====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/0:4/5950 is trying to acquire lock: ffffffff8e642920 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:318 [inline] ffffffff8e642920 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4661 [inline] ffffffff8e642920 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4984 [inline] ffffffff8e642920 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_node_noprof+0x48/0x710 mm/slub.c:5060 but task is already holding lock: ffff88805f26b560 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1676 [inline] ffff88805f26b560 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: __mptcp_push_pending+0x312/0x860 net/mptcp/protocol.c:1552 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (k-sk_lock-AF_INET){+.+.}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 lock_sock_nested+0x48/0x100 net/core/sock.c:3716 lock_sock include/net/sock.h:1676 [inline] mptcp_connect+0x4c3/0x830 net/mptcp/protocol.c:3748 __inet_stream_connect+0x2ab/0xe80 net/ipv4/af_inet.c:677 inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:748 __sys_connect_file net/socket.c:2086 [inline] __sys_connect+0x313/0x440 net/socket.c:2105 __do_sys_connect net/socket.c:2111 [inline] __se_sys_connect net/socket.c:2108 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2108 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #6 (sk_lock-AF_INET){+.+.}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 lock_sock_nested+0x48/0x100 net/core/sock.c:3716 lock_sock include/net/sock.h:1676 [inline] tcp_sendmsg+0x21/0x50 net/ipv4/tcp.c:1392 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg+0x19c/0x270 net/socket.c:729 sock_sendmsg+0x158/0x230 net/socket.c:752 __sock_xmit+0x1c1/0x470 drivers/block/nbd.c:574 sock_xmit drivers/block/nbd.c:602 [inline] nbd_send_cmd+0x863/0x1ba0 drivers/block/nbd.c:712 nbd_handle_cmd drivers/block/nbd.c:1174 [inline] nbd_queue_rq+0xcdb/0xf10 drivers/block/nbd.c:1204 blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2120 __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+0xda4/0x1570 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:2358 blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2967 __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220 blk_finish_plug block/blk-core.c:1247 [inline] __submit_bio+0x2d3/0x5a0 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751 submit_bh fs/buffer.c:2829 [inline] __bread_slow fs/buffer.c:1272 [inline] __bread_gfp+0x216/0x3c0 fs/buffer.c:1518 sb_bread include/linux/buffer_head.h:346 [inline] udf_check_vsd fs/udf/super.c:772 [inline] udf_load_vrs+0x365/0xf20 fs/udf/super.c:2015 udf_fill_super+0x5ad/0x17a0 fs/udf/super.c:2201 get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1691 vfs_get_tree+0x8f/0x2b0 fs/super.c:1751 fc_mount fs/namespace.c:1274 [inline] do_new_mount_fc fs/namespace.c:3726 [inline] do_new_mount+0x302/0xa10 fs/namespace.c:3802 do_mount fs/namespace.c:4125 [inline] __do_sys_mount fs/namespace.c:4324 [inline] __se_sys_mount+0x313/0x410 fs/namespace.c:4301 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&nsock->tx_lock){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760 nbd_handle_cmd drivers/block/nbd.c:1140 [inline] nbd_queue_rq+0x257/0xf10 drivers/block/nbd.c:1204 blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2120 __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+0xda4/0x1570 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:2358 blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2967 __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220 blk_finish_plug block/blk-core.c:1247 [inline] __submit_bio+0x2d3/0x5a0 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x599/0x830 fs/buffer.c:2447 filemap_read_folio+0x114/0x380 mm/filemap.c:2426 do_read_cache_folio+0x350/0x590 mm/filemap.c:3983 read_mapping_folio include/linux/pagemap.h:999 [inline] read_part_sector+0xb6/0x2b0 block/partitions/core.c:722 adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360 check_partition block/partitions/core.c:141 [inline] blk_add_partitions block/partitions/core.c:589 [inline] bdev_disk_changed+0x75c/0x14b0 block/partitions/core.c:693 blkdev_get_whole+0x380/0x510 block/bdev.c:748 bdev_open+0x31e/0xd30 block/bdev.c:957 blkdev_open+0x457/0x600 block/fops.c:694 do_dentry_open+0x950/0x13f0 fs/open.c:965 vfs_open+0x3b/0x340 fs/open.c:1095 do_open fs/namei.c:3887 [inline] path_openat+0x2ee5/0x3830 fs/namei.c:4046 do_filp_open+0x1fa/0x410 fs/namei.c:4073 do_sys_openat2+0x121/0x1c0 fs/open.c:1435 do_sys_open fs/open.c:1450 [inline] __do_sys_openat fs/open.c:1466 [inline] __se_sys_openat fs/open.c:1461 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1461 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (&cmd->lock){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760 nbd_queue_rq+0xc8/0xf10 drivers/block/nbd.c:1196 blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2120 __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+0xda4/0x1570 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:2358 blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2967 __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1220 blk_finish_plug block/blk-core.c:1247 [inline] __submit_bio+0x2d3/0x5a0 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x4ab/0xb50 block/blk-core.c:751 submit_bio_wait+0x104/0x200 block/bio.c:1367 bdev_rw_virt+0x331/0x4c0 block/bio.c:1398 gfs2_read_super+0xff/0x980 fs/gfs2/ops_fstype.c:226 init_names fs/gfs2/ops_fstype.c:337 [inline] gfs2_fill_super+0xfe0/0x20d0 fs/gfs2/ops_fstype.c:1188 get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1691 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1335 vfs_get_tree+0x8f/0x2b0 fs/super.c:1751 fc_mount fs/namespace.c:1274 [inline] do_new_mount_fc fs/namespace.c:3726 [inline] do_new_mount+0x302/0xa10 fs/namespace.c:3802 do_mount fs/namespace.c:4125 [inline] __do_sys_mount fs/namespace.c:4324 [inline] __se_sys_mount+0x313/0x410 fs/namespace.c:4301 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (set->srcu){.+.+}-{0:0}: lock_sync+0xba/0x160 kernel/locking/lockdep.c:5916 srcu_lock_sync include/linux/srcu.h:173 [inline] __synchronize_srcu+0x96/0x3a0 kernel/rcu/srcutree.c:1429 elevator_switch+0x12b/0x640 block/elevator.c:588 elevator_change+0x2d4/0x450 block/elevator.c:690 elevator_set_default+0x186/0x260 block/elevator.c:766 blk_register_queue+0x34e/0x3f0 block/blk-sysfs.c:904 __add_disk+0x677/0xd50 block/genhd.c:528 add_disk_fwnode+0xfc/0x480 block/genhd.c:597 add_disk include/linux/blkdev.h:774 [inline] nbd_dev_add+0x717/0xae0 drivers/block/nbd.c:1973 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2680 do_one_initcall+0x233/0x820 init/main.c:1281 do_initcall_level+0x104/0x190 init/main.c:1343 do_initcalls+0x59/0xa0 init/main.c:1359 kernel_init_freeable+0x334/0x4b0 init/main.c:1591 kernel_init+0x1d/0x1d0 init/main.c:1481 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (&q->elevator_lock){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760 elevator_change+0x19b/0x450 block/elevator.c:688 elevator_set_none+0x42/0xb0 block/elevator.c:781 blk_mq_elv_switch_none block/blk-mq.c:5023 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5066 [inline] blk_mq_update_nr_hw_queues+0x598/0x1aa0 block/blk-mq.c:5124 nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1478 nbd_genl_connect+0x135b/0x18f0 drivers/block/nbd.c:2228 genl_family_rcv_msg_doit+0x212/0x300 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x82c/0x9e0 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg+0x219/0x270 net/socket.c:729 ____sys_sendmsg+0x505/0x830 net/socket.c:2614 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2668 __sys_sendmsg net/socket.c:2700 [inline] __do_sys_sendmsg net/socket.c:2705 [inline] __se_sys_sendmsg net/socket.c:2703 [inline] __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2703 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4400 [inline] __blk_mq_alloc_disk+0x15c/0x340 block/blk-mq.c:4447 nbd_dev_add+0x46c/0xae0 drivers/block/nbd.c:1943 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2680 do_one_initcall+0x233/0x820 init/main.c:1281 do_initcall_level+0x104/0x190 init/main.c:1343 do_initcalls+0x59/0xa0 init/main.c:1359 kernel_init_freeable+0x334/0x4b0 init/main.c:1591 kernel_init+0x1d/0x1d0 init/main.c:1481 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (fs_reclaim){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __fs_reclaim_acquire mm/page_alloc.c:4239 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4253 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4661 [inline] slab_alloc_node mm/slub.c:4984 [inline] kmem_cache_alloc_node_noprof+0x48/0x710 mm/slub.c:5060 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:659 alloc_skb_fclone include/linux/skbuff.h:1427 [inline] __mptcp_do_alloc_tx_skb net/mptcp/protocol.c:1103 [inline] __mptcp_alloc_tx_skb net/mptcp/protocol.c:1122 [inline] mptcp_alloc_tx_skb net/mptcp/protocol.c:1139 [inline] mptcp_sendmsg_frag+0x6a2/0x2d80 net/mptcp/protocol.c:1231 __subflow_push_pending+0x283/0xb40 net/mptcp/protocol.c:1486 __mptcp_push_pending+0x330/0x860 net/mptcp/protocol.c:1557 mptcp_release_cb+0x610/0x960 net/mptcp/protocol.c:3444 release_sock+0x1a0/0x1f0 net/core/sock.c:3734 mptcp_worker+0xa58/0x1160 net/mptcp/protocol.c:2773 process_one_work kernel/workqueue.c:3263 [inline] process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Chain exists of: fs_reclaim --> sk_lock-AF_INET --> k-sk_lock-AF_INET Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(k-sk_lock-AF_INET); lock(sk_lock-AF_INET); lock(k-sk_lock-AF_INET); lock(fs_reclaim); *** DEADLOCK *** 4 locks held by kworker/0:4/5950: #0: ffff88801a871548 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline] #0: ffff88801a871548 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346 #1: ffffc90004777ba0 ((work_completion)(&msk->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline] #1: ffffc90004777ba0 ((work_completion)(&msk->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346 #2: ffff888055863260 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1676 [inline] #2: ffff888055863260 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_worker+0x36/0x1160 net/mptcp/protocol.c:2739 #3: ffff88805f26b560 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1676 [inline] #3: ffff88805f26b560 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: __mptcp_push_pending+0x312/0x860 net/mptcp/protocol.c:1552 stack backtrace: CPU: 0 UID: 0 PID: 5950 Comm: kworker/0:4 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Workqueue: events mptcp_worker Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __fs_reclaim_acquire mm/page_alloc.c:4239 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4253 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4661 [inline] slab_alloc_node mm/slub.c:4984 [inline] kmem_cache_alloc_node_noprof+0x48/0x710 mm/slub.c:5060 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:659 alloc_skb_fclone include/linux/skbuff.h:1427 [inline] __mptcp_do_alloc_tx_skb net/mptcp/protocol.c:1103 [inline] __mptcp_alloc_tx_skb net/mptcp/protocol.c:1122 [inline] mptcp_alloc_tx_skb net/mptcp/protocol.c:1139 [inline] mptcp_sendmsg_frag+0x6a2/0x2d80 net/mptcp/protocol.c:1231 __subflow_push_pending+0x283/0xb40 net/mptcp/protocol.c:1486 __mptcp_push_pending+0x330/0x860 net/mptcp/protocol.c:1557 mptcp_release_cb+0x610/0x960 net/mptcp/protocol.c:3444 release_sock+0x1a0/0x1f0 net/core/sock.c:3734 mptcp_worker+0xa58/0x1160 net/mptcp/protocol.c:2773 process_one_work kernel/workqueue.c:3263 [inline] process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245