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Sun, 01 Nov 2026 10:25:28 -0800 (PST) Date: Sun, 01 Nov 2026 10:25:28 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ae78418.6552420f.2a0efc.005a.GAE@google.com> Subject: [syzbot] [io-uring?] WARNING in io_sq_thread_stop From: syzbot To: axboe@kernel.dk, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: bd5c762ac051 Merge tag 'scsi-misc' of git://git.kernel.org.. git tree: upstream console+strace: https://syzkaller.appspot.com/x/log.txt?x=176b0981580000 kernel config: https://syzkaller.appspot.com/x/.config?x=27aa0e260943f70b dashboard link: https://syzkaller.appspot.com/bug?extid=675af112519ca34f5502 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1096ccb1580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1496ccb1580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/63d7454ecf30/disk-bd5c762a.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/07607d1cf7ed/vmlinux-bd5c762a.xz kernel image: https://storage.googleapis.com/syzbot-assets/2eb94eb9d0af/bzImage-bd5c762a.xz The issue was bisected to: commit 22d9db9fd64a493525d692b32c556875b7254665 Author: Jens Axboe Date: Fri Oct 30 13:27:28 2026 +0000 io_uring/sqpoll: don't attach to a thread that is canceling bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1024562d580000 final oops: https://syzkaller.appspot.com/x/report.txt?x=1224562d580000 console output: https://syzkaller.appspot.com/x/log.txt?x=1424562d580000 AI-generated root cause summary: When an io_uring SQPOLL thread terminates prematurely (e.g., due to a fatal signal), io_sq_thread() sets the IO_SQ_THREAD_SHOULD_STOP bit in sqd->state before exiting. Later, when the ring is cleaned up during io_ring_exit_work(), io_put_sq_data() calls io_sq_thread_stop(), which checks WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state)) under the assumption that the stop bit is not yet set. This causes a benign WARN_ON_ONCE to trigger; subsequent cleanup proceeds normally without leaking memory or corrupting state. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=675af112519ca34f5502 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+675af112519ca34f5502@syzkaller.appspotmail.com Fixes: 22d9db9fd64a ("io_uring/sqpoll: don't attach to a thread that is canceling") ------------[ cut here ]------------ test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state) WARNING: io_uring/sqpoll.c:88 at io_sq_thread_stop+0x17e/0x1a0 io_uring/sqpoll.c:88, CPU#0: kworker/u8:2/48 Modules linked in: CPU: 0 UID: 0 PID: 48 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026 Workqueue: iou_exit io_ring_exit_work RIP: 0010:io_sq_thread_stop+0x17e/0x1a0 io_uring/sqpoll.c:88 Code: c6 05 cb df e9 0b 01 48 c7 c7 a0 da ea 8b be 26 00 00 00 48 c7 c2 e0 da ea 8b e8 dd 05 ce fc e9 4f ff ff ff e8 e3 d8 f2 fc 90 <0f> 0b 90 e9 e1 fe ff ff e8 d5 d8 f2 fc 90 0f 0b 90 e9 6e ff ff ff RSP: 0018:ffffc90000ba7890 EFLAGS: 00010293 RAX: ffffffff84d5061d RBX: ffff888030ac3400 RCX: ffff888022291f40 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: ffffed10061586ab R12: 0000000000000001 R13: 0000000000000000 R14: ffff888030ac3550 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff888124718000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055556aef1340 CR3: 000000003f44e000 CR4: 00000000003526f0 Call Trace: io_put_sq_data+0x8a/0x150 io_uring/sqpoll.c:105 io_sq_thread_finish+0x1fd/0x240 io_uring/sqpoll.c:130 io_ring_ctx_free+0x2d/0x5e0 io_uring/io_uring.c:2322 io_ring_exit_work+0x5b1/0x640 io_uring/io_uring.c:2658 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 --- 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 If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup