====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/0:0H/11 is trying to acquire lock: ffff88807db41668 (&nsock->tx_lock){+.+.}-{4:4}, at: nbd_handle_cmd drivers/block/nbd.c:1143 [inline] ffff88807db41668 (&nsock->tx_lock){+.+.}-{4:4}, at: nbd_queue_rq+0x373/0x1150 drivers/block/nbd.c:1207 but task is already holding lock: ffff8880270a0178 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc1/0x1150 drivers/block/nbd.c:1199 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_queue_rq+0xc1/0x1150 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa88/0x14c0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x38b/0x480 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 -> #6 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:199 [inline] __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1481 elevator_switch+0x1e8/0x7b0 block/elevator.c:576 elevator_change+0x2fa/0x480 block/elevator.c:681 elevator_set_default+0x375/0x440 block/elevator.c:754 blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:992 __add_disk+0x6cb/0xe30 block/genhd.c:524 add_disk_fwnode+0x100/0x3a0 block/genhd.c:593 add_disk include/linux/blkdev.h:798 [inline] nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2021 nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2729 do_one_initcall+0x250/0x870 init/main.c:1353 do_initcall_level+0x10a/0x1a0 init/main.c:1415 do_initcalls+0x59/0xa0 init/main.c:1431 kernel_init_freeable+0x29d/0x3e0 init/main.c:1666 kernel_init+0x22/0x1d0 init/main.c:1556 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #5 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 elevator_change+0x1af/0x480 block/elevator.c:679 elevator_set_none+0xb5/0x140 block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5101 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5146 [inline] blk_mq_update_nr_hw_queues+0x5ef/0x19f0 block/blk-mq.c:5211 nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1526 nbd_genl_connect+0x1597/0x1c10 drivers/block/nbd.c:2276 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (&q->q_usage_counter(io)#52){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:504 blk_mq_alloc_queue block/blk-mq.c:4420 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467 nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1991 nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2729 do_one_initcall+0x250/0x870 init/main.c:1353 do_initcall_level+0x10a/0x1a0 init/main.c:1415 do_initcalls+0x59/0xa0 init/main.c:1431 kernel_init_freeable+0x29d/0x3e0 init/main.c:1666 kernel_init+0x22/0x1d0 init/main.c:1556 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4329 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4343 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4537 [inline] slab_alloc_node mm/slub.c:4897 [inline] kmem_cache_alloc_noprof+0x64/0x5f0 mm/slub.c:4931 mt_alloc_one lib/maple_tree.c:139 [inline] mas_alloc_nodes+0x291/0x350 lib/maple_tree.c:1089 mas_preallocate+0x2cf/0x630 lib/maple_tree.c:4961 vma_iter_prealloc mm/vma.h:577 [inline] vma_link+0x123/0x470 mm/vma.c:1849 insert_vm_struct+0x1bf/0x290 mm/vma.c:3328 create_init_stack_vma+0x5c1/0x9b0 mm/vma_exec.c:147 bprm_mm_init fs/exec.c:278 [inline] alloc_bprm+0x50c/0x640 fs/exec.c:1549 class_bprm_constructor fs/exec.c:1559 [inline] kernel_execve+0x85/0x9c0 fs/exec.c:1955 try_to_run_init_process+0x13/0x60 init/main.c:1482 kernel_init+0xb2/0x1d0 init/main.c:1612 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (&mm->mmap_lock){++++}-{4:4}: __might_fault+0xcb/0x130 mm/memory.c:7292 _inline_copy_from_user include/linux/uaccess.h:169 [inline] _copy_from_user+0x28/0xb0 lib/usercopy.c:18 copy_from_user include/linux/uaccess.h:222 [inline] copy_from_sockptr_offset include/linux/sockptr.h:48 [inline] copy_from_sockptr+0x5e/0x90 include/linux/sockptr.h:61 do_ip_setsockopt+0x1ac8/0x2e30 net/ipv4/ip_sockglue.c:1294 ip_setsockopt+0x66/0x110 net/ipv4/ip_sockglue.c:1417 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2397 __sys_setsockopt net/socket.c:2422 [inline] __do_sys_setsockopt net/socket.c:2428 [inline] __se_sys_setsockopt net/socket.c:2425 [inline] __x64_sys_setsockopt+0x13d/0x1b0 net/socket.c:2425 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (sk_lock-AF_INET6-NBD){+.+.}-{0:0}: lock_sock_nested+0x41/0x100 net/core/sock.c:3827 lock_sock include/net/sock.h:1713 [inline] inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:913 nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:318 sock_shutdown+0x15e/0x260 drivers/block/nbd.c:411 nbd_clear_sock+0x24/0x170 drivers/block/nbd.c:1464 nbd_config_put+0x35b/0x660 drivers/block/nbd.c:1488 nbd_genl_connect+0x18f7/0x1c10 drivers/block/nbd.c:2285 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&nsock->tx_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5253 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0x1150 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa88/0x14c0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x38b/0x480 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 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 *** locks held by kworker/0:0H/11: 4, last CPU#0: #0: ffff88801eab2d40 ((wq_completion)kblockd){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline] #0: ffff88801eab2d40 ((wq_completion)kblockd){+.+.}-{0:0}, at: process_scheduled_works+0xa1a/0x14c0 kernel/workqueue.c:3405 #1: ffffc90000107c40 ((work_completion)(&(&hctx->run_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3297 [inline] #1: ffffc90000107c40 ((work_completion)(&(&hctx->run_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa1a/0x14c0 kernel/workqueue.c:3405 #2: ffff8880264a3218 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline] #2: ffff8880264a3218 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline] #2: ffff8880264a3218 (set->srcu){.+.+}-{0:0}, at: blk_mq_run_work_fn+0x144/0x300 block/blk-mq.c:2531 #3: ffff8880270a0178 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc1/0x1150 drivers/block/nbd.c:1199 stack backtrace: CPU: 0 UID: 0 PID: 11 Comm: kworker/0:0H Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: kblockd blk_mq_run_work_fn Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2059 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2191 check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5253 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0x1150 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa88/0x14c0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x38b/0x480 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 block nbd4: Send control failed (result -32) block nbd4: Request send failed, requeueing block nbd4: Dead connection, failed to find a fallback block nbd4: shutting down sockets 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 2 op 0x0:(READ) flags 0x800000 phys_seg 3 prio class 2 Buffer I/O error on dev nbd4, logical block 1, async page read Buffer I/O error on dev nbd4, logical block 2, async page read Buffer I/O error on dev nbd4, logical block 3, async page read I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 4 prio class 2 I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 4 prio class 2 I/O error, dev nbd4, sector 0 op 0x0:(READ) flags 0x800000 phys_seg 4 prio class 2