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AHgh+Rr52kIH5d8B8+zy/WbpLIT5szEwU3ASTSKGQXAgPrnSV6swyoE+bIs2TkwTVIUZfSweD0sNXbfSAA7nyww=@vger.kernel.org X-Gm-Message-State: AOJu0YzxRqGISNAA/59Ywe9Iuk/idad/u9Aw69rs6+GkOiT0mTNaTCMv GjPxdxIpr1LBPDc9FcgdcOf84ue8DgVp7C+g09SoGGzTboPuYj4Atnhf5BYHflqjwrXJZXVa2oZ C2OZs0uysu3122XGFKF0ofQ2uj8Td72ZNqlsK5g4fj2CcCmui4bwiwsP+260= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:5086:b0:495:fecb:bf9c with SMTP id 5614622812f47-4b2ef292b14mr4012253b6e.6.1787297437075; Fri, 21 Aug 2026 00:30:37 -0700 (PDT) Date: Fri, 21 Aug 2026 00:30:37 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a87fe9d.ae6ddae5.3da009.0029.GAE@google.com> Subject: [syzbot] [usb?] possible deadlock in mdc800_device_open From: syzbot To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: dcb68831eac7 Merge tag 'block-7.2-20260815' of git://git.k.. git tree: upstream console+strace: https://syzkaller.appspot.com/x/log.txt?x=1667ea25580000 kernel config: https://syzkaller.appspot.com/x/.config?x=2ca5f2f2c4197664 dashboard link: https://syzkaller.appspot.com/bug?extid=023b30ebfe0dc4bcfafe compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15fe2679580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=167fda79580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/2f9d6a54222e/disk-dcb68831.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/0b52c510b447/vmlinux-dcb68831.xz kernel image: https://storage.googleapis.com/syzbot-assets/f8d408f8474e/bzImage-dcb68831.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+023b30ebfe0dc4bcfafe@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor372/5624 is trying to acquire lock: ffff888029dc0218 (&mdc800->io_lock){+.+.}-{4:4}, at: mdc800_device_open+0x2e/0x470 drivers/usb/image/mdc800.c:611 but task is already holding lock: ffffffff8f8e0868 (minor_rwsem#2){++++}-{4:4}, at: usb_open+0x30/0x1e0 drivers/usb/core/file.c:38 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (minor_rwsem#2){++++}-{4:4}: down_write+0x96/0x200 kernel/locking/rwsem.c:1631 usb_register_dev+0x142/0x5e0 drivers/usb/core/file.c:134 mdc800_usb_probe+0xf96/0x18c0 drivers/usb/image/mdc800.c:485 usb_probe_interface+0x653/0xc60 drivers/usb/core/driver.c:396 call_driver_probe drivers/base/dd.c:-1 [inline] really_probe+0x254/0xae0 drivers/base/dd.c:706 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026 bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500 __device_attach+0x2c4/0x450 drivers/base/dd.c:1098 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153 bus_probe_device+0x12a/0x220 drivers/base/bus.c:620 device_add+0x7d7/0xb80 drivers/base/core.c:3772 usb_set_configuration+0x1ad8/0x2180 drivers/usb/core/message.c:2268 usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250 usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:291 call_driver_probe drivers/base/dd.c:-1 [inline] really_probe+0x254/0xae0 drivers/base/dd.c:706 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898 __device_attach_driver+0x270/0x410 drivers/base/dd.c:1026 bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500 __device_attach+0x2c4/0x450 drivers/base/dd.c:1098 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1153 bus_probe_device+0x12a/0x220 drivers/base/bus.c:620 device_add+0x7d7/0xb80 drivers/base/core.c:3772 usb_new_device+0x9aa/0x1690 drivers/usb/core/hub.c:2703 hub_port_connect drivers/usb/core/hub.c:5575 [inline] hub_port_connect_change drivers/usb/core/hub.c:5715 [inline] port_event drivers/usb/core/hub.c:5879 [inline] hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5961 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x388/0x470 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 -> #0 (&mdc800->io_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 mdc800_device_open+0x2e/0x470 drivers/usb/image/mdc800.c:611 usb_open+0x156/0x1e0 drivers/usb/core/file.c:47 chrdev_open+0x4d9/0x600 fs/char_dev.c:411 do_dentry_open+0x816/0x1380 fs/open.c:947 vfs_open+0x3b/0x340 fs/open.c:1052 do_open fs/namei.c:4700 [inline] path_openat+0x2e44/0x3830 fs/namei.c:4863 do_file_open+0x23e/0x4a0 fs/namei.c:4892 do_sys_openat2+0x115/0x200 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline] __do_sys_openat fs/open.c:1390 [inline] __se_sys_openat fs/open.c:1385 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1385 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(minor_rwsem#2); lock(&mdc800->io_lock); lock(minor_rwsem#2); lock(&mdc800->io_lock); *** DEADLOCK *** 1 lock held by syz-executor372/5624: #0: ffffffff8f8e0868 (minor_rwsem#2){++++}-{4:4}, at: usb_open+0x30/0x1e0 drivers/usb/core/file.c:38 stack backtrace: CPU: 0 UID: 0 PID: 5624 Comm: syz-executor372 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 mdc800_device_open+0x2e/0x470 drivers/usb/image/mdc800.c:611 usb_open+0x156/0x1e0 drivers/usb/core/file.c:47 chrdev_open+0x4d9/0x600 fs/char_dev.c:411 do_dentry_open+0x816/0x1380 fs/open.c:947 vfs_open+0x3b/0x340 fs/open.c:1052 do_open fs/namei.c:4700 [inline] path_openat+0x2e44/0x3830 fs/namei.c:4863 do_file_open+0x23e/0x4a0 fs/namei.c:4892 do_sys_openat2+0x115/0x200 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline] __do_sys_openat fs/open.c:1390 [inline] __se_sys_openat fs/open.c:1385 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1385 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f2ac746d097 Code: 48 89 fa 4c 89 df e8 48 1f 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007ffd29cf7470 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 000055557962c400 RCX: 00007f2ac746d097 RDX: 0000000000000002 RSI: 00007ffd29cf7510 RDI: ffffffffffffff9c RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffd29cf7708 R13: 431bde82d7b634db R14: 00007f2ac74eec40 R15: 0000000000000002 --- 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. 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