASAN_HW
>>> +
>>> +ifdef CONFIG_KASAN_INLINE
>>> +    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
>>> +else
>>> +    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
>>> +endif
>>> +
>>> +CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-hwaddress
>>> +
>>> +ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
>>> +    ifneq ($(CONFIG_COMPILE_TEST),y)
>>> +        $(warning Cannot use CONFIG_KASAN_HW: \
>>> +            -fsanitize=hwaddress is not supported by compiler)
>>> +    endif
>>> +else
>>> +    CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-hwaddress \
>>> +        -mllvm -hwasan-instrument-stack=0 \
>>> +        $(instrumentation_flags))
>>> +endif
>>
>> So this code does the following:
>>  1) Warn if compiler doesn't support -fsanitize=kernel-hwaddress
>>  2) Compile the kernel with all necessary set of the '-fsanitize=kernel-hwaddress -mllvm -hwasan-*' flags if compiler supports all of them.
>>  3) Compile the kernel with empty CFLAGS_KASAN without a warning if compiler supports 'fsanitize=kernel-hwaddress',
>>      but doesn't support the rest '-mllvm -hwasan-*' flags.
>>
>> The last one is just nonsense.
>
> Should I remove "call cc-option" to fix this?

Nevermind, will fix in v2.

>
>>
>>
>>> +
>>> +CFLAGS_KASAN_NOSANITIZE := -fno-builtin
>>> +
>>
>> Does it really has to declared twice?
>
> Will fix in v2.

[PATCH v1 04/16] khwasan, arm64: adjust shadow size for CONFIG_KASAN_HW

[Andrey Konovalov]

KWHASAN 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 KHWASAN is enabled.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/Makefile             |  2 +-
 arch/arm64/include/asm/memory.h | 13 +++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 87f7d2f9f17c..99c9649c57b1 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -99,7 +99,7 @@ endif
 # 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_SCALE_SHIFT := $(if $(CONFIG_KASAN_HW), 4, 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 49d99214f43c..6d084431b7f7 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -74,12 +74,17 @@
 #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.
+ * KASAN and KHWASAN 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
+#ifdef CONFIG_KASAN_GENERIC
 #define KASAN_SHADOW_SCALE_SHIFT 3
+#endif
+#ifdef CONFIG_KASAN_HW
+#define KASAN_SHADOW_SCALE_SHIFT 4
+#endif
+#ifdef CONFIG_KASAN
 #define KASAN_SHADOW_SIZE	(UL(1) << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
 #define KASAN_THREAD_SHIFT	1
 #else
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 05/16] khwasan: initialize shadow to 0xff

[Andrey Konovalov]

A KHWASAN 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 KHWASAN we
need to initialize shadow memory to 0xff. This commit does that.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/kasan_init.c | 16 ++++++++++++++--
 include/linux/kasan.h      |  8 ++++++++
 mm/kasan/common.c          |  3 ++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 12145874c02b..7a31e8ccbad2 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -44,6 +44,15 @@ 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_virt_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)
 {
@@ -89,7 +98,9 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 
 	do {
 		phys_addr_t page_phys = early ? __pa_symbol(kasan_zero_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)));
@@ -139,6 +150,7 @@ asmlinkage void __init kasan_early_init(void)
 		KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
+
 	kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
 			   true);
 }
@@ -235,7 +247,7 @@ void __init kasan_init(void)
 		set_pte(&kasan_zero_pte[i],
 			pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
 
-	memset(kasan_zero_page, 0, PAGE_SIZE);
+	memset(kasan_zero_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 6608aa9b35ac..336385baf926 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -139,6 +139,8 @@ 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);
 
@@ -149,4 +151,10 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 
 #endif /* CONFIG_KASAN_GENERIC */
 
+#ifdef CONFIG_KASAN_HW
+
+#define KASAN_SHADOW_INIT 0xFF
+
+#endif /* CONFIG_KASAN_HW */
+
 #endif /* LINUX_KASAN_H */
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index ebb48415e4cf..0c1159feaf5e 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -454,11 +454,12 @@ 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;
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 06/16] khwasan, arm64: untag virt address in __kimg_to_phys

[Andrey Konovalov]

__kimg_to_phys (which is used by virt_to_phys) assumes that the top byte
of the address is 0xff, which isn't always the case with KHWASAN enabled.
The solution is to reset the tag in __kimg_to_phys.

__lm_to_phys doesn't require any fixups, as it zeroes out the top byte
with the current implementation.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/memory.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 6d084431b7f7..f206273469b5 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -92,6 +92,12 @@
 #define KASAN_THREAD_SHIFT	0
 #endif
 
+#ifdef CONFIG_KASAN_HW
+#define KASAN_TAG_SHIFTED(tag)		((unsigned long)(tag) << 56)
+#define KASAN_SET_TAG(addr, tag)	(((addr) & ~KASAN_TAG_SHIFTED(0xff)) | \
+						KASAN_TAG_SHIFTED(tag))
+#endif
+
 #define MIN_THREAD_SHIFT	(14 + KASAN_THREAD_SHIFT)
 
 /*
@@ -225,7 +231,12 @@ static inline unsigned long kaslr_offset(void)
 #define __is_lm_address(addr)	(!!((addr) & BIT(VA_BITS - 1)))
 
 #define __lm_to_phys(addr)	(((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
+
+#ifdef CONFIG_KASAN_HW
+#define __kimg_to_phys(addr)	(KASAN_SET_TAG((addr), 0xff) - kimage_voffset)
+#else
 #define __kimg_to_phys(addr)	((addr) - kimage_voffset)
+#endif
 
 #define __virt_to_phys_nodebug(x) ({					\
 	phys_addr_t __x = (phys_addr_t)(x);				\
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 07/16] khwasan, arm64: fix up fault handling logic

[Andrey Konovalov]

show_pte in arm64 fault handling relies on the fact that the top byte of
a kernel pointer is 0xff, which isn't always the case with KHWASAN enabled.
Reset the top byte.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/fault.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 4165485e8b6e..e834fe76f5d2 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -32,6 +32,7 @@
 #include <linux/perf_event.h>
 #include <linux/preempt.h>
 #include <linux/hugetlb.h>
+#include <linux/kasan.h>
 
 #include <asm/bug.h>
 #include <asm/cmpxchg.h>
@@ -134,6 +135,8 @@ void show_pte(unsigned long addr)
 	pgd_t *pgdp;
 	pgd_t pgd;
 
