* [PATCH 0/4] kasan: support stack instrumentation for tag-based mode
@ 2020-07-31 13:20 Andrey Konovalov
2020-07-31 13:20 ` [PATCH 1/4] kasan: don't tag stacks allocated with pagealloc Andrey Konovalov
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Andrey Konovalov @ 2020-07-31 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov, Marco Elver,
kasan-dev, linux-mm, linux-kernel, Walter Wu, Elena Petrova,
Vincenzo Frascino, Catalin Marinas, Andrey Konovalov
This goes on top of Walter's patch titled "kasan: fix KASAN unit tests
for tag-based KASAN" (already in mm tree).
Bugzilla link: https://bugzilla.kernel.org/show_bug.cgi?id=203497
Thanks to Walter Wu for debugging and testing.
Andrey Konovalov (4):
kasan: don't tag stacks allocated with pagealloc
kasan, arm64: don't instrument functions that enable kasan
kasan: allow enabling stack tagging for tag-based mode
kasan: adjust kasan_stack_oob for tag-based mode
arch/arm64/kernel/setup.c | 2 +-
init/main.c | 2 +-
kernel/fork.c | 3 ++-
lib/test_kasan.c | 2 +-
scripts/Makefile.kasan | 3 ++-
5 files changed, 7 insertions(+), 5 deletions(-)
--
2.28.0.163.g6104cc2f0b6-goog
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 1/4] kasan: don't tag stacks allocated with pagealloc
2020-07-31 13:20 [PATCH 0/4] kasan: support stack instrumentation for tag-based mode Andrey Konovalov
@ 2020-07-31 13:20 ` Andrey Konovalov
2020-07-31 13:20 ` [PATCH 2/4] kasan, arm64: don't instrument functions that enable kasan Andrey Konovalov
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Andrey Konovalov @ 2020-07-31 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov, Marco Elver,
kasan-dev, linux-mm, linux-kernel, Walter Wu, Elena Petrova,
Vincenzo Frascino, Catalin Marinas, Andrey Konovalov
This patch prepares Software Tag-Based KASAN for stack tagging support.
With Tag-Based KASAN when kernel stacks are allocated via pagealloc
(which happens when CONFIG_VMAP_STACK is not enabled), they get tagged.
KASAN instrumentation doesn't expect the sp register to be tagged, and
this leads to false-positive reports.
Fix by resetting the tag of kernel stack pointers after allocation.
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
kernel/fork.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index d03c9586d342..9cea2265e677 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -261,7 +261,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
THREAD_SIZE_ORDER);
if (likely(page)) {
- tsk->stack = page_address(page);
+ tsk->stack = kasan_reset_tag(page_address(page));
return tsk->stack;
}
return NULL;
@@ -302,6 +302,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
{
unsigned long *stack;
stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node);
+ stack = kasan_reset_tag(stack);
tsk->stack = stack;
return stack;
}
--
2.28.0.163.g6104cc2f0b6-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/4] kasan, arm64: don't instrument functions that enable kasan
2020-07-31 13:20 [PATCH 0/4] kasan: support stack instrumentation for tag-based mode Andrey Konovalov
2020-07-31 13:20 ` [PATCH 1/4] kasan: don't tag stacks allocated with pagealloc Andrey Konovalov
@ 2020-07-31 13:20 ` Andrey Konovalov
2020-07-31 14:21 ` Catalin Marinas
2020-07-31 13:20 ` [PATCH 3/4] kasan: allow enabling stack tagging for tag-based mode Andrey Konovalov
2020-07-31 13:20 ` [PATCH 4/4] kasan: adjust kasan_stack_oob " Andrey Konovalov
3 siblings, 1 reply; 6+ messages in thread
From: Andrey Konovalov @ 2020-07-31 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov, Marco Elver,
kasan-dev, linux-mm, linux-kernel, Walter Wu, Elena Petrova,
Vincenzo Frascino, Catalin Marinas, Andrey Konovalov
This patch prepares Software Tag-Based KASAN for stack tagging support.
With stack tagging enabled, KASAN tags stack variable in each function
in its prologue. In start_kernel() stack variables get tagged before KASAN
is enabled via setup_arch()->kasan_init(). As the result the tags for
start_kernel()'s stack variables end up in the temporary shadow memory.
Later when KASAN gets enabled, switched to normal shadow, and starts
checking tags, this leads to false-positive reports, as proper tags are
missing in normal shadow.
Disable KASAN instrumentation for start_kernel(). Also disable it for
arm64's setup_arch() as a precaution (it doesn't have any stack variables
right now).
