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Fri, 27 Dec 2019 04:46:14 +0000 (UTC) Received: from ming.t460p (ovpn-8-24.pek2.redhat.com [10.72.8.24]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 82C415D9C5; Fri, 27 Dec 2019 04:46:05 +0000 (UTC) Date: Fri, 27 Dec 2019 12:46:00 +0800 From: Ming Lei To: syzbot Cc: akpm@linux-foundation.org, axboe@kernel.dk, dave@stgolabs.net, hch@lst.de, hughd@google.com, ktkhai@virtuozzo.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, osandov@fb.com, syzkaller-bugs@googlegroups.com Subject: Re: INFO: task hung in sync_inodes_sb (3) Message-ID: <20191227044600.GA9220@ming.t460p> References: <000000000000016d8b059aa2030e@google.com> <0000000000002b326d059aa295e9@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0000000000002b326d059aa295e9@google.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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, Dec 26, 2019 at 02:06:01PM -0800, syzbot wrote: > syzbot has bisected this bug to: > > commit 6dc4f100c175dd0511ae8674786e7c9006cdfbfa > Author: Ming Lei > Date: Fri Feb 15 11:13:19 2019 +0000 > > block: allow bio_for_each_segment_all() to iterate over multi-page bvec > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1674423ee00000 > start commit: 46cf053e Linux 5.5-rc3 > git tree: upstream > final crash: https://syzkaller.appspot.com/x/report.txt?x=1574423ee00000 > console output: https://syzkaller.appspot.com/x/log.txt?x=1174423ee00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ed9d672709340e35 > dashboard link: https://syzkaller.appspot.com/bug?extid=2b9e54155c8c25d8d165 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=152bdc56e00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159c489ee00000 > > Reported-by: syzbot+2b9e54155c8c25d8d165@syzkaller.appspotmail.com > Fixes: 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate > over multi-page bvec") Looks this syzbot test triggers bio truncate(guard_bio_eod()), and the truncated bytes is bigger than the last bvec, which length is overflowed by 'bvec->bv_len -= truncated_bytes'. Finally bio_for_each_segment_all() trigger the issue. Will figure out one patch to fix it. Thanks, Ming