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Message-ID: <20221118172305.3321253-1-glider@google.com>
Date: Fri, 18 Nov 2022 18:23:05 +0100
From: Alexander Potapenko <glider@...gle.com>
To: glider@...gle.com
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org,
linux-kernel@...r.kernel.org, Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH] 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.
Link: https://github.com/google/kmsan/issues/89
Link: https://lore.kernel.org/lkml/Y3b9AAEKp2Vr3e6O@sol.localdomain/
Cc: Eric Biggers <ebiggers@...nel.org>
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
arch/x86/include/asm/thread_info.h | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index f0cb881c1d690..f1cccba52eb97 100644
--- 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)
--
2.38.1.584.g0f3c55d4c2-goog
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