+	addr = (unsigned long)khwasan_reset_tag((void *)addr);
+
 	if (addr < TASK_SIZE) {
 		/* TTBR0 */
 		mm = current->active_mm;
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 08/16] khwasan: 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 (set to 0xff) the top byte.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/mm/kasan_init.c |  2 ++
 include/linux/kasan.h      | 23 ++++++++++++++++
 mm/kasan/kasan.h           | 55 ++++++++++++++++++++++++++++++++++++++
 mm/kasan/khwasan.c         | 48 +++++++++++++++++++++++++++++++++
 4 files changed, 128 insertions(+)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 7a31e8ccbad2..e7f37c0b7e14 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -250,6 +250,8 @@ void __init kasan_init(void)
 	memset(kasan_zero_page, KASAN_SHADOW_INIT, PAGE_SIZE);
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 
+	khwasan_init();
+
 	/* 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 336385baf926..d7624b879d86 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -155,6 +155,29 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 
 #define KASAN_SHADOW_INIT 0xFF
 
+void khwasan_init(void);
+
+void *khwasan_set_tag(const void *addr, u8 tag);
+u8 khwasan_get_tag(const void *addr);
+void *khwasan_reset_tag(const void *ptr);
+
+#else /* CONFIG_KASAN_HW */
+
+static inline void khwasan_init(void) { }
+
+static inline void *khwasan_set_tag(const void *addr, u8 tag)
+{
+	return (void *)addr;
+}
+static inline u8 khwasan_get_tag(const void *addr)
+{
+	return 0xFF;
+}
+static inline void *khwasan_reset_tag(const void *ptr)
+{
+	return (void *)ptr;
+}
+
 #endif /* CONFIG_KASAN_HW */
 
 #endif /* LINUX_KASAN_H */
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 5091a433f266..cd51ae9d8149 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 KHWASAN_TAG_KERNEL	0xFF /* native kernel pointers tag */
+#define KHWASAN_TAG_INVALID	0xFE /* inaccessible memory tag */
+#define KHWASAN_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 */
@@ -135,6 +139,57 @@ static inline void quarantine_reduce(void) { }
 static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
 #endif
 
+#ifdef CONFIG_KASAN_HW
+
+#define KHWASAN_TAG_SHIFT 56
+#define KHWASAN_TAG_MASK (0xFFUL << KHWASAN_TAG_SHIFT)
+
+u8 random_tag(void);
+
+static inline void *set_tag(const void *addr, u8 tag)
+{
+	u64 a = (u64)addr;
+
+	a &= ~KHWASAN_TAG_MASK;
+	a |= ((u64)tag << KHWASAN_TAG_SHIFT);
+
+	return (void *)a;
+}
+
+static inline u8 get_tag(const void *addr)
+{
+	return (u8)((u64)addr >> KHWASAN_TAG_SHIFT);
+}
+
+static inline void *reset_tag(const void *addr)
+{
+	return set_tag(addr, KHWASAN_TAG_KERNEL);
+}
+
+#else /* CONFIG_KASAN_HW */
+
+static inline u8 random_tag(void)
+{
+	return 0;
+}
+
+static inline void *set_tag(const void *addr, u8 tag)
+{
+	return (void *)addr;
+}
+
+static inline u8 get_tag(const void *addr)
+{
+	return 0;
+}
+
+static inline void *reset_tag(const void *addr)
+{
+	return (void *)addr;
+}
+
+#endif /* CONFIG_KASAN_HW */
+
 /*
  * Exported functions for interfaces called from assembly or from generated
  * code. Declarations here to avoid warning about missing declarations.
diff --git a/mm/kasan/khwasan.c b/mm/kasan/khwasan.c
index e2c3a7f7fd1f..4e253c1e4d35 100644
--- a/mm/kasan/khwasan.c
+++ b/mm/kasan/khwasan.c
@@ -38,6 +38,54 @@
 #include "kasan.h"
 #include "../slab.h"
 
+static DEFINE_PER_CPU(u32, prng_state);
+
+void khwasan_init(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 KHWASAN is meant to be used a probabilistic bug-detection
+ * debug feature, this doesna??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 % (KHWASAN_TAG_MAX + 1));
+}
+
+void *khwasan_set_tag(const void *addr, u8 tag)
+{
+	return set_tag(addr, tag);
+}
+
+u8 khwasan_get_tag(const void *addr)
+{
+	return get_tag(addr);
+}
+
+void *khwasan_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)
 {
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 08/16] khwasan: add tag related helper functions

[Andrey Ryabinin]

On 05/08/2018 08:20 PM, Andrey Konovalov wrote:

> +	for_each_possible_cpu(cpu) {
> +		per_cpu(prng_state, cpu) = get_random_u32();
> +	}


Use checkpatch please.

Re: [PATCH v1 08/16] khwasan: add tag related helper functions

[Andrey Konovalov]

On Mon, May 14, 2018 at 6:58 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
>
> On 05/08/2018 08:20 PM, Andrey Konovalov wrote:
>
>> +     for_each_possible_cpu(cpu) {
>> +             per_cpu(prng_state, cpu) = get_random_u32();
>> +     }
>
>
> Use checkpatch please.

Checkpatch doesn't report this, will fix in v2.

[PATCH v1 09/16] khwasan, arm64: enable top byte ignore for the kernel

[Andrey Konovalov]

KHWASAN 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 KHWASAN is used.

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 fd208eac9f2a..483aceedad76 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -289,6 +289,7 @@
 #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 5f9a73a4452c..f3dfcd74a285 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_HW
+#define TCR_KASAN_FLAGS TCR_TBI1
+#else
+#define TCR_KASAN_FLAGS 0
+#endif
+
 #define MAIR(attr, mt)	((attr) << ((mt) * 8))
 
 /*
@@ -439,7 +445,7 @@ 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
 
 	/*
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 10/16] khwasan, 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. KHWASAN 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.

