====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.335/7296 is trying to acquire lock: ffff8881417b98b0 (&q->elevator_lock){+.+.}-{4:4}, at: elevator_change+0x1ed/0x570 block/elevator.c:682 but task is already holding lock: ffff8881417b9370 (&q->q_usage_counter(io)#66){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:206 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&q->q_usage_counter(io)#66){++++}-{0:0}: blk_alloc_queue+0x610/0x750 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4415 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4462 null_add_dev+0xf2e/0x1eb0 drivers/block/null_blk/main.c:1999 null_create_dev drivers/block/null_blk/main.c:2097 [inline] null_init+0x2c9/0x610 drivers/block/null_blk/main.c:2169 do_one_initcall+0x123/0x680 init/main.c:1378 do_initcall_level init/main.c:1440 [inline] do_initcalls init/main.c:1456 [inline] do_basic_setup init/main.c:1475 [inline] kernel_init_freeable+0x5c8/0x920 init/main.c:1688 kernel_init+0x1c/0x2b0 init/main.c:1578 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #5 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4301 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4315 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4904 [inline] slab_alloc_node mm/slub.c:5239 [inline] kmem_cache_alloc_node_noprof+0x5e/0x800 mm/slub.c:5315 __alloc_skb+0x156/0x410 net/core/skbuff.c:679 alloc_skb_fclone include/linux/skbuff.h:1433 [inline] tcp_stream_alloc_skb+0x34/0x670 net/ipv4/tcp.c:910 tcp_sendmsg_locked+0x12de/0x42a0 net/ipv4/tcp.c:1217 tcp_sendmsg+0x2e/0x50 net/ipv4/tcp.c:1412 inet_sendmsg+0xb9/0x140 net/ipv4/af_inet.c:859 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] sock_write_iter+0x509/0x610 net/socket.c:1195 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x1f8/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (sk_lock-AF_INET){+.+.}-{0:0}: lock_sock_nested+0x41/0xf0 net/core/sock.c:3780 lock_sock include/net/sock.h:1700 [inline] inet_shutdown+0x67/0x440 net/ipv4/af_inet.c:913 nbd_mark_nsock_dead+0xae/0x5d0 drivers/block/nbd.c:318 recv_work+0x66b/0xa70 drivers/block/nbd.c:1021 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257 process_scheduled_works kernel/workqueue.c:3340 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #3 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1aa/0x1ca0 kernel/locking/mutex.c:776 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x423/0x12d0 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x416/0x1e20 block/blk-mq.c:2138 __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+0xcbd/0x15f0 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd8/0x1b0 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x239/0x670 block/blk-mq.c:2376 blk_mq_dispatch_list+0x514/0x1300 block/blk-mq.c:2939 blk_mq_flush_plug_list block/blk-mq.c:2987 [inline] blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2959 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1225 blk_finish_plug block/blk-core.c:1252 [inline] blk_finish_plug block/blk-core.c:1249 [inline] __submit_bio+0x542/0x690 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x53d/0xbe0 block/blk-core.c:755 submit_bio_noacct+0x5bd/0x1f40 block/blk-core.c:879 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x4db/0x850 fs/buffer.c:2461 filemap_read_folio+0xc8/0x2a0 mm/filemap.c:2496 do_read_cache_folio+0x266/0x5c0 mm/filemap.c:4096 read_mapping_folio include/linux/pagemap.h:1017 [inline] read_part_sector+0xd4/0x370 block/partitions/core.c:722 adfspart_check_ICS+0x93/0x940 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+0x723/0x1520 block/partitions/core.c:693 blkdev_get_whole+0x187/0x290 block/bdev.c:765 bdev_open+0x2c7/0xe40 block/bdev.c:974 blkdev_open+0x34e/0x4f0 block/fops.c:698 do_dentry_open+0x748/0x1590 fs/open.c:962 vfs_open+0x82/0x3f0 fs/open.c:1094 do_open fs/namei.c:4628 [inline] path_openat+0x2078/0x3140 fs/namei.c:4787 do_filp_open+0x20b/0x470 fs/namei.c:4814 do_sys_openat2+0x121/0x290 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1aa/0x1ca0 kernel/locking/mutex.c:776 nbd_queue_rq+0xbd/0x12d0 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x416/0x1e20 block/blk-mq.c:2138 __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+0xcbd/0x15f0 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd8/0x1b0 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x239/0x670 block/blk-mq.c:2376 blk_mq_dispatch_list+0x514/0x1300 block/blk-mq.c:2939 blk_mq_flush_plug_list block/blk-mq.c:2987 [inline] blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2959 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1225 blk_finish_plug block/blk-core.c:1252 [inline] blk_finish_plug block/blk-core.c:1249 [inline] __submit_bio+0x542/0x690 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x53d/0xbe0 block/blk-core.c:755 submit_bio_noacct+0x5bd/0x1f40 block/blk-core.c:879 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x4db/0x850 fs/buffer.c:2461 filemap_read_folio+0xc8/0x2a0 mm/filemap.c:2496 do_read_cache_folio+0x266/0x5c0 mm/filemap.c:4096 read_mapping_folio include/linux/pagemap.h:1017 [inline] read_part_sector+0xd4/0x370 block/partitions/core.c:722 adfspart_check_ICS+0x93/0x940 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+0x723/0x1520 block/partitions/core.c:693 blkdev_get_whole+0x187/0x290 block/bdev.c:765 bdev_open+0x2c7/0xe40 block/bdev.c:974 blkdev_open+0x34e/0x4f0 block/fops.c:698 do_dentry_open+0x748/0x1590 fs/open.c:962 vfs_open+0x82/0x3f0 fs/open.c:1094 do_open fs/namei.c:4628 [inline] path_openat+0x2078/0x3140 fs/namei.c:4787 do_filp_open+0x20b/0x470 fs/namei.c:4814 do_sys_openat2+0x121/0x290 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:197 [inline] __synchronize_srcu+0xa2/0x250 kernel/rcu/srcutree.c:1503 blk_mq_wait_quiesce_done block/blk-mq.c:284 [inline] blk_mq_wait_quiesce_done block/blk-mq.c:281 [inline] blk_mq_quiesce_queue block/blk-mq.c:304 [inline] blk_mq_quiesce_queue+0x149/0x1b0 block/blk-mq.c:299 elevator_switch+0x17d/0x7f0 block/elevator.c:576 elevator_change+0x38b/0x570 block/elevator.c:684 elevator_set_default+0x2d2/0x390 block/elevator.c:757 blk_register_queue+0x384/0x4e0 block/blk-sysfs.c:932 __add_disk+0x74a/0xf00 block/genhd.c:528 add_disk_fwnode+0x13f/0x5d0 block/genhd.c:597 add_disk include/linux/blkdev.h:785 [inline] nbd_dev_add+0x783/0xbb0 drivers/block/nbd.c:1984 nbd_init+0x181/0x320 drivers/block/nbd.c:2692 do_one_initcall+0x123/0x680 init/main.c:1378 do_initcall_level init/main.c:1440 [inline] do_initcalls init/main.c:1456 [inline] do_basic_setup init/main.c:1475 [inline] kernel_init_freeable+0x5c8/0x920 init/main.c:1688 kernel_init+0x1c/0x2b0 init/main.c:1578 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #0 (&q->elevator_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+0x1669/0x2890 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1aa/0x1ca0 kernel/locking/mutex.c:776 elevator_change+0x1ed/0x570 block/elevator.c:682 elv_iosched_store+0x3e8/0x4a0 block/elevator.c:815 queue_attr_store+