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Date: Fri, 26 Apr 2024 11:16:22 +0200
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Message-ID: <20240426091622.3846771-1-glider@google.com>
Subject: [PATCH v2] kmsan: compiler_types: declare __no_sanitize_or_inline
From: Alexander Potapenko <glider@google.com>
To: glider@google.com
Cc: elver@google.com, dvyukov@google.com, akpm@linux-foundation.org, 
	ojeda@kernel.org, linux-kernel@vger.kernel.org, 
	syzbot+355c5bb8c1445c871ee8@syzkaller.appspotmail.com, stable@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

It turned out that KMSAN instruments READ_ONCE_NOCHECK(), resulting in
false positive reports, because __no_sanitize_or_inline enforced inlining.

Properly declare __no_sanitize_or_inline under __SANITIZE_MEMORY__,
so that it does not __always_inline the annotated function.

Reported-by: syzbot+355c5bb8c1445c871ee8@syzkaller.appspotmail.com
Link: https://lkml.kernel.org/r/000000000000826ac1061675b0e3@google.com
Fixes: 5de0ce85f5a4 ("kmsan: mark noinstr as __no_sanitize_memory")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco Elver <elver@google.com>
---
 include/linux/compiler_types.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 0caf354cb94b5..a6a28952836cb 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -278,6 +278,17 @@ struct ftrace_likely_data {
 # define __no_kcsan
 #endif
 
+#ifdef __SANITIZE_MEMORY__
+/*
+ * Similarly to KASAN and KCSAN, KMSAN loses function attributes of inlined
+ * functions, therefore disabling KMSAN checks also requires disabling inlining.
+ *
+ * __no_sanitize_or_inline effectively prevents KMSAN from reporting errors
+ * within the function and marks all its outputs as initialized.
+ */
+# define __no_sanitize_or_inline __no_kmsan_checks notrace __maybe_unused
+#endif
+
 #ifndef __no_sanitize_or_inline
 #define __no_sanitize_or_inline __always_inline
 #endif
-- 
2.44.0.769.g3c40516874-goog