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 0582004351c4..451b094b8c5b 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1478,7 +1478,7 @@ 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 && khwasan_reset_tag(p) != khwasan_reset_tag(ret))
 		kfree(p);
 
 	return ret;
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 11/16] khwasan: split out kasan_report.c from report.c

[Andrey Konovalov]

This patch moves KASAN specific error reporting routines to kasan_report.c
without any functional changes, leaving common error reporting code in
report.c to be later reused by KHWASAN.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/Makefile         |   4 +-
 mm/kasan/kasan.h          |   7 ++
 mm/kasan/kasan_report.c   | 158 +++++++++++++++++++++++++
 mm/kasan/khwasan_report.c |  39 +++++++
 mm/kasan/report.c         | 234 +++++++++-----------------------------
 5 files changed, 257 insertions(+), 185 deletions(-)
 create mode 100644 mm/kasan/kasan_report.c
 create mode 100644 mm/kasan/khwasan_report.c

diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
index 14955add96d3..7ef536390365 100644
--- a/mm/kasan/Makefile
+++ b/mm/kasan/Makefile
@@ -14,5 +14,5 @@ CFLAGS_kasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 CFLAGS_khwasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
 
 obj-$(CONFIG_KASAN) := common.o kasan_init.o report.o
-obj-$(CONFIG_KASAN_GENERIC) += kasan.o quarantine.o
-obj-$(CONFIG_KASAN_HW) += khwasan.o
+obj-$(CONFIG_KASAN_GENERIC) += kasan.o kasan_report.o quarantine.o
+obj-$(CONFIG_KASAN_HW) += khwasan.o khwasan_report.o
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index cd51ae9d8149..a76aee9e095f 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -118,11 +118,18 @@ 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/kasan_report.c b/mm/kasan/kasan_report.c
new file mode 100644
index 000000000000..2d8decbecbd5
--- /dev/null
+++ b/mm/kasan/kasan_report.c
@@ -0,0 +1,158 @@
+/*
+ * This file contains 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/khwasan_report.c b/mm/kasan/khwasan_report.c
new file mode 100644
index 000000000000..2edbc3c76be5
--- /dev/null
+++ b/mm/kasan/khwasan_report.c
@@ -0,0 +1,39 @@
+/*
+ * This file contains KHWASAN 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";
+}
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 5c169aa688fd..155247a6f8a8 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 KASAN and KHWASAN 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);
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 12/16] khwasan: add bug reporting routines

[Andrey Konovalov]

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

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

2. KHWASAN reports all bugs with the "KASAN: invalid-access" header. This
   is done, so various external tools that already parse the kernel logs
   looking for KASAN reports wouldn't need to be changed.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/kasan.h     |  3 +++
 mm/kasan/kasan.h          |  7 +++++
 mm/kasan/kasan_report.c   |  7 ++---
 mm/kasan/khwasan_report.c | 21 +++++++++++++++
 mm/kasan/report.c         | 57 +++++++++++++++++++++------------------
 5 files changed, 64 insertions(+), 31 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index d7624b879d86..e209027f3b52 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -161,6 +161,9 @@ void *khwasan_set_tag(const void *addr, u8 tag);
 u8 khwasan_get_tag(const void *addr);
 void *khwasan_reset_tag(const void *ptr);
 
+void kasan_report(unsigned long addr, size_t size,
+			bool write, unsigned long ip);
+
 #else /* CONFIG_KASAN_HW */
 
 static inline void khwasan_init(void) { }
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index a76aee9e095f..620941d1e84f 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -128,8 +128,15 @@ 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);
 
+#ifdef CONFIG_KASAN_HW
+void print_tags(u8 addr_tag, const void *addr);
+#else
+static inline void print_tags(u8 addr_tag, const void *addr) { }
+#endif
+
 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/kasan_report.c b/mm/kasan/kasan_report.c
index 2d8decbecbd5..fdf2d77e3125 100644
--- a/mm/kasan/kasan_report.c
+++ b/mm/kasan/kasan_report.c
@@ -33,10 +33,10 @@
 #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 *first_bad_addr = addr;
 
 	while (!shadow_val && first_bad_addr < addr + size) {
 		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
@@ -50,9 +50,6 @@ 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/khwasan_report.c b/mm/kasan/khwasan_report.c
index 2edbc3c76be5..51238b404b08 100644
--- a/mm/kasan/khwasan_report.c
+++ b/mm/kasan/khwasan_report.c
@@ -37,3 +37,24 @@ 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 *untagged_addr = reset_tag(addr);
+	u8 *shadow = (u8 *)kasan_mem_to_shadow(untagged_addr);
+	void *first_bad_addr = untagged_addr;
+
+	while (*shadow == tag && first_bad_addr < untagged_addr + size) {
+		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
+		shadow = (u8 *)kasan_mem_to_shadow(first_bad_addr);
+	}
+	return first_bad_addr;
+}
+
+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);
+}
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 155247a6f8a8..e031c78f2e52 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);
 }
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 13/16] khwasan: add hooks implementation

[Andrey Konovalov]

This commit adds KHWASAN specific hooks implementation and adjusts
common KASAN and KHWASAN ones.

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

2. On each kmalloc KHWASAN 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 KHWASAN 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 KASAN. KHWASAN saves allocation and free stack metadata
to the slab object the same was KASAN does this.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/common.c  | 73 ++++++++++++++++++++++++++++++++++++----------
 mm/kasan/kasan.h   |  8 +++++
 mm/kasan/khwasan.c | 40 +++++++++++++++++++++++++
 3 files changed, 105 insertions(+), 16 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 0c1159feaf5e..0654bf97257b 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -140,6 +140,9 @@ 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 */
+	address = reset_tag(address);
+
 	shadow_start = kasan_mem_to_shadow(address);
 	shadow_end = kasan_mem_to_shadow(address + size);
 
@@ -148,11 +151,15 @@ 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);
+	kasan_poison_shadow(address, size, get_tag(address));
 
 	if (size & KASAN_SHADOW_MASK) {
 		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
-		*shadow = size & KASAN_SHADOW_MASK;
+
+		if (IS_ENABLED(CONFIG_KASAN_HW))
+			*shadow = get_tag(address);
+		else
+			*shadow = size & KASAN_SHADOW_MASK;
 	}
 }
 
@@ -216,6 +223,7 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 			slab_flags_t *flags)
 {
 	unsigned int orig_size = *size;
+	unsigned int redzone_size = 0;
 	int redzone_adjust;
 
 	/* Add alloc meta. */
@@ -223,20 +231,20 @@ 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.
@@ -306,18 +314,30 @@ void kasan_init_slab_obj(struct kmem_cache *cache, const void *object)
 
 void *kasan_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
 {
-	return kasan_kmalloc(cache, object, cache->object_size, flags);
+	object = kasan_kmalloc(cache, object, cache->object_size, flags);
+	if (IS_ENABLED(CONFIG_KASAN_HW) && unlikely(cache->ctor)) {
+		/*
+		 * Cache constructor might use object's pointer value to
+		 * initialize some of its fields.
+		 */
+		cache->ctor(object);
+	}
+	return object;
 }
 
