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[82.132.244.154]) by smtp.gmail.com with ESMTPSA id c12-20020a05600c0a4c00b00381141f4967sm21299910wmq.35.2022.04.20.05.38.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Apr 2022 05:38:56 -0700 (PDT) Message-ID: <9ac31ca6-7141-74c0-a22b-4d908839d8e7@gmail.com> Date: Wed, 20 Apr 2022 13:38:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [syzbot] possible deadlock in io_disarm_next Content-Language: en-US To: syzbot , axboe@kernel.dk, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <000000000000626ce805dd13108c@google.com> From: Pavel Begunkov In-Reply-To: <000000000000626ce805dd13108c@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 4/20/22 11:00, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 634de1db0e9b Add linux-next specific files for 20220419 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=10c92db8f00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=bbd6f9b0a89865b0 > dashboard link: https://syzkaller.appspot.com/bug?extid=57e67273f92d7f5f1931 > 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=10a02f68f00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=138e3008f00000 > > The issue was bisected to: > > commit 78bfbdd1a4977df1dded20f9783a6ec174e67ef8 > Author: Pavel Begunkov > Date: Fri Apr 15 21:08:23 2022 +0000 > > io_uring: kill io_put_req_deferred() #syz test: https://github.com/isilence/linux.git syz_timeout_deadlock > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13039c0cf00000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=10839c0cf00000 > console output: https://syzkaller.appspot.com/x/log.txt?x=17039c0cf00000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+57e67273f92d7f5f1931@syzkaller.appspotmail.com > Fixes: 78bfbdd1a497 ("io_uring: kill io_put_req_deferred()") > > ============================================ > WARNING: possible recursive locking detected > 5.18.0-rc3-next-20220419-syzkaller #0 Not tainted > -------------------------------------------- > syz-executor162/3588 is trying to acquire lock: > ffff888011a453d8 (&ctx->timeout_lock){....}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:379 [inline] > ffff888011a453d8 (&ctx->timeout_lock){....}-{2:2}, at: io_disarm_next+0x545/0xaa0 fs/io_uring.c:2452 > > but task is already holding lock: > ffff888011a453d8 (&ctx->timeout_lock){....}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:379 [inline] > ffff888011a453d8 (&ctx->timeout_lock){....}-{2:2}, at: io_kill_timeouts+0x4c/0x227 fs/io_uring.c:10432 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&ctx->timeout_lock); > lock(&ctx->timeout_lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 2 locks held by syz-executor162/3588: > #0: ffff888011a45398 (&ctx->completion_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline] > #0: ffff888011a45398 (&ctx->completion_lock){+.+.}-{2:2}, at: io_kill_timeouts+0x38/0x227 fs/io_uring.c:10431 > #1: ffff888011a453d8 (&ctx->timeout_lock){....}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:379 [inline] > #1: ffff888011a453d8 (&ctx->timeout_lock){....}-{2:2}, at: io_kill_timeouts+0x4c/0x227 fs/io_uring.c:10432 > > stack backtrace: > CPU: 1 PID: 3588 Comm: syz-executor162 Not tainted 5.18.0-rc3-next-20220419-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: > > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > print_deadlock_bug kernel/locking/lockdep.c:2988 [inline] > check_deadlock kernel/locking/lockdep.c:3031 [inline] > validate_chain kernel/locking/lockdep.c:3816 [inline] > __lock_acquire.cold+0x1f5/0x3b4 kernel/locking/lockdep.c:5053 > lock_acquire kernel/locking/lockdep.c:5665 [inline] > lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5630 > __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline] > _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170 > spin_lock_irq include/linux/spinlock.h:379 [inline] > io_disarm_next+0x545/0xaa0 fs/io_uring.c:2452 > __io_req_complete_post+0x794/0xd90 fs/io_uring.c:2200 > io_kill_timeout fs/io_uring.c:1815 [inline] > io_kill_timeout+0x210/0x21d fs/io_uring.c:1803 > io_kill_timeouts+0xe2/0x227 fs/io_uring.c:10435 > io_ring_ctx_wait_and_kill+0x1eb/0x360 fs/io_uring.c:10462 > io_uring_release+0x42/0x46 fs/io_uring.c:10483 > __fput+0x277/0x9d0 fs/file_table.c:317 > task_work_run+0xdd/0x1a0 kernel/task_work.c:164 > exit_task_work include/linux/task_work.h:37 [inline] > do_exit+0xaff/0x2a00 kernel/exit.c:796 > do_group_exit+0xd2/0x2f0 kernel/exit.c:926 > __do_sys_exit_group kernel/exit.c:937 [inline] > __se_sys_exit_group kernel/exit.c:935 [inline] > __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:935 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7f786cb8ccb9 > Code: Unable to access opcode bytes at RIP 0x7f786cb8cc8f. > RSP: 002b:00007ffcf6b5b088 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 > RAX: ffffffffffffffda RBX: 00007f786cc01350 RCX: 00007f786cb8ccb9 > RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000 > RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f786cc01350 > R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001 > > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > syzbot can test patches for this issue, for details see: > https://goo.gl/tpsmEJ#testing-patches -- Pavel Begunkov