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From: Nathan Chancellor <natechancellor@gmail.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Linux Memory Management List <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com
Subject: Re: [PATCH v2] kasan: Initialize tag to 0xff in __kasan_kmalloc
Date: Wed, 22 May 2019 18:47:32 -0700	[thread overview]
Message-ID: <20190523014732.GA17640@archlinux-epyc> (raw)
In-Reply-To: <CAAeHK+wzuSKhTE6hjph1SXCUwH8TEd1C+J0cAQN=pRvKw+Wh_w@mail.gmail.com>

On Thu, May 02, 2019 at 06:40:52PM +0200, Andrey Konovalov wrote:
> On Thu, May 2, 2019 at 6:31 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > 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. Initialize tag to 0xff, 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>
> 
> Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
> 
> Thanks!
> 

Thanks Andrey! Did anyone else have any other comments or can this be
picked up?

Cheers,
Nathan

  reply	other threads:[~2019-05-23  1:47 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-02 15:35 [PATCH] kasan: Zero initialize tag " Nathan Chancellor
2019-05-02 16:24 ` 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 [this message]
2019-05-23  8:53   ` Andrey Ryabinin

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