 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 			      unsigned long ip, bool quarantine)
 {
 	s8 shadow_byte;
+	u8 tag;
 	unsigned long rounded_up_size;
 
+	tag = get_tag(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(set_tag(object, tag), ip);
 		return true;
 	}
 
@@ -326,20 +346,29 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 		return false;
 
 	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
+#ifdef CONFIG_KASAN_GENERIC
 	if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
 		kasan_report_invalid_free(object, ip);
 		return true;
 	}
+#else
+	if (tag != (u8)shadow_byte) {
+		kasan_report_invalid_free(set_tag(object, tag), ip);
+		return true;
+	}
+#endif
 
 	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)
@@ -352,6 +381,7 @@ 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();
@@ -364,14 +394,19 @@ 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);
 
+#ifdef CONFIG_KASAN_GENERIC
 	kasan_unpoison_shadow(object, size);
+#else
+	tag = random_tag();
+	kasan_poison_shadow(object, redzone_start - (unsigned long)object, tag);
+#endif
 	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);
 
@@ -380,6 +415,7 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 	struct page *page;
 	unsigned long redzone_start;
 	unsigned long redzone_end;
+	u8 tag;
 
 	if (gfpflags_allow_blocking(flags))
 		quarantine_reduce();
@@ -392,11 +428,16 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 				KASAN_SHADOW_SCALE_SIZE);
 	redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 
+#ifdef CONFIG_KASAN_GENERIC
 	kasan_unpoison_shadow(ptr, size);
+#else
+	tag = random_tag();
+	kasan_poison_shadow(ptr, redzone_start - (unsigned long)ptr, tag);
+#endif
 	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 		KASAN_PAGE_REDZONE);
 
-	return (void *)ptr;
+	return set_tag(ptr, tag);
 }
 
 void *kasan_krealloc(const void *object, size_t size, gfp_t flags)
@@ -421,7 +462,7 @@ 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;
 		}
@@ -434,7 +475,7 @@ 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 620941d1e84f..06b70d296411 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -12,10 +12,18 @@
 #define KHWASAN_TAG_INVALID	0xFE /* inaccessible memory tag */
 #define KHWASAN_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         KHWASAN_TAG_INVALID
+#define KASAN_PAGE_REDZONE      KHWASAN_TAG_INVALID
+#define KASAN_KMALLOC_REDZONE   KHWASAN_TAG_INVALID
+#define KASAN_KMALLOC_FREE      KHWASAN_TAG_INVALID
+#endif
+
 #define KASAN_GLOBAL_REDZONE    0xFA  /* redzone for global variable */
 
 /*
diff --git a/mm/kasan/khwasan.c b/mm/kasan/khwasan.c
index 4e253c1e4d35..b4919ef74741 100644
--- a/mm/kasan/khwasan.c
+++ b/mm/kasan/khwasan.c
@@ -89,15 +89,52 @@ void *khwasan_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;
+
+	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 KHWASAN_TAG_KERNEL (0xFF).
+	 */
+	if (tag == KHWASAN_TAG_KERNEL)
+		return;
+
+	untagged_addr = reset_tag((const void *)addr);
+	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)
 
@@ -109,15 +146,18 @@ 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);
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 13/16] khwasan: add hooks implementation

[Andrey Ryabinin]

On 05/08/2018 08:20 PM, Andrey Konovalov wrote:

>  
>  static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
>  			      unsigned long ip, bool quarantine)
>  {
>  	s8 shadow_byte;
> +	u8 tag;
>  	unsigned long rounded_up_size;
>  
> +	tag = get_tag(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(set_tag(object, tag), ip);

Using variable to store untagged_object pointer, instead of tagging/untagging back and forth would make the
code easier to follow.

>  		return true;
>  	}
>  
> @@ -326,20 +346,29 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
>  		return false;
>  
>  	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
> +#ifdef CONFIG_KASAN_GENERIC
>  	if (shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE) {
>  		kasan_report_invalid_free(object, ip);
>  		return true;
>  	}
> +#else
> +	if (tag != (u8)shadow_byte) {
> +		kasan_report_invalid_free(set_tag(object, tag), ip);
> +		return true;
> +	}
> +#endif



static bool inline shadow_ivalid(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,

...
	if (shadow_invalid(tag, shadow_byte)) {
		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)))
> +	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)
> @@ -352,6 +381,7 @@ 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();
> @@ -364,14 +394,19 @@ 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);
>  
> +#ifdef CONFIG_KASAN_GENERIC
>  	kasan_unpoison_shadow(object, size);
> +#else
> +	tag = random_tag();
> +	kasan_poison_shadow(object, redzone_start - (unsigned long)object, tag);
> +#

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 7cd4a4e8c3be..f11d6059fc06 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -404,12 +404,9 @@ 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);
 
-#ifdef CONFIG_KASAN_GENERIC
-	kasan_unpoison_shadow(object, size);
-#else
 	tag = random_tag();
-	kasan_poison_shadow(object, redzone_start - (unsigned long)object, tag);
-#endif
+	kasan_unpoison_shadow(set_tag(object, tag), size);
+
 	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 		KASAN_KMALLOC_REDZONE);
 


>  	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);
>  



> @@ -380,6 +415,7 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
>  	struct page *page;
>  	unsigned long redzone_start;
>  	unsigned long redzone_end;
> +	u8 tag;
>  
>  	if (gfpflags_allow_blocking(flags))
>  		quarantine_reduce();
> @@ -392,11 +428,16 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
>  				KASAN_SHADOW_SCALE_SIZE);
>  	redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
>  
> +#ifdef CONFIG_KASAN_GENERIC
>  	kasan_unpoison_shadow(ptr, size);
> +#else
> +	tag = random_tag();
> +	kasan_poison_shadow(ptr, redzone_start - (unsigned long)ptr, tag);
> +#endif
>  	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
>  		KASAN_PAGE_REDZONE);
>  
> -	return (void *)ptr;
> +	return set_tag(ptr, tag);
>  }

kasan_kmalloc_large() should be left untouched. It works correctly as is in both cases.
ptr comes from page allocator already already tagged at this point.

Re: [PATCH v1 13/16] khwasan: add hooks implementation

[Andrey Konovalov]

On Tue, May 15, 2018 at 3:13 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
> Using variable to store untagged_object pointer, instead of tagging/untagging back and forth would make the
> code easier to follow.

