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bh=zbIyW6IxeKD2HydxptNfmQ9f408xfblS77FoSfDXhoQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=MfAzS0Dwhw6jr1ddIb38y+X/5DMS0034FSBQ/4BWmnEjXALKeNBFsOuP1E9DPn2c+ L7UJfNTy4zgpD+clLXMLaHu7y12vM1g0Bj6omFkJdN2n/zaA0lbdkRn0VZVAE4VJ4H XMmf4/3zCOJrV8y7MPoDYcrj1hPn+ZK37d+NIe/o= Date: Thu, 15 Dec 2022 13:22:36 -0800 From: Andrew Morton To: Anastasia Belova Cc: Max Filippov , Ingo Molnar , Vineet Gupta , "Russell King (Oracle)" , Geert Uytterhoeven , linux-mm@kvack.org, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org Subject: Re: [PATCH] mm: Add check for NULL for unlocked in fixup_user_fault Message-Id: <20221215132236.195e6f3ac1e1cc4e9e012c8f@linux-foundation.org> In-Reply-To: <20221215093930.22026-1-abelova@astralinux.ru> References: <20221215093930.22026-1-abelova@astralinux.ru> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2B71F140005 X-Stat-Signature: k4j99xaimx7gukbx5qs1w8f6mgf5xst3 X-HE-Tag: 1671139360-984766 X-HE-Meta: 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 7Ol+T2Kw K7WxYWagc3COoBAeD304VfztnrUztxJsst75fPw3FADPNRRQ7b/oq6MHsnvACNCXSP1IktKf3M2VlH2rJUxFCfy27ecCXpIlBO+nyh3KP0dQqCARCP0L9eUODdBGvXRE2Rt/EmxwuIpx5WW4w2r2+5GSOsrCmy4aSK7aWIFQMy5sko2nLA8nAgdeUTtKrLbKW4iWz 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 Thu, 15 Dec 2022 12:39:30 +0300 Anastasia Belova wrote: > Check unlocked for NULL before dereference. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > ... > > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1282,7 +1282,8 @@ int fixup_user_fault(struct mm_struct *mm, > * could tell the callers so they do not need to unlock. > */ > mmap_read_lock(mm); > - *unlocked = true; > + if (unlocked) > + *unlocked = true; > return 0; > } I don't believe this is necessary unless the caller passed FAULT_FLAG_KILLABLE or FAULT_FLAG_ALLOW_RETRY in fault_flags. It's clear as mud and some code comments would help.