x86: Suppress KMSAN reports in arch_within_stack_frames()

arch_within_stack_frames() performs stack walking and may confuse KMSAN by stepping on stale shadow values. To prevent false positive reports, disable KMSAN checks in this function. This fixes KMSAN's interoperability with CONFIG_HARDENED_USERCOPY. Signed-off-by: Alexander Potapenko <[email protected]> Signed-off-by: Dave Hansen <[email protected]> Tested-by: Eric Biggers <[email protected]> Link: google/kmsan#89 Link: https://lore.kernel.org/lkml/[email protected]/ Link: https://lore.kernel.org/all/20221118172305.3321253-1-glider%40google.com
wafgo · Jan 27, 2023 · ce3ba2a · ce3ba2a
1 parent 6be9a8f
commit ce3ba2a
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
@@ -163,7 +163,12 @@ struct thread_info {
  *	GOOD_FRAME	if within a frame
  *	BAD_STACK	if placed across a frame boundary (or outside stack)
  *	NOT_STACK	unable to determine (no frame pointers, etc)
+ *
+ * This function reads pointers from the stack and dereferences them. The
+ * pointers may not have their KMSAN shadow set up properly, which may result
+ * in false positive reports. Disable instrumentation to avoid those.
  */
+__no_kmsan_checks
 static inline int arch_within_stack_frames(const void * const stack,
 					   const void * const stackend,
 					   const void *obj, unsigned long len)