> static bool inline shadow_ivalid(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,
>
> ...
>         if (shadow_invalid(tag, shadow_byte)) {
>                 kasan_report_invalid_free(object, ip);
>                 return true;
>         }
>

> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 7cd4a4e8c3be..f11d6059fc06 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -404,12 +404,9 @@ 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);
>
> -#ifdef CONFIG_KASAN_GENERIC
> -       kasan_unpoison_shadow(object, size);
> -#else
>         tag = random_tag();
> -       kasan_poison_shadow(object, redzone_start - (unsigned long)object, tag);
> -#endif
> +       kasan_unpoison_shadow(set_tag(object, tag), size);
> +
>         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
>                 KASAN_KMALLOC_REDZONE);

> kasan_kmalloc_large() should be left untouched. It works correctly as is in both cases.
> ptr comes from page allocator already already tagged at this point.

Will fix all in v2, thanks!

[PATCH v1 14/16] khwasan, arm64: add brk handler for inline instrumentation

[Andrey Konovalov]

KHWASAN 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 add a KHWASAN 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.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/brk-imm.h |  2 +
 arch/arm64/kernel/traps.c        | 69 +++++++++++++++++++++++++++++++-
 2 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/brk-imm.h b/arch/arm64/include/asm/brk-imm.h
index ed693c5bcec0..e4a7013321dc 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: KHWASAN 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 KHWASAN_BRK_IMM			0x900
 
 #endif
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 8bbdc17e49df..2234e3a4cc35 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>
@@ -269,10 +270,14 @@ void arm64_notify_die(const char *str, struct pt_regs *regs,
 	}
 }
 
-void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
+void __arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
 {
 	regs->pc += size;
+}
 
+void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
+{
+	__arm64_skip_faulting_instruction(regs, size);
 	/*
 	 * If we were single stepping, we want to get the step exception after
 	 * we return from the trap.
@@ -790,7 +795,7 @@ static int bug_handler(struct pt_regs *regs, unsigned int esr)
 	}
 
 	/* If thread survives, skip over the BUG instruction and continue: */
-	arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
+	__arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE);
 	return DBG_HOOK_HANDLED;
 }
 
@@ -800,6 +805,59 @@ static struct break_hook bug_break_hook = {
 	.fn = bug_handler,
 };
 
+#ifdef CONFIG_KASAN_HW
+
+#define KHWASAN_ESR_RECOVER	0x20
+#define KHWASAN_ESR_WRITE	0x10
+#define KHWASAN_ESR_SIZE_MASK	0x0f
+#define KHWASAN_ESR_SIZE(esr)	(1 << ((esr) & KHWASAN_ESR_SIZE_MASK))
+
+static int khwasan_handler(struct pt_regs *regs, unsigned int esr)
+{
+	bool recover = esr & KHWASAN_ESR_RECOVER;
+	bool write = esr & KHWASAN_ESR_WRITE;
+	size_t size = KHWASAN_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. KHWASAN reporting is disabled in some contexts (for example when
+	 * the allocator accesses slab object metadata; same is true for KASAN;
+	 * 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 - KHWASAN", 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 KHWASAN_ESR_VAL (0xf2000000 | KHWASAN_BRK_IMM)
+#define KHWASAN_ESR_MASK 0xffffff00
+
+static struct break_hook khwasan_break_hook = {
+	.esr_val = KHWASAN_ESR_VAL,
+	.esr_mask = KHWASAN_ESR_MASK,
+	.fn = khwasan_handler,
+};
+#endif
+
 /*
  * Initial handler for AArch64 BRK exceptions
  * This handler only used until debug_traps_init().
@@ -807,6 +865,10 @@ static struct break_hook bug_break_hook = {
 int __init early_brk64(unsigned long addr, unsigned int esr,
 		struct pt_regs *regs)
 {
+#ifdef CONFIG_KASAN_HW
+	if ((esr & KHWASAN_ESR_MASK) == KHWASAN_ESR_VAL)
+		return khwasan_handler(regs, esr) != DBG_HOOK_HANDLED;
+#endif
 	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
 }
 
@@ -814,4 +876,7 @@ int __init early_brk64(unsigned long addr, unsigned int esr,
 void __init trap_init(void)
 {
 	register_break_hook(&bug_break_hook);
+#ifdef CONFIG_KASAN_HW
+	register_break_hook(&khwasan_break_hook);
+#endif
 }
-- 
2.17.0.441.gb46fe60e1d-goog

[PATCH v1 15/16] khwasan, mm, arm64: tag non slab memory allocated via pagealloc

[Andrey Konovalov]

KWHASAN 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.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 arch/arm64/include/asm/memory.h   | 11 +++++++++++
 include/linux/mm.h                | 29 +++++++++++++++++++++++++++++
 include/linux/page-flags-layout.h | 10 ++++++++++
 mm/cma.c                          |  1 +
 mm/kasan/common.c                 | 15 +++++++++++++--
 mm/page_alloc.c                   |  1 +
 6 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index f206273469b5..9ec78a44c5ff 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -304,7 +304,18 @@ 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))
 
+#ifndef CONFIG_KASAN_HW
 #define page_to_virt(page)	((void *)((__page_to_voff(page)) | PAGE_OFFSET))
+#else
+#define page_to_virt(page)	({					\
+	unsigned long __addr =						\
+		((__page_to_voff(page)) | PAGE_OFFSET);			\
+	if (!PageSlab((struct page *)page))				\
+		__addr = KASAN_SET_TAG(__addr, page_kasan_tag(page));	\
+	((void *)__addr);						\
+})
+#endif
+
 #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 1ac1f06a4be6..d6d596824803 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -770,6 +770,7 @@ int 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
@@ -780,6 +781,7 @@ int 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
@@ -802,6 +804,7 @@ int 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)
@@ -1021,6 +1024,32 @@ static inline bool cpupid_match_pid(struct task_struct *task, int cpupid)
 }
 #endif /* CONFIG_NUMA_BALANCING */
 
