| From | andrey.konovalov@linux ... | Subject | [PATCH v2 22/34] kasan, fork: don't tag stacks allocated with vmalloc | Date | Mon, 6 Dec 2021 22:43:59 +0100 |
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From: Andrey Konovalov <andreyknvl@google.com>
Once tag-based KASAN modes start tagging vmalloc() allocations, kernel stacks will start getting tagged if CONFIG_VMAP_STACK is enabled.
Reset the tag of kernel stack pointers after allocation.
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 pointer 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 <andreyknvl@google.com> --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/fork.c b/kernel/fork.c index 3244cc56b697..062d1484ef42 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -253,6 +253,7 @@ 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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