Thread (45 messages) 45 messages, 4 authors, 2022-01-04
STALE1609d REVIEWED: 3 (3M)
Revisions (6)
  1. v1 [diff vs current]
  2. v2 [diff vs current]
  3. v3 [diff vs current]
  4. v4 [diff vs current]
  5. v5 current
  6. v6 [diff vs current]

[PATCH mm v5 23/39] kasan, arm64: reset pointer tags of vmapped stacks

From: <hidden>
Date: 2021-12-30 19:15:19
Also in: linux-mm, lkml
Subsystem: arm64 port (aarch64 architecture), the rest · Maintainers: Catalin Marinas, Will Deacon, Linus Torvalds

From: Andrey Konovalov <redacted>

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.

Signed-off-by: Andrey Konovalov <redacted>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

---

Changes v2->v3:
- Add this patch.
---
 arch/arm64/include/asm/vmap_stack.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/vmap_stack.h b/arch/arm64/include/asm/vmap_stack.h
index 894e031b28d2..20873099c035 100644
--- a/arch/arm64/include/asm/vmap_stack.h
+++ b/arch/arm64/include/asm/vmap_stack.h
@@ -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 */
-- 
2.25.1


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