From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-io1-f67.google.com (mail-io1-f67.google.com [209.85.166.67]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 142673FC7 for ; Wed, 22 Sep 2021 15:15:48 +0000 (UTC) Received: by mail-io1-f67.google.com with SMTP id y197so3755270iof.11 for ; Wed, 22 Sep 2021 08:15:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=SUFlIgkF97LliXUlJb/5UYv8rypWABdjmrEwhMUl3f0=; b=uX2F8zHrzXKQl6pQhFIFZIDJz1njgUJghfXzdm/WO4M+wRGvJEa/6vga8wDPzXm6YM nxFbW6eD9w0uensRtXFDY6a+EMujRuGrs/MIEi1VqQRm+xF7NpkR3wItQ4jn/jTJU+8P 91qT+UkOs83TWgJdnxr12rKFtsQKH1RXeYGdzGjuHI3yelzTEtnAYgf5JuhyR57k7QjH 03RRqXMqVdFYds4wK5ISU8pWziZ4r95//7xHwsrn2ki/0tH9RUeqCvNMYgUpnoU4bkcT 6spoMet5tlJzYAz3rWekUp0Rfo0dNUh8NS8bzjFuxJMLs+6BGyhiofIVlYF0+yHblNk0 GN0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=SUFlIgkF97LliXUlJb/5UYv8rypWABdjmrEwhMUl3f0=; b=gZccP4h+iuLz139Y7M7j7eVx1iu2g9J2qDxyL+j0pBWqBYj20HpDXUak+feBXEFt5h 4jpkT5VzlPWAivgGf+Xdwd/ayf9KcR8Hju8bszUlP6MsV0Hcpg1aPzjhS4niWl/5VXEb M8jehVWSsoi2sK8/BjvB9sbs950YFZyuilrfEWe3MHQWrrt5vAoQfC5r0ufe+Ky/v5XJ ND/Exil/6uRVK5abR2Q3RiZ1prV2PkAHl8+FUyYSxDfQR8cj9LHjFoG0fj24flE9sn2u 9bukKmRavvzwL7khUfnnuSnsu2Ojt/VXbpgt9WRCqmnC/MRWWNOO82XAB+Yx3YhzpkH8 QFMA== X-Gm-Message-State: AOAM533UNS2TGt+KfOMqzRi8KaKEZGqRzs1pOH0xMcciiytDJ+4gD+K+ +fgez7MAx2ij9TYjaizJc3eI/w== X-Google-Smtp-Source: ABdhPJxPX7caP6ZoDNZKXdHXDn97sVpv2Jh7Xuz7w6ET4m37RfPtwclpL1tJnUZj6ns0sm4V3IBCPQ== X-Received: by 2002:a6b:6b08:: with SMTP id g8mr92580ioc.199.1632323747923; Wed, 22 Sep 2021 08:15:47 -0700 (PDT) Received: from [192.168.1.30] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id b12sm1142541ilv.46.2021.09.22.08.15.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Sep 2021 08:15:47 -0700 (PDT) Subject: Re: [syzbot] INFO: rcu detected stall in sys_recvmmsg To: Paolo Abeni , syzbot , 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 References: <0000000000003216d705cc8a62d6@google.com> <89d72aca4e30335a03322612cf164420be11d8eb.camel@redhat.com> From: Jens Axboe Message-ID: <16c414f0-8399-e945-825e-fe8ac1be4e08@kernel.dk> Date: Wed, 22 Sep 2021 09:15:46 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <89d72aca4e30335a03322612cf164420be11d8eb.camel@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 9/22/21 9:13 AM, Paolo Abeni wrote: > 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. This seems to happen quite often, and I'm guessing it's mostly likely due to the test being run not always triggering the issue. Hence you end up with git bisection results that go off into the weeds. -- Jens Axboe