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AKwUvBzwi3IrkeN7mwWkffwTBWPB4WlQ4BptJAhOj6oFxJrwyMjXwN+EWerB3AlNJcMFj4FSd8v+p3S1QM3ZrUg=@vger.kernel.org X-Gm-Message-State: AFuF++kKgLVoKT1TOV2bbmwQ5XYhlrLkuLOYebXe9ygZYBz+PKBvg4ZY xVj21P3ouF/EyZldOvxD3V/BIrVJIAbwxaO4dgET0/E9Op0S1b9APbTUyXuE1FP8lstmFXxbNZS YXoUozXi2mvjrMDKv1EeiFR5QGRUwasLrTwSLsCd8Fs2N3axfVGgewwBoM4w= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:2013:b0:6c3:3f02:7514 with SMTP id 006d021491bc7-6c53fa6fb02mr4204858eaf.5.1789415915775; Mon, 14 Sep 2026 12:58:35 -0700 (PDT) Date: Mon, 14 Sep 2026 12:58:35 -0700 In-Reply-To: <6a459145.52c20a74.1f8b39.0005.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6aa851eb.4c28b7d0.c1bba.001f.GAE@google.com> Subject: Re: [syzbot] [comedi?] possible deadlock in comedi_do_insn (2) From: syzbot To: abbotti@mev.co.uk, hsweeten@visionengravers.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 704340f1cd0d Merge tag 'x86_urgent_for_7.3-rc4' of git://g.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=165c9901580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8c5c3949d762a91f dashboard link: https://syzkaller.appspot.com/bug?extid=acd959f649966559199c compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12aa2471580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f26601580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-704340f1.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/e02afc1c5927/vmlinux-704340f1.xz kernel image: https://storage.googleapis.com/syzbot-assets/09cb4a8b3309/bzImage-704340f1.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+acd959f649966559199c@syzkaller.appspotmail.com comedi comedi0: comedi_test: 1000000 microvolt, 100000 microsecond waveform attached comedi comedi1: comedi_bond: 0:2 attached, 32 channels from 1 devices ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.0.17/5908 is trying to acquire lock: ffff8880339978f0 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_do_insn+0x2e/0x360 drivers/comedi/kcomedilib/kcomedilib_main.c:183 but task is already holding lock: ffff8880339970f0 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_unlocked_ioctl+0x180/0x3310 drivers/comedi/comedi_fops.c:2290 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&dev->mutex#4); lock(&dev->mutex#4); *** DEADLOCK *** May be due to missing lock nesting notation locks held by syz.0.17/5908: 1, last CPU#1: #0: ffff8880339970f0 (&dev->mutex#4){+.+.}-{4:4}, at: comedi_unlocked_ioctl+0x180/0x3310 drivers/comedi/comedi_fops.c:2290 stack backtrace: CPU: 1 UID: 0 PID: 5908 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_deadlock_bug.cold+0xbd/0xca kernel/locking/lockdep.c:3085 check_deadlock kernel/locking/lockdep.c:3137 [inline] validate_chain kernel/locking/lockdep.c:3939 [inline] __lock_acquire+0x13f4/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 comedi_do_insn+0x2e/0x360 drivers/comedi/kcomedilib/kcomedilib_main.c:183 comedi_dio_bitfield2+0x3c0/0x420 drivers/comedi/kcomedilib/kcomedilib_main.c:314 bonding_dio_insn_bits+0x2b9/0x570 drivers/comedi/drivers/comedi_bond.c:100 parse_insn+0x1326/0x19f0 drivers/comedi/comedi_fops.c:1613 do_insn_ioctl+0x152/0x4e0 drivers/comedi/comedi_fops.c:1790 comedi_unlocked_ioctl+0xf68/0x3310 drivers/comedi/comedi_fops.c:2422 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9368f9e159 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffcaf8c9638 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f9369225fa0 RCX: 00007f9368f9e159 RDX: 0000200000000400 RSI: 000000008028640c RDI: 0000000000000004 RBP: 00007f936903503b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f9369225fac R14: 00007f9369225fa0 R15: 00007f9369225fa0 --- 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.