+#ifdef CONFIG_KASAN_HW
+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..8dbad17664c2 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_HW
+#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 aa40e6c7b042..f657db289bba 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -526,6 +526,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 	}
 
 	trace_cma_alloc(pfn, page, count, align);
+	page_kasan_tag_reset(page);
 
 	if (ret && !(gfp_mask & __GFP_NOWARN)) {
 		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 0654bf97257b..7cd4a4e8c3be 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -207,8 +207,18 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
 
 void kasan_alloc_pages(struct page *page, unsigned int order)
 {
+#ifdef CONFIG_KASAN_GENERIC
 	if (likely(!PageHighMem(page)))
 		kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
+#else
+	if (!PageSlab(page)) {
+		u8 tag = random_tag();
+
+		kasan_poison_shadow(page_address(page), PAGE_SIZE << order,
+					tag);
+		page_kasan_tag_set(page, tag);
+	}
+#endif
 }
 
 void kasan_free_pages(struct page *page, unsigned int order)
@@ -433,6 +443,7 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
 #else
 	tag = random_tag();
 	kasan_poison_shadow(ptr, redzone_start - (unsigned long)ptr, tag);
+	page_kasan_tag_set(page, tag);
 #endif
 	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 		KASAN_PAGE_REDZONE);
@@ -462,7 +473,7 @@ 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;
 		}
@@ -475,7 +486,7 @@ 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 905db9d7962f..54df9c852c6e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1179,6 +1179,7 @@ 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
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 15/16] khwasan, mm, arm64: tag non slab memory allocated via pagealloc

[Andrey Ryabinin]

On 05/08/2018 08:21 PM, Andrey Konovalov wrote:

> +#ifndef CONFIG_KASAN_HW
>  #define page_to_virt(page)	((void *)((__page_to_voff(page)) | PAGE_OFFSET))
> +#else
> +#define page_to_virt(page)	({					\
> +	unsigned long __addr =						\
> +		((__page_to_voff(page)) | PAGE_OFFSET);			\
> +	if (!PageSlab((struct page *)page))				\
> +		__addr = KASAN_SET_TAG(__addr, page_kasan_tag(page));	\

You could avoid 'if (!PageSlab())' check by adding page_kasan_tag_reset() into kasan_poison_slab().


> +	((void *)__addr);						\
> +})
> +#endif
> +
>  #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/mm/cma.c b/mm/cma.c
> index aa40e6c7b042..f657db289bba 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -526,6 +526,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>  	}
>  
>  	trace_cma_alloc(pfn, page, count, align);
> +	page_kasan_tag_reset(page);
  

Why? Comment needed.


>  	if (ret && !(gfp_mask & __GFP_NOWARN)) {
>  		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 0654bf97257b..7cd4a4e8c3be 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -207,8 +207,18 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
>  
>  void kasan_alloc_pages(struct page *page, unsigned int order)
>  {
> +#ifdef CONFIG_KASAN_GENERIC
>  	if (likely(!PageHighMem(page)))
>  		kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
> +#else
> +	if (!PageSlab(page)) {
> +		u8 tag = random_tag();
> +
> +		kasan_poison_shadow(page_address(page), PAGE_SIZE << order,
> +					tag);
> +		page_kasan_tag_set(page, tag);
> +	}
> +#endif
>  }


diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index b8e0a8215021..f9f2181164a2 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -207,18 +207,11 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
 
 void kasan_alloc_pages(struct page *page, unsigned int order)
 {
-#ifdef CONFIG_KASAN_GENERIC
-	if (likely(!PageHighMem(page)))
-		kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
-#else
-	if (!PageSlab(page)) {
-		u8 tag = random_tag();
+	if (unlikely(PageHighMem(page)))
+		return;
 
-		kasan_poison_shadow(page_address(page), PAGE_SIZE << order,
-					tag);
-		page_kasan_tag_set(page, tag);
-	}
-#endif
+	page_kasan_tag_set(page, random_tag());
+	kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 }
 
 void kasan_free_pages(struct page *page, unsigned int order)
-- 
2.16.1


>  
>  void kasan_free_pages(struct page *page, unsigned int order)
> @@ -433,6 +443,7 @@ void *kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
>  #else
>  	tag = random_tag();
>  	kasan_poison_shadow(ptr, redzone_start - (unsigned long)ptr, tag);
> +	page_kasan_tag_set(page, tag);

As already said before no changes needed in kasan_kmalloc_large. kasan_alloc_pages() alredy did tag_set().

>  #endif
>  	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
>  		KASAN_PAGE_REDZONE);
> @@ -462,7 +473,7 @@ 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;
>  		}
> @@ -475,7 +486,7 @@ 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. */
>  }

Re: [PATCH v1 15/16] khwasan, mm, arm64: tag non slab memory allocated via pagealloc

[Andrey Konovalov]

On Tue, May 15, 2018 at 4:06 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
> You could avoid 'if (!PageSlab())' check by adding page_kasan_tag_reset() into kasan_poison_slab().

>> @@ -526,6 +526,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>>       }
>>
>>       trace_cma_alloc(pfn, page, count, align);
>> +     page_kasan_tag_reset(page);
>
>
> Why? Comment needed.

> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index b8e0a8215021..f9f2181164a2 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -207,18 +207,11 @@ void kasan_unpoison_stack_above_sp_to(const void *watermark)
>
>  void kasan_alloc_pages(struct page *page, unsigned int order)
>  {
> -#ifdef CONFIG_KASAN_GENERIC
> -       if (likely(!PageHighMem(page)))
> -               kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
> -#else
> -       if (!PageSlab(page)) {
> -               u8 tag = random_tag();
> +       if (unlikely(PageHighMem(page)))
> +               return;
>
> -               kasan_poison_shadow(page_address(page), PAGE_SIZE << order,
> -                                       tag);
> -               page_kasan_tag_set(page, tag);
> -       }
> -#endif
> +       page_kasan_tag_set(page, random_tag());
> +       kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
>  }
>
>  void kasan_free_pages(struct page *page, unsigned int order)

> As already said before no changes needed in kasan_kmalloc_large. kasan_alloc_pages() alredy did tag_set().

Will fix all in v2, thanks!

[PATCH v1 16/16] khwasan: update kasan documentation

[Andrey Konovalov]

This patch updates KASAN documentation to reflect the addition of KHWASAN.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 Documentation/dev-tools/kasan.rst | 213 +++++++++++++++++-------------
 1 file changed, 123 insertions(+), 90 deletions(-)

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index f7a18f274357..2e5f1cf766f3 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -8,11 +8,19 @@ 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.
 
-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 has two modes: classic KASAN (a classic version, similar to user space
+ASan) and KHWASAN (a version based on memory tagging, similar to user space
+HWASan).
 
-Currently KASAN is supported only for the x86_64 and arm64 architectures.
+KASAN uses compile-time instrumentation to insert validity checks before every
+memory access, and therefore requires a compiler version that supports that.
+For classic KASAN you need GCC version 4.9.2 or later. GCC 5.0 or later is
+required for detection of out-of-bounds accesses on stack and global variables.
+KHWASAN in turns is only suppoeted in clang and requires revision 330044 or
+later.
+
+Currently classic KASAN is supported for the x86_64, arm64 and xtensa
+architectures, and KHWASAN is supported only for arm64.
 
 Usage
 -----
@@ -21,12 +29,14 @@ 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
+and choose between CONFIG_KASAN_GENERIC (to enable classic KASAN) and
+CONFIG_KASAN_HW (to enabled KHWASAN). You also need to choose 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. For classic KASAN inline instrumentation requires GCC
 version 5.0 or later.
 
-KASAN works with both SLUB and SLAB memory allocators.
+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 +53,80 @@ 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 classic 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 ffff8800696f3d3b by task insmod/2734
+    
+    CPU: 0 PID: 2734 Comm: insmod Not tainted 4.15.0+ #98
+    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 lib/dump_stack.c:17
+     dump_stack+0x83/0xbc lib/dump_stack.c:53
+     print_address_description+0x73/0x280 mm/kasan/report.c:254
+     kasan_report_error mm/kasan/report.c:352
+     kasan_report+0x10e/0x220 mm/kasan/report.c:410
+     __asan_report_store1_noabort+0x17/0x20 mm/kasan/report.c:505
+     kmalloc_oob_right+0xa8/0xbc [test_kasan] lib/test_kasan.c:42
+     kmalloc_tests_init+0x16/0x769 [test_kasan]
+     do_one_initcall+0x9e/0x240 init/main.c:832
+     do_init_module+0x1b6/0x542 kernel/module.c:3462
+     load_module+0x6042/0x9030 kernel/module.c:3786
+     SYSC_init_module+0x18f/0x1c0 kernel/module.c:3858
+     SyS_init_module+0x9/0x10 kernel/module.c:3841
+     do_syscall_64+0x198/0x480 arch/x86/entry/common.c:287
+     entry_SYSCALL_64_after_hwframe+0x21/0x86 arch/x86/entry/entry_64.S:251
+    RIP: 0033:0x7fdd79df99da
+    RSP: 002b:00007fff2229bdf8 EFLAGS: 00000202 ORIG_RAX: 00000000000000af
+    RAX: ffffffffffffffda RBX: 000055c408121190 RCX: 00007fdd79df99da
+    RDX: 00007fdd7a0b8f88 RSI: 0000000000055670 RDI: 00007fdd7a47e000
+    RBP: 000055c4081200b0 R08: 0000000000000003 R09: 0000000000000000
+    R10: 00007fdd79df5d0a R11: 0000000000000202 R12: 00007fdd7a0b8f88
+    R13: 000055c408120090 R14: 0000000000000000 R15: 0000000000000000
+    
+    Allocated by task 2734:
+     save_stack+0x43/0xd0 mm/kasan/common.c:176
+     set_track+0x20/0x30 mm/kasan/common.c:188
+     kasan_kmalloc+0x9a/0xc0 mm/kasan/kasan.c:372
+     kmem_cache_alloc_trace+0xcd/0x1a0 mm/slub.c:2761
+     kmalloc ./include/linux/slab.h:512
+     kmalloc_oob_right+0x56/0xbc [test_kasan] lib/test_kasan.c:36
+     kmalloc_tests_init+0x16/0x769 [test_kasan]
+     do_one_initcall+0x9e/0x240 init/main.c:832
+     do_init_module+0x1b6/0x542 kernel/module.c:3462
+     load_module+0x6042/0x9030 kernel/module.c:3786
+     SYSC_init_module+0x18f/0x1c0 kernel/module.c:3858
+     SyS_init_module+0x9/0x10 kernel/module.c:3841
+     do_syscall_64+0x198/0x480 arch/x86/entry/common.c:287
+     entry_SYSCALL_64_after_hwframe+0x21/0x86 arch/x86/entry/entry_64.S:251
+    
+    The buggy address belongs to the object at ffff8800696f3cc0
+     which belongs to the cache kmalloc-128 of size 128
+    The buggy address is located 123 bytes inside of
+     128-byte region [ffff8800696f3cc0, ffff8800696f3d40)
+    The buggy address belongs to the page:
+    page:ffffea0001a5bcc0 count:1 mapcount:0 mapping:          (null) index:0x0
+    flags: 0x100000000000100(slab)
+    raw: 0100000000000100 0000000000000000 0000000000000000 0000000180150015
+    raw: ffffea0001a8ce40 0000000300000003 ffff88006d001640 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
+     ffff8800696f3c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc
+     ffff8800696f3c80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
+    >ffff8800696f3d00: 00 00 00 00 00 00 00 03 fc fc fc fc fc fc fc fc
+                                            ^
+     ffff8800696f3d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
+     ffff8800696f3e00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
     ==================================================================
 
-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.txt 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 +143,24 @@ 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 KHWASAN this last report section shows the memory tags around the accessed
+address (see Implementation details section).
+
 
 Implementation details
 ----------------------
 
+Classic 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.
+Classic 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 +173,34 @@ 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 accesses 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.
+
+KHWASAN
+~~~~~~~
+
+KHWASAN uses the Top Byte Ignore (TBI) feature of modern arm64 CPUs to store
+a pointer tag in the top byte of kernel pointers. KHWASAN also 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 KHWASAN generates a random tag, tags allocated memory
+with this tag, and embeds this tag into the returned pointer. KHWASAN 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
+ofthe pointer that is used to access this memory. In case of a tag mismatch
+KHWASAN prints a bug report.
+
+KHWASAN 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 KHWASAN reports.
-- 
2.17.0.441.gb46fe60e1d-goog

Re: [PATCH v1 16/16] khwasan: update kasan documentation

[Mike Rapoport]

On Tue, May 08, 2018 at 07:21:02PM +0200, Andrey Konovalov wrote:
> This patch updates KASAN documentation to reflect the addition of KHWASAN.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
>  Documentation/dev-tools/kasan.rst | 213 +++++++++++++++++-------------
>  1 file changed, 123 insertions(+), 90 deletions(-)
> 
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index f7a18f274357..2e5f1cf766f3 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -8,11 +8,19 @@ 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.
> 
> -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 has two modes: classic KASAN (a classic version, similar to user space
> +ASan) and KHWASAN (a version based on memory tagging, similar to user space
> +HWASan).
> 
> -Currently KASAN is supported only for the x86_64 and arm64 architectures.
> +KASAN uses compile-time instrumentation to insert validity checks before every
> +memory access, and therefore requires a compiler version that supports that.
> +For classic KASAN you need GCC version 4.9.2 or later. GCC 5.0 or later is
> +required for detection of out-of-bounds accesses on stack and global variables.
> +KHWASAN in turns is only suppoeted in clang and requires revision 330044 or

