====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ udevd/5997 is trying to acquire lock: ffff88802c815a68 (&nsock->tx_lock){+.+.}-{4:4}, at: nbd_handle_cmd drivers/block/nbd.c:1143 [inline] ffff88802c815a68 (&nsock->tx_lock){+.+.}-{4:4}, at: nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207 but task is already holding lock: ffff888027b2e178 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0xa70/0x1910 block/blk-mq.c:2148 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xdcc/0x1600 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386 blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997 __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230 blk_finish_plug block/blk-core.c:1257 [inline] __submit_bio+0x28d/0x580 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753 submit_bh fs/buffer.c:2842 [inline] block_read_full_folio+0x7b7/0x830 fs/buffer.c:2458 filemap_read_folio+0x137/0x3b0 mm/filemap.c:2502 do_read_cache_folio+0x358/0x590 mm/filemap.c:4102 read_mapping_folio include/linux/pagemap.h:1028 [inline] read_part_sector+0xb6/0x2b0 block/partitions/core.c:723 adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360 check_partition block/partitions/core.c:142 [inline] blk_add_partitions block/partitions/core.c:590 [inline] bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694 blkdev_get_whole+0x380/0x510 block/bdev.c:764 bdev_open+0x31e/0xd30 block/bdev.c:973 blkdev_open+0x470/0x610 block/fops.c:697 do_dentry_open+0x785/0x14e0 fs/open.c:949 vfs_open+0x3b/0x340 fs/open.c:1081 do_open fs/namei.c:4693 [inline] path_openat+0x2e08/0x3860 fs/namei.c:4852 do_file_open+0x23e/0x4a0 fs/namei.c:4881 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:199 [inline] __synchronize_srcu+0xca/0x3e0 kernel/rcu/srcutree.c:1505 elevator_switch+0x1e8/0x7a0 block/elevator.c:576 elevator_change+0x2cc/0x450 block/elevator.c:681 elevator_set_default+0x36c/0x430 block/elevator.c:754 blk_register_queue+0x3e9/0x4e0 block/blk-sysfs.c:987 __add_disk+0x677/0xd50 block/genhd.c:528 add_disk_fwnode+0xfb/0x480 block/genhd.c:597 add_disk include/linux/blkdev.h:793 [inline] nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692 do_one_initcall+0x250/0x8d0 init/main.c:1386 do_initcall_level+0x104/0x190 init/main.c:1448 do_initcalls+0x59/0xa0 init/main.c:1464 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1696 kernel_init+0x1d/0x1d0 init/main.c:1586 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #4 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 elevator_change+0x1b3/0x450 block/elevator.c:679 elevator_set_none+0xb5/0x140 block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5131 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5176 [inline] blk_mq_update_nr_hw_queues+0x5e7/0x1a60 block/blk-mq.c:5241 nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1489 nbd_start_device_ioctl drivers/block/nbd.c:1548 [inline] __nbd_ioctl drivers/block/nbd.c:1623 [inline] nbd_ioctl+0x579/0xe40 drivers/block/nbd.c:1663 blkdev_ioctl+0x5e3/0x740 block/ioctl.c:804 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&q->q_usage_counter(io)#49){++++}-{0:0}: blk_alloc_queue+0x546/0x680 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4450 [inline] __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4497 nbd_dev_add+0x499/0xb50 drivers/block/nbd.c:1954 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692 do_one_initcall+0x250/0x8d0 init/main.c:1386 do_initcall_level+0x104/0x190 init/main.c:1448 do_initcalls+0x59/0xa0 init/main.c:1464 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1696 kernel_init+0x1d/0x1d0 init/main.c:1586 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4310 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4324 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4520 [inline] slab_alloc_node mm/slub.c:4875 [inline] kmem_cache_alloc_node_noprof+0x4a/0x690 mm/slub.c:4950 __alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702 alloc_skb_fclone include/linux/skbuff.h:1433 [inline] tcp_stream_alloc_skb+0x3f/0x580 net/ipv4/tcp.c:945 tcp_sendmsg_locked+0x1375/0x5390 net/ipv4/tcp.c:1270 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1465 sock_sendmsg_nosec+0xf9/0x150 net/socket.c:796 __sock_sendmsg net/socket.c:811 [inline] sock_write_iter+0x302/0x410 net/socket.c:1268 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x61d/0xb90 fs/read_write.c:688 ksys_write+0x150/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (sk_lock-AF_INET){+.+.