====================================================== WARNING: possible circular locking dependency detected 4.19.211-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/10554 is trying to acquire lock: 00000000327a67c6 ((wq_completion)"knbd%d-recv"nbd->index){+.+.}, at: flush_workqueue+0xe8/0x13e0 kernel/workqueue.c:2658 but task is already holding lock: 000000006b2f24af (&nbd->config_lock){+.+.}, at: refcount_dec_and_mutex_lock lib/refcount.c:311 [inline] 000000006b2f24af (&nbd->config_lock){+.+.}, at: refcount_dec_and_mutex_lock+0x4a/0x80 lib/refcount.c:306 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #8 (&nbd->config_lock){+.+.}: nbd_open+0x2e2/0x6f0 drivers/block/nbd.c:1428 __blkdev_get+0x372/0x1480 fs/block_dev.c:1494 blkdev_get+0xb0/0x940 fs/block_dev.c:1627 blkdev_open+0x202/0x290 fs/block_dev.c:1788 do_dentry_open+0x4aa/0x1160 fs/open.c:796 do_last fs/namei.c:3421 [inline] path_openat+0x793/0x2df0 fs/namei.c:3537 do_filp_open+0x18c/0x3f0 fs/namei.c:3567 do_sys_open+0x3b3/0x520 fs/open.c:1085 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #7 (nbd_index_mutex){+.+.}: nbd_open+0x73/0x6f0 drivers/block/nbd.c:1415 __blkdev_get+0x372/0x1480 fs/block_dev.c:1494 blkdev_get+0xb0/0x940 fs/block_dev.c:1627 blkdev_open+0x202/0x290 fs/block_dev.c:1788 do_dentry_open+0x4aa/0x1160 fs/open.c:796 do_last fs/namei.c:3421 [inline] path_openat+0x793/0x2df0 fs/namei.c:3537 do_filp_open+0x18c/0x3f0 fs/namei.c:3567 do_sys_open+0x3b3/0x520 fs/open.c:1085 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #6 (&bdev->bd_mutex){+.+.}: blkdev_put+0x30/0x520 fs/block_dev.c:1839 btrfs_close_bdev fs/btrfs/volumes.c:1033 [inline] btrfs_close_one_device fs/btrfs/volumes.c:1057 [inline] close_fs_devices.part.0+0x24d/0x8e0 fs/btrfs/volumes.c:1085 close_fs_devices fs/btrfs/volumes.c:1117 [inline] btrfs_close_devices+0x95/0x1f0 fs/btrfs/volumes.c:1103 close_ctree+0x3c8/0x850 fs/btrfs/disk-io.c:4047 generic_shutdown_super+0x144/0x370 fs/super.c:456 kill_anon_super+0x36/0x60 fs/super.c:1032 btrfs_kill_super+0x49/0x550 fs/btrfs/super.c:2221 deactivate_locked_super+0x94/0x160 fs/super.c:329 deactivate_super+0x174/0x1a0 fs/super.c:360 cleanup_mnt+0x1a8/0x290 fs/namespace.c:1098 task_work_run+0x148/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #5 (&fs_devs->device_list_mutex){+.+.}: btrfs_finish_chunk_alloc+0x27b/0xf90 fs/btrfs/volumes.c:4938 btrfs_create_pending_block_groups+0x242/0x590 fs/btrfs/extent-tree.c:10134 __btrfs_end_transaction+0x21a/0xb00 fs/btrfs/transaction.c:855 flush_space+0xa41/0xee0 fs/btrfs/extent-tree.c:4861 btrfs_async_reclaim_metadata_space+0x466/0x1050 fs/btrfs/extent-tree.c:4977 process_one_work+0x864/0x1570 kernel/workqueue.c:2153 worker_thread+0x64c/0x1130 kernel/workqueue.c:2296 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 -> #4 (sb_internal#2){.+.+}: sb_start_intwrite include/linux/fs.h:1626 [inline] start_transaction+0xa37/0xf90 fs/btrfs/transaction.c:528 btrfs_dirty_inode+0xe3/0x210 fs/btrfs/inode.c:6165 btrfs_update_time+0x33b/0x3d0 fs/btrfs/inode.c:6207 update_time fs/inode.c:1675 [inline] touch_atime+0x23c/0x2a0 fs/inode.c:1746 file_accessed include/linux/fs.h:2123 [inline] btrfs_file_mmap+0x11b/0x160 fs/btrfs/file.c:2274 call_mmap include/linux/fs.h:1826 [inline] mmap_region+0xc94/0x16b0 mm/mmap.c:1757 do_mmap+0x8e8/0x1080 mm/mmap.c:1530 do_mmap_pgoff include/linux/mm.h:2329 [inline] vm_mmap_pgoff+0x197/0x200 mm/util.c:357 ksys_mmap_pgoff+0x298/0x5a0 mm/mmap.c:1580 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #3 (&mm->mmap_sem){++++}: _copy_to_iter+0x3d0/0xea0 lib/iov_iter.c:564 copy_to_iter include/linux/uio.h:106 [inline] skb_copy_datagram_iter+0x469/0x9e0 net/core/datagram.c:431 skb_copy_datagram_msg include/linux/skbuff.h:3347 [inline] unix_stream_read_actor+0x78/0xc0 net/unix/af_unix.c:2489 unix_stream_read_generic+0x8b9/0x1a40 net/unix/af_unix.c:2410 unix_stream_recvmsg+0xb1/0xf0 net/unix/af_unix.c:2505 sock_recvmsg_nosec net/socket.c:859 [inline] sock_recvmsg net/socket.c:866 [inline] sock_recvmsg net/socket.c:862 [inline] sock_read_iter+0x339/0x470 net/socket.c:944 call_read_iter include/linux/fs.h:1815 [inline] new_sync_read fs/read_write.c:406 [inline] __vfs_read+0x518/0x750 fs/read_write.c:418 vfs_read+0x194/0x3c0 fs/read_write.c:452 ksys_read+0x12b/0x2a0 fs/read_write.c:579 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&u->iolock){+.+.