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kasan, arm64: reset pointer tags of vmapped stacks

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Once tag-based KASAN modes start tagging vmalloc() allocations, kernel
stacks start getting tagged if CONFIG_VMAP_STACK is enabled.

Reset the tag of kernel stack pointers after allocation in
arch_alloc_vmap_stack().

For SW_TAGS KASAN, when CONFIG_KASAN_STACK is enabled, the instrumentation
can't handle the SP register being tagged.

For HW_TAGS KASAN, there's no instrumentation-related issues.  However,
the impact of having a tagged SP register needs to be properly evaluated,
so keep it non-tagged for now.

Note, that the memory for the stack allocation still gets tagged to catch
vmalloc-into-stack out-of-bounds accesses.

[andreyknvl@google.com: fix case when a stack is retrieved from cached_stacks]
  Link: https://lkml.kernel.org/r/f50c5f96ef896d7936192c888b0c0a7674e33184.1644943792.git.andreyknvl@google.com
[dan.carpenter@oracle.com: remove unnecessary check in alloc_thread_stack_node()]
  Link: https://lkml.kernel.org/r/20220301080706.GB17208@kili

Link: https://lkml.kernel.org/r/698c5ab21743c796d46c15d075b9481825973e34.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marco Elver <elver@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2022-03-24 18:11:10 -07:00 committed by Linus Torvalds
parent c08e6a1206
commit 51fb34de2a
2 changed files with 10 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/arm64/include/asm/vmap_stack.h
View File

@ -17,10 +17,13 @@
*/
static inline unsigned long *arch_alloc_vmap_stack(size_t stack_size, int node)
{
void *p;
BUILD_BUG_ON(!IS_ENABLED(CONFIG_VMAP_STACK));
return __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node,
p = __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node,
__builtin_return_address(0));
return kasan_reset_tag(p);
}
#endif /* __ASM_VMAP_STACK_H */

11
kernel/fork.c
View File

@ -286,11 +286,13 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node)
if (!s)
continue;
/* Mark stack accessible for KASAN. */
/* Reset stack metadata. */
kasan_unpoison_range(s->addr, THREAD_SIZE);
stack = kasan_reset_tag(s->addr);
/* Clear stale pointers from reused stack. */
memset(s->addr, 0, THREAD_SIZE);
memset(stack, 0, THREAD_SIZE);
if (memcg_charge_kernel_stack(s)) {
vfree(s->addr);
@ -298,7 +300,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node)
}
tsk->stack_vm_area = s;
tsk->stack = s->addr;
tsk->stack = stack;
return 0;
}
@ -326,8 +328,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node)
* so cache the vm_struct.
*/
tsk->stack_vm_area = vm;
if (stack)
stack = kasan_reset_tag(stack);
stack = kasan_reset_tag(stack);
tsk->stack = stack;
return 0;
}