diff mbox series

[v2,22/34] kasan, fork: don't tag stacks allocated with vmalloc

Message ID 92424a5bd4ceaabe6412da558624f2340d107756.1638825394.git.andreyknvl@google.com (mailing list archive)
State New, archived
Headers show
Series kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW_TAGS | expand

Commit Message

andrey.konovalov@linux.dev Dec. 6, 2021, 9:43 p.m. UTC 
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 mbox series

Patch

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;
 	}