Hello, syzbot found the following issue on: HEAD commit: 3dbdb38e Merge branch 'for-5.14' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=121231c4300000 kernel config: https://syzkaller.appspot.com/x/.config?x=a1fcf15a09815757 dashboard link: https://syzkaller.appspot.com/bug?extid=f61766d5763f9e7a118f Unfortunately, I don't have any reproducer for this issue yet. IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+f61766d5763f9e7a118f@xxxxxxxxxxxxxxxxxxxxxxxxx ====================================================== WARNING: possible circular locking dependency detected 5.13.0-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/28137 is trying to acquire lock: ffff88801fddc138 ((wq_completion)loop7){+.+.}-{0:0}, at: flush_workqueue+0xe1/0x1600 kernel/workqueue.c:2784 but task is already holding lock: ffff88801e95b468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x95/0x1550 drivers/block/loop.c:1286 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&lo->lo_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104 loop_control_ioctl drivers/block/loop.c:2427 [inline] loop_control_ioctl+0x20f/0x480 drivers/block/loop.c:2403 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl fs/ioctl.c:1055 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055 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 -> #5 (loop_ctl_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104 loop_probe+0xc7/0x150 drivers/block/loop.c:2397 blk_request_module+0x111/0x1d0 block/genhd.c:660 blkdev_get_no_open+0x1d5/0x250 fs/block_dev.c:1332 blkdev_get_by_dev.part.0+0x25/0xdd0 fs/block_dev.c:1395 blkdev_get_by_dev+0x6b/0x80 fs/block_dev.c:1448 swsusp_check+0x4d/0x270 kernel/power/swap.c:1525 software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:974 software_resume kernel/power/hibernate.c:84 [inline] resume_store+0x147/0x170 kernel/power/hibernate.c:1176 kobj_attr_store+0x50/0x80 lib/kobject.c:856 sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139 kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296 call_write_iter include/linux/fs.h:2114 [inline] new_sync_write+0x426/0x650 fs/read_write.c:518 vfs_write+0x796/0xa30 fs/read_write.c:605 ksys_write+0x12d/0x250 fs/read_write.c:658 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 -> #4 (major_names_lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104 blkdev_show+0x27/0x160 block/genhd.c:179 devinfo_show+0xc1/0xf0 fs/proc/devices.c:22 seq_read_iter+0xb58/0x11e0 fs/seq_file.c:269 proc_reg_read_iter+0x1fb/0x2d0 fs/proc/inode.c:300 call_read_iter include/linux/fs.h:2108 [inline] new_sync_read+0x41e/0x6e0 fs/read_write.c:415 vfs_read+0x35c/0x570 fs/read_write.c:496 ksys_read+0x12d/0x250 fs/read_write.c:634 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 -> #3 (&p->lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x12a/0x10a0 kernel/locking/mutex.c:1104 seq_read_iter+0xdf/0x11e0 fs/seq_file.c:179 proc_reg_read_iter+0x1fb/0x2d0 fs/proc/inode.c:300 call_read_iter include/linux/fs.h:2108 [inline] generic_file_splice_read+0x450/0x6c0 fs/splice.c:311 do_splice_to+0x1bf/0x250 fs/splice.c:796 splice_direct_to_actor+0x2c2/0x8c0 fs/splice.c:870 do_splice_direct+0x1b3/0x280 fs/splice.c:979 do_sendfile+0x9f0/0x1110 fs/read_write.c:1260 __do_sys_sendfile64 fs/read_write.c:1325 [inline] __se_sys_sendfile64 fs/read_write.c:1311 [inline] __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1311 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 -> #2 (sb_writers#3){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1763 [inline] sb_start_write include/linux/fs.h:1833 [inline] file_start_write include/linux/fs.h:3034 [inline] lo_write_bvec+0x3ed/0x6c0 drivers/block/loop.c:286 lo_write_simple drivers/block/loop.c:309 [inline] do_req_filebacked drivers/block/loop.c:627 [inline] loop_handle_cmd drivers/block/loop.c:2140 [inline] loop_process_work+0xc60/0x24e0 drivers/block/loop.c:2180 process_one_work+0x98d/0x1630 kernel/workqueue.c:2276 worker_thread+0x658/0x11f0 kernel/workqueue.c:2422 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}: process_one_work+0x8fc/0x1630 kernel/workqueue.c:2252 worker_thread+0x658/0x11f0 kernel/workqueue.c:2422 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #0 ((wq_completion)loop7){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3051 [inline] check_prevs_add kernel/locking/lockdep.c:3174 [inline] validate_chain kernel/locking/lockdep.c:3789 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 flush_workqueue+0x110/0x1600 kernel/workqueue.c:2787 drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2952 destroy_workqueue+0x71/0x800 kernel/workqueue.c:4383 __loop_clr_fd+0x1f8/0x1550 drivers/block/loop.c:1304 loop_clr_fd drivers/block/loop.c:1430 [inline] lo_ioctl+0x3c3/0x1600 drivers/block/loop.c:1788 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:585 block_ioctl+0xf9/0x140 fs/block_dev.c:1602 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl fs/ioctl.c:1055 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055 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 other info that might help us debug this: Chain exists of: (wq_completion)loop7 --> loop_ctl_mutex --> &lo->lo_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&lo->lo_mutex); lock(loop_ctl_mutex); lock(&lo->lo_mutex); lock((wq_completion)loop7); *** DEADLOCK *** 1 lock held by syz-executor.4/28137: #0: ffff88801e95b468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0x95/0x1550 drivers/block/loop.c:1286 stack backtrace: CPU: 0 PID: 28137 Comm: syz-executor.4 Not tainted 5.13.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:96 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2131 check_prev_add kernel/locking/lockdep.c:3051 [inline] check_prevs_add kernel/locking/lockdep.c:3174 [inline] validate_chain kernel/locking/lockdep.c:3789 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 flush_workqueue+0x110/0x1600 kernel/workqueue.c:2787 drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2952 destroy_workqueue+0x71/0x800 kernel/workqueue.c:4383 __loop_clr_fd+0x1f8/0x1550 drivers/block/loop.c:1304 loop_clr_fd drivers/block/loop.c:1430 [inline] lo_ioctl+0x3c3/0x1600 drivers/block/loop.c:1788 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:585 block_ioctl+0xf9/0x140 fs/block_dev.c:1602 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl fs/ioctl.c:1055 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:1055 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: 0033:0x4665d9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc7e175f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000056c0f0 RCX: 00000000004665d9 RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000004 RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0f0 R13: 0000000000a9fb1f R14: 00007fc7e175f300 R15: 0000000000022000 --- This report is generated by a bot. 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