Re: [PATCH mm v4 22/39] kasan, fork: reset pointer tags of vmapped stacks
From: Alexander Potapenko <glider@google.com>
Date: 2021-12-21 15:11:54
Also in:
linux-arm-kernel, lkml
On Mon, Dec 20, 2021 at 11:01 PM [off-list ref] wrote:
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>
Reviewed-by: Alexander Potapenko <glider@google.com>
quoted hunk ↗ jump to hunk
--- 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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