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[195.92.253.2]) by mx.google.com with ESMTPS id i7si4649849wrp.46.2019.03.11.21.08.58 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Mar 2019 21:08:58 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of viro@ftp.linux.org.uk designates 195.92.253.2 as permitted sender) client-ip=195.92.253.2; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of viro@ftp.linux.org.uk designates 195.92.253.2 as permitted sender) smtp.mailfrom=viro@ftp.linux.org.uk Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1h3YiL-0003ts-SD; Tue, 12 Mar 2019 04:08:30 +0000 Date: Tue, 12 Mar 2019 04:08:29 +0000 From: Al Viro To: syzbot Cc: airlied@linux.ie, akpm@linux-foundation.org, amir73il@gmail.com, chris@chris-wilson.co.uk, darrick.wong@oracle.com, david@fromorbit.com, dri-devel@lists.freedesktop.org, dvyukov@google.com, eparis@redhat.com, hannes@cmpxchg.org, hughd@google.com, intel-gfx@lists.freedesktop.org, jack@suse.cz, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, jrdr.linux@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, mszeredi@redhat.com, penguin-kernel@i-love.sakura.ne.jp, peterz@infradead.org, rodrigo.vivi@intel.com, syzkaller-bugs@googlegroups.com, willy@infradead.org Subject: Re: INFO: rcu detected stall in sys_sendfile64 (2) Message-ID: <20190312040829.GQ2217@ZenIV.linux.org.uk> References: <00000000000010b2fc057fcdfaba@google.com> <0000000000008c75b50583ddb5f8@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000008c75b50583ddb5f8@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Mon, Mar 11, 2019 at 08:59:00PM -0700, syzbot wrote: > syzbot has bisected this bug to: > > commit 34e07e42c55aeaa78e93b057a6664e2ecde3fadb > Author: Chris Wilson > Date: Thu Feb 8 10:54:48 2018 +0000 > > drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13220283200000 > start commit: 34e07e42 drm/i915: Add missing kerneldoc for 'ent' in i915.. > git tree: upstream > final crash: https://syzkaller.appspot.com/x/report.txt?x=10a20283200000 > console output: https://syzkaller.appspot.com/x/log.txt?x=17220283200000 > kernel config: https://syzkaller.appspot.com/x/.config?x=abc3dc9b7a900258 > dashboard link: https://syzkaller.appspot.com/bug?extid=1505c80c74256c6118a5 > userspace arch: amd64 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12c4dc28c00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15df4108c00000 > > Reported-by: syzbot+1505c80c74256c6118a5@syzkaller.appspotmail.com > Fixes: 34e07e42 ("drm/i915: Add missing kerneldoc for 'ent' in > i915_driver_init_early") Umm... Might be a good idea to add some plausibility filters - it is, in theory, possible that adding a line in a comment changes behaviour (without compiler bugs, even - playing with __LINE__ is all it would take), but the odds that it's _not_ a false positive are very low.