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[146.241.102.46]) by smtp.gmail.com with ESMTPSA id m4sm6559554wml.28.2021.09.22.08.13.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Sep 2021 08:13:43 -0700 (PDT) Message-ID: <89d72aca4e30335a03322612cf164420be11d8eb.camel@redhat.com> Subject: Re: [syzbot] INFO: rcu detected stall in sys_recvmmsg From: Paolo Abeni To: syzbot , axboe@kernel.dk, christian.brauner@ubuntu.com, davem@davemloft.net, dkadashev@gmail.com, kuba@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mathew.j.martineau@linux.intel.com, matthieu.baerts@tessares.net, mptcp@lists.linux.dev, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk Date: Wed, 22 Sep 2021 17:13:42 +0200 In-Reply-To: <0000000000003216d705cc8a62d6@google.com> References: <0000000000003216d705cc8a62d6@google.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, 2021-09-21 at 17:13 -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 1f77990c4b79 Add linux-next specific files for 20210920 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=1383891d300000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ab1346371f2e6884 > dashboard link: https://syzkaller.appspot.com/bug?extid=3360da629681aa0d22fe > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1625f1ab300000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17eb1b3b300000 > > The issue was bisected to: > > commit 020250f31c4c75ac7687a673e29c00786582a5f4 > Author: Dmitry Kadashev > Date: Thu Jul 8 06:34:43 2021 +0000 > > namei: make do_linkat() take struct filename > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15f5ef77300000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=17f5ef77300000 > console output: https://syzkaller.appspot.com/x/log.txt?x=13f5ef77300000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+3360da629681aa0d22fe@syzkaller.appspotmail.com > Fixes: 020250f31c4c ("namei: make do_linkat() take struct filename") I'm unsure why the bisection points to this commit. This looks like an MPTCP specific issue, due to bad handling of MSG_WAITALL recvmsg() flag. I'll test a fix with syzbot to confirm the above. Cheers, Paolo