From: Nathan Chancellor <natechancellor@gmail.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>
Cc: kasan-dev@googlegroups.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Nick Desaulniers <ndesaulniers@google.com>,
clang-built-linux@googlegroups.com,
Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH] kasan: Zero initialize tag in __kasan_kmalloc
Date: Thu, 2 May 2019 08:35:38 -0700 [thread overview]
Message-ID: <20190502153538.2326-1-natechancellor@gmail.com> (raw)
When building with -Wuninitialized and CONFIG_KASAN_SW_TAGS unset, Clang
warns:
mm/kasan/common.c:484:40: warning: variable 'tag' is uninitialized when
used here [-Wuninitialized]
kasan_unpoison_shadow(set_tag(object, tag), size);
^~~
set_tag ignores tag in this configuration but clang doesn't realize it
at this point in its pipeline, as it points to arch_kasan_set_tag as
being the point where it is used, which will later be expanded to
(void *)(object) without a use of tag. Just zero initialize tag, as it
removes this warning and doesn't change the meaning of the code.
Link: https://github.com/ClangBuiltLinux/linux/issues/465
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
mm/kasan/common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 36afcf64e016..4c5af68f2a8b 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -464,7 +464,7 @@ static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
{
unsigned long redzone_start;
unsigned long redzone_end;
- u8 tag;
+ u8 tag = 0;
if (gfpflags_allow_blocking(flags))
quarantine_reduce();
--
2.21.0
next reply other threads:[~2019-05-02 15:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-02 15:35 Nathan Chancellor [this message]
2019-05-02 16:24 ` [PATCH] kasan: Zero initialize tag in __kasan_kmalloc Andrey Konovalov
2019-05-02 16:30 ` [PATCH v2] kasan: Initialize tag to 0xff " Nathan Chancellor
2019-05-02 16:40 ` Andrey Konovalov
2019-05-23 1:47 ` Nathan Chancellor
2019-05-23 8:53 ` Andrey Ryabinin
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