Typos: in turn is only supported

> +later.
> +
> +Currently classic KASAN is supported for the x86_64, arm64 and xtensa
> +architectures, and KHWASAN is supported only for arm64.
> 
>  Usage
>  -----
> @@ -21,12 +29,14 @@ 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
> +and choose between CONFIG_KASAN_GENERIC (to enable classic KASAN) and
> +CONFIG_KASAN_HW (to enabled KHWASAN). You also need to choose 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. For classic KASAN inline instrumentation requires GCC
>  version 5.0 or later.
> 
> -KASAN works with both SLUB and SLAB memory allocators.
> +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 +53,80 @@ 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 classic 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 ffff8800696f3d3b by task insmod/2734
> +    
> +    CPU: 0 PID: 2734 Comm: insmod Not tainted 4.15.0+ #98
> +    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 lib/dump_stack.c:17
> +     dump_stack+0x83/0xbc lib/dump_stack.c:53
> +     print_address_description+0x73/0x280 mm/kasan/report.c:254
> +     kasan_report_error mm/kasan/report.c:352
> +     kasan_report+0x10e/0x220 mm/kasan/report.c:410
> +     __asan_report_store1_noabort+0x17/0x20 mm/kasan/report.c:505
> +     kmalloc_oob_right+0xa8/0xbc [test_kasan] lib/test_kasan.c:42
> +     kmalloc_tests_init+0x16/0x769 [test_kasan]
> +     do_one_initcall+0x9e/0x240 init/main.c:832
> +     do_init_module+0x1b6/0x542 kernel/module.c:3462
> +     load_module+0x6042/0x9030 kernel/module.c:3786
> +     SYSC_init_module+0x18f/0x1c0 kernel/module.c:3858
> +     SyS_init_module+0x9/0x10 kernel/module.c:3841
> +     do_syscall_64+0x198/0x480 arch/x86/entry/common.c:287
> +     entry_SYSCALL_64_after_hwframe+0x21/0x86 arch/x86/entry/entry_64.S:251
> +    RIP: 0033:0x7fdd79df99da
> +    RSP: 002b:00007fff2229bdf8 EFLAGS: 00000202 ORIG_RAX: 00000000000000af
> +    RAX: ffffffffffffffda RBX: 000055c408121190 RCX: 00007fdd79df99da
> +    RDX: 00007fdd7a0b8f88 RSI: 0000000000055670 RDI: 00007fdd7a47e000
> +    RBP: 000055c4081200b0 R08: 0000000000000003 R09: 0000000000000000
> +    R10: 00007fdd79df5d0a R11: 0000000000000202 R12: 00007fdd7a0b8f88
> +    R13: 000055c408120090 R14: 0000000000000000 R15: 0000000000000000
> +    
> +    Allocated by task 2734:
> +     save_stack+0x43/0xd0 mm/kasan/common.c:176
> +     set_track+0x20/0x30 mm/kasan/common.c:188
> +     kasan_kmalloc+0x9a/0xc0 mm/kasan/kasan.c:372
> +     kmem_cache_alloc_trace+0xcd/0x1a0 mm/slub.c:2761
> +     kmalloc ./include/linux/slab.h:512
> +     kmalloc_oob_right+0x56/0xbc [test_kasan] lib/test_kasan.c:36
> +     kmalloc_tests_init+0x16/0x769 [test_kasan]
> +     do_one_initcall+0x9e/0x240 init/main.c:832
> +     do_init_module+0x1b6/0x542 kernel/module.c:3462
> +     load_module+0x6042/0x9030 kernel/module.c:3786
> +     SYSC_init_module+0x18f/0x1c0 kernel/module.c:3858
> +     SyS_init_module+0x9/0x10 kernel/module.c:3841
> +     do_syscall_64+0x198/0x480 arch/x86/entry/common.c:287
> +     entry_SYSCALL_64_after_hwframe+0x21/0x86 arch/x86/entry/entry_64.S:251
> +    
> +    The buggy address belongs to the object at ffff8800696f3cc0
> +     which belongs to the cache kmalloc-128 of size 128
> +    The buggy address is located 123 bytes inside of
> +     128-byte region [ffff8800696f3cc0, ffff8800696f3d40)
> +    The buggy address belongs to the page:
> +    page:ffffea0001a5bcc0 count:1 mapcount:0 mapping:          (null) index:0x0
> +    flags: 0x100000000000100(slab)
> +    raw: 0100000000000100 0000000000000000 0000000000000000 0000000180150015
> +    raw: ffffea0001a8ce40 0000000300000003 ffff88006d001640 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
> +     ffff8800696f3c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc
> +     ffff8800696f3c80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
> +    >ffff8800696f3d00: 00 00 00 00 00 00 00 03 fc fc fc fc fc fc fc fc
> +                                            ^
> +     ffff8800696f3d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
> +     ffff8800696f3e00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>      ==================================================================
> 
> -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.txt 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 +143,24 @@ 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 KHWASAN this last report section shows the memory tags around the accessed
> +address (see Implementation details section).
> +
> 
>  Implementation details
>  ----------------------
> 
> +Classic 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.
> +Classic 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 +173,34 @@ 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 accesses 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.
> +
> +KHWASAN
> +~~~~~~~
> +
> +KHWASAN uses the Top Byte Ignore (TBI) feature of modern arm64 CPUs to store
> +a pointer tag in the top byte of kernel pointers. KHWASAN also 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 KHWASAN generates a random tag, tags allocated memory
> +with this tag, and embeds this tag into the returned pointer. KHWASAN 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
> +ofthe pointer that is used to access this memory. In case of a tag mismatch

of the

> +KHWASAN prints a bug report.
> +
> +KHWASAN 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 KHWASAN reports.
> -- 
> 2.17.0.441.gb46fe60e1d-goog
> 

-- 
Sincerely yours,
Mike.

Re: [PATCH v1 16/16] khwasan: update kasan documentation

[Andrey Konovalov]

On Wed, May 9, 2018 at 7:26 AM, Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
>
> Typos: in turn is only supported
>
> of the
>

Hi Mike!

Will fix both in v2.

Thanks!