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[185.231.240.75]) by mx.google.com with ESMTPS id e3si22117627ljg.124.2019.05.23.01.52.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 May 2019 01:52:49 -0700 (PDT) Received-SPF: pass (google.com: domain of aryabinin@virtuozzo.com designates 185.231.240.75 as permitted sender) client-ip=185.231.240.75; Authentication-Results: mx.google.com; spf=pass (google.com: domain of aryabinin@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=aryabinin@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Received: from [172.16.25.12] by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1hTjSu-0000Q9-Mk; Thu, 23 May 2019 11:52:44 +0300 Subject: Re: [PATCH v2] kasan: Initialize tag to 0xff in __kasan_kmalloc To: Andrew Morton Cc: Nathan Chancellor , Alexander Potapenko , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Nick Desaulniers , clang-built-linux@googlegroups.com References: <20190502153538.2326-1-natechancellor@gmail.com> <20190502163057.6603-1-natechancellor@gmail.com> From: Andrey Ryabinin Message-ID: <126d5884-b906-f85b-e893-a6a30ac0082c@virtuozzo.com> Date: Thu, 23 May 2019 11:53:02 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190502163057.6603-1-natechancellor@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 5/2/19 7:30 PM, Nathan Chancellor 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 Fixes: 7f94ffbc4c6a ("kasan: add hooks implementation for tag-based mode") Cc: Reviewed-by: Andrey Ryabinin > --- > > v1 -> v2: > > * Initialize tag to 0xff at Andrey's request > > 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..242fdc01aaa9 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 = 0xff; > > if (gfpflags_allow_blocking(flags)) > quarantine_reduce(); >