Thread (60 messages) 60 messages, 5 authors, 2021-12-30
STALE1637d
Revisions (6)
  1. v1 [diff vs current]
  2. v2 [diff vs current]
  3. v3 [diff vs current]
  4. v4 current
  5. v5 [diff vs current]
  6. v6 [diff vs current]

[PATCH mm v4 22/39] kasan, fork: reset pointer tags of vmapped stacks

From: <hidden>
Date: 2021-12-20 22:01:30
Also in: linux-arm-kernel, lkml
Subsystem: exec & binfmt api, elf, memory management - core, scheduler, the rest · Maintainers: Kees Cook, Andrew Morton, David Hildenbrand, Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot, 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
alloc_thread_stack_node().

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>

---

Changes v2->v3:
- Update patch description.
---
 kernel/fork.c | 1 +
 1 file changed, 1 insertion(+)
diff --git a/kernel/fork.c b/kernel/fork.c
index 403b9dbbfb62..4125373dba4e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -254,6 +254,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 	 * so cache the vm_struct.
 	 */
 	if (stack) {
+		stack = kasan_reset_tag(stack);
 		tsk->stack_vm_area = find_vm_area(stack);
 		tsk->stack = stack;
 	}
-- 
2.25.1

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