}-{0:0}: lock_sock_nested+0x41/0x100 net/core/sock.c:3780 lock_sock include/net/sock.h:1713 [inline] inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:915 nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318 recv_work+0x1c7f/0x1d90 drivers/block/nbd.c:1021 process_one_work+0x9ab/0x1780 kernel/workqueue.c:3289 process_scheduled_works kernel/workqueue.c:3380 [inline] worker_thread+0xba8/0x11e0 kernel/workqueue.c:3466 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&nsock->tx_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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0xa70/0x1910 block/blk-mq.c:2148 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xdcc/0x1600 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386 blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997 __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230 blk_finish_plug block/blk-core.c:1257 [inline] __submit_bio+0x28d/0x580 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753 submit_bh fs/buffer.c:2842 [inline] block_read_full_folio+0x7b7/0x830 fs/buffer.c:2458 filemap_read_folio+0x137/0x3b0 mm/filemap.c:2502 do_read_cache_folio+0x358/0x590 mm/filemap.c:4102 read_mapping_folio include/linux/pagemap.h:1028 [inline] read_part_sector+0xb6/0x2b0 block/partitions/core.c:723 adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360 check_partition block/partitions/core.c:142 [inline] blk_add_partitions block/partitions/core.c:590 [inline] bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694 blkdev_get_whole+0x380/0x510 block/bdev.c:764 bdev_open+0x31e/0xd30 block/bdev.c:973 blkdev_open+0x470/0x610 block/fops.c:697 do_dentry_open+0x785/0x14e0 fs/open.c:949 vfs_open+0x3b/0x340 fs/open.c:1081 do_open fs/namei.c:4693 [inline] path_openat+0x2e08/0x3860 fs/namei.c:4852 do_file_open+0x23e/0x4a0 fs/namei.c:4881 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &nsock->tx_lock --> set->srcu --> &cmd->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&cmd->lock); lock(set->srcu); lock(&cmd->lock); lock(&nsock->tx_lock); *** DEADLOCK *** 3 locks held by udevd/5997: #0: ffff888027ac2350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30 block/bdev.c:961 #1: ffff888027a17f18 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline] #1: ffff888027a17f18 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline] #1: ffff888027a17f18 (set->srcu){.+.+}-{0:0}, at: blk_mq_run_hw_queue+0x31f/0x4f0 block/blk-mq.c:2386 #2: ffff888027b2e178 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199 stack backtrace: CPU: 0 UID: 0 PID: 5997 Comm: udevd Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:632 [inline] __mutex_lock+0x19e/0x1420 kernel/locking/mutex.c:794 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0xa70/0x1910 block/blk-mq.c:2148 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xdcc/0x1600 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386 blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997 __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230 blk_finish_plug block/blk-core.c:1257 [inline] __submit_bio+0x28d/0x580 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753 submit_bh fs/buffer.c:2842 [inline] block_read_full_folio+0x7b7/0x830 fs/buffer.c:2458 filemap_read_folio+0x137/0x3b0 mm/filemap.c:2502 do_read_cache_folio+0x358/0x590 mm/filemap.c:4102 read_mapping_folio include/linux/pagemap.h:1028 [inline] read_part_sector+0xb6/0x2b0 block/partitions/core.c:723 adfspart_check_ICS+0xa5/0xa40 block/partitions/acorn.c:360 check_partition block/partitions/core.c:142 [inline] blk_add_partitions block/partitions/core.c:590 [inline] bdev_disk_changed+0x7ba/0x1550 block/partitions/core.c:694 blkdev_get_whole+0x380/0x510 block/bdev.c:764 bdev_open+0x31e/0xd30 block/bdev.c:973 blkdev_open+0x470/0x610 block/fops.c:697 do_dentry_open+0x785/0x14e0 fs/open.c:949 vfs_open+0x3b/0x340 fs/open.c:1081 do_open fs/namei.c:4693 [inline] path_openat+0x2e08/0x3860 fs/namei.c:4852 do_file_open+0x23e/0x4a0 fs/namei.c:4881 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f440b4a7407 Code: 48 89 fa 4c 89 df e8 38 aa 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:00007ffc7fd3dd10 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007f440bb44880 RCX: 00007f440b4a7407 RDX: 00000000000a0800 RSI: 000055b77916ea40 RDI: ffffffffffffff9c RBP: 000055b77915b910 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 000055b779185aa0 R13: 000055b779169190 R14: 0000000000000000 R15: 000055b779185aa0 I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read ldm_validate_partition_table(): Disk read failed. I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 1 prio class 2 Buffer I/O error on dev nbd4, logical block 0, async page read Dev nbd4: unable to read RDB block 0 nbd4: unable to read partition table ldm_validate_partition_table(): Disk read failed. Dev nbd4: unable to read RDB block 0 nbd4: unable to read partition table