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
arch/arm64/kernel/setup.c | 2 +-
init/main.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index c793276ec7ad..87e81d29e6fb 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -276,7 +276,7 @@ arch_initcall(reserve_memblock_reserved_regions);
u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
-void __init setup_arch(char **cmdline_p)
+void __init __no_sanitize_address setup_arch(char **cmdline_p)
{
init_mm.start_code = (unsigned long) _text;
init_mm.end_code = (unsigned long) _etext;
diff --git a/init/main.c b/init/main.c
index 2d74985e09b1..c73a16ff213e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -829,7 +829,7 @@ void __init __weak arch_call_rest_init(void)
rest_init();
}
-asmlinkage __visible void __init start_kernel(void)
+asmlinkage __visible __no_sanitize_address void __init start_kernel(void)
{
char *command_line;
char *after_dashes;
--
2.28.0.163.g6104cc2f0b6-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 3/4] kasan: allow enabling stack tagging for tag-based mode
2020-07-31 13:20 [PATCH 0/4] kasan: support stack instrumentation for tag-based mode Andrey Konovalov
2020-07-31 13:20 ` [PATCH 1/4] kasan: don't tag stacks allocated with pagealloc Andrey Konovalov
2020-07-31 13:20 ` [PATCH 2/4] kasan, arm64: don't instrument functions that enable kasan Andrey Konovalov
@ 2020-07-31 13:20 ` Andrey Konovalov
2020-07-31 13:20 ` [PATCH 4/4] kasan: adjust kasan_stack_oob " Andrey Konovalov
3 siblings, 0 replies; 6+ messages in thread
From: Andrey Konovalov @ 2020-07-31 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov, Marco Elver,
kasan-dev, linux-mm, linux-kernel, Walter Wu, Elena Petrova,
Vincenzo Frascino, Catalin Marinas, Andrey Konovalov
Use CONFIG_KASAN_STACK to enable stack tagging.
Note, that HWASAN short granules [1] are disabled. Supporting those will
require more kernel changes.
[1] https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
scripts/Makefile.kasan | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 03757cc60e06..f4beee1b0013 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -44,7 +44,8 @@ else
endif
CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
- -mllvm -hwasan-instrument-stack=0 \
+ -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
+ -mllvm -hwasan-use-short-granules=0 \
$(instrumentation_flags)
endif # CONFIG_KASAN_SW_TAGS
--
2.28.0.163.g6104cc2f0b6-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 4/4] kasan: adjust kasan_stack_oob for tag-based mode
2020-07-31 13:20 [PATCH 0/4] kasan: support stack instrumentation for tag-based mode Andrey Konovalov
` (2 preceding siblings ...)
2020-07-31 13:20 ` [PATCH 3/4] kasan: allow enabling stack tagging for tag-based mode Andrey Konovalov
@ 2020-07-31 13:20 ` Andrey Konovalov
3 siblings, 0 replies; 6+ messages in thread
From: Andrey Konovalov @ 2020-07-31 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov, Marco Elver,
kasan-dev, linux-mm, linux-kernel, Walter Wu, Elena Petrova,
Vincenzo Frascino, Catalin Marinas, Andrey Konovalov
Use OOB_TAG_OFF as access offset to land the access into the next granule.
Suggested-by: Walter Wu <walter-zh.wu@mediatek.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
lib/test_kasan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index f362f2662938..53e953bb1d1d 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -488,7 +488,7 @@ static noinline void __init kasan_global_oob(void)
static noinline void __init kasan_stack_oob(void)
{
char stack_array[10];
- volatile int i = 0;
+ volatile int i = OOB_TAG_OFF;
char *p = &stack_array[ARRAY_SIZE(stack_array) + i];
pr_info("out-of-bounds on stack\n");
--
2.28.0.163.g6104cc2f0b6-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 2/4] kasan, arm64: don't instrument functions that enable kasan
2020-07-31 13:20 ` [PATCH 2/4] kasan, arm64: don't instrument functions that enable kasan Andrey Konovalov
@ 2020-07-31 14:21 ` Catalin Marinas
0 siblings, 0 replies; 6+ messages in thread
From: Catalin Marinas @ 2020-07-31 14:21 UTC (permalink / raw)
To: Andrey Konovalov
Cc: Andrew Morton, Andrey Ryabinin, Alexander Potapenko,
Dmitry Vyukov, Marco Elver, kasan-dev, linux-mm, linux-kernel,
Walter Wu, Elena Petrova, Vincenzo Frascino
On Fri, Jul 31, 2020 at 03:20:39PM +0200, Andrey Konovalov wrote:
> This patch prepares Software Tag-Based KASAN for stack tagging support.
>
> With stack tagging enabled, KASAN tags stack variable in each function
> in its prologue. In start_kernel() stack variables get tagged before KASAN
> is enabled via setup_arch()->kasan_init(). As the result the tags for
> start_kernel()'s stack variables end up in the temporary shadow memory.
> Later when KASAN gets enabled, switched to normal shadow, and starts
> checking tags, this leads to false-positive reports, as proper tags are
> missing in normal shadow.
>
> Disable KASAN instrumentation for start_kernel(). Also disable it for
> arm64's setup_arch() as a precaution (it doesn't have any stack variables
> right now).
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
For arm64:
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-07-31 14:21 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2020-07-31 13:20 [PATCH 0/4] kasan: support stack instrumentation for tag-based mode Andrey Konovalov
2020-07-31 13:20 ` [PATCH 1/4] kasan: don't tag stacks allocated with pagealloc Andrey Konovalov
2020-07-31 13:20 ` [PATCH 2/4] kasan, arm64: don't instrument functions that enable kasan Andrey Konovalov
2020-07-31 14:21 ` Catalin Marinas
2020-07-31 13:20 ` [PATCH 3/4] kasan: allow enabling stack tagging for tag-based mode Andrey Konovalov
2020-07-31 13:20 ` [PATCH 4/4] kasan: adjust kasan_stack_oob " Andrey Konovalov
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