}: unix_stream_read_generic+0x2de/0x1a40 net/unix/af_unix.c:2322 unix_stream_recvmsg+0xb1/0xf0 net/unix/af_unix.c:2505 sock_recvmsg_nosec net/socket.c:859 [inline] sock_recvmsg net/socket.c:866 [inline] sock_recvmsg+0xca/0x110 net/socket.c:862 sock_xmit+0x37d/0x5c0 drivers/block/nbd.c:439 nbd_read_stat drivers/block/nbd.c:633 [inline] recv_work+0x1e9/0x1100 drivers/block/nbd.c:732 process_one_work+0x864/0x1570 kernel/workqueue.c:2153 worker_thread+0x64c/0x1130 kernel/workqueue.c:2296 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 -> #1 ((work_completion)(&args->work)){+.+.}: worker_thread+0x64c/0x1130 kernel/workqueue.c:2296 kthread+0x33f/0x460 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 -> #0 ((wq_completion)"knbd%d-recv"nbd->index){+.+.}: flush_workqueue+0x117/0x13e0 kernel/workqueue.c:2661 drain_workqueue+0x1a5/0x460 kernel/workqueue.c:2826 destroy_workqueue+0x75/0x790 kernel/workqueue.c:4183 nbd_config_put+0x3c5/0x870 drivers/block/nbd.c:1175 nbd_release+0xf4/0x170 drivers/block/nbd.c:1461 __blkdev_put+0x636/0x870 fs/block_dev.c:1819 blkdev_close+0x86/0xb0 fs/block_dev.c:1888 __fput+0x2ce/0x890 fs/file_table.c:278 task_work_run+0x148/0x1c0 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0xbf3/0x2be0 kernel/exit.c:870 do_group_exit+0x125/0x310 kernel/exit.c:967 get_signal+0x3f2/0x1f70 kernel/signal.c:2589 do_signal+0x8f/0x1670 arch/x86/kernel/signal.c:799 exit_to_usermode_loop+0x204/0x2a0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x277/0x2d0 arch/x86/entry/common.c:198 retint_user+0x8/0x18 other info that might help us debug this: Chain exists of: (wq_completion)"knbd%d-recv"nbd->index --> nbd_index_mutex --> &nbd->config_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&nbd->config_lock); lock(nbd_index_mutex); lock(&nbd->config_lock); lock((wq_completion)"knbd%d-recv"nbd->index); *** DEADLOCK *** 2 locks held by syz-executor.4/10554: #0: 0000000007ddf754 (&bdev->bd_mutex){+.+.}, at: __blkdev_put+0xfc/0x870 fs/block_dev.c:1806 #1: 000000006b2f24af (&nbd->config_lock){+.+.}, at: refcount_dec_and_mutex_lock lib/refcount.c:311 [inline] #1: 000000006b2f24af (&nbd->config_lock){+.+.}, at: refcount_dec_and_mutex_lock+0x4a/0x80 lib/refcount.c:306 stack backtrace: CPU: 1 PID: 10554 Comm: syz-executor.4 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fc/0x2ef lib/dump_stack.c:118 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222 check_prev_add kernel/locking/lockdep.c:1866 [inline] check_prevs_add kernel/locking/lockdep.c:1979 [inline] validate_chain kernel/locking/lockdep.c:2420 [inline] __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908 flush_workqueue+0x117/0x13e0 kernel/workqueue.c:2661 drain_workqueue+0x1a5/0x460 kernel/workqueue.c:2826 destroy_workqueue+0x75/0x790 kernel/workqueue.c:4183 nbd_config_put+0x3c5/0x870 drivers/block/nbd.c:1175 nbd_release+0xf4/0x170 drivers/block/nbd.c:1461 __blkdev_put+0x636/0x870 fs/block_dev.c:1819 blkdev_close+0x86/0xb0 fs/block_dev.c:1888 __fput+0x2ce/0x890 fs/file_table.c:278 task_work_run+0x148/0x1c0 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0xbf3/0x2be0 kernel/exit.c:870 do_group_exit+0x125/0x310 kernel/exit.c:967 get_signal+0x3f2/0x1f70 kernel/signal.c:2589 do_signal+0x8f/0x1670 arch/x86/kernel/signal.c:799 exit_to_usermode_loop+0x204/0x2a0 arch/x86/entry/common.c:163 prepare_exit_to_usermode+0x277/0x2d0 arch/x86/entry/common.c:198 retint_user+0x8/0x18 RIP: 0033:0x7fb89c7320f9 Code: Bad RIP value. RSP: 002b:00007fb89aca4118 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 00007fb89c851f80 RCX: 00007fb89c7320f9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 00007fb89c78dae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffd78e366af R14: 00007fb89aca4300 R15: 0000000000022000 device vxlan0 entered promiscuous mode EXT4-fs (loop0): encrypted files will use data=ordered instead of data journaling mode BTRFS warning (device ): duplicate device /dev/loop2 devid 1 generation 8 scanned by syz-executor.2 (10535) EXT4-fs (loop0): Unsupported blocksize for fs encryption BTRFS warning (device ): duplicate device /dev/loop2 devid 1 generation 8 scanned by systemd-udevd (10601) EXT4-fs (loop0): encrypted files will use data=ordered instead of data journaling mode EXT4-fs (loop0): Unsupported blocksize for fs encryption device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode device vxlan0 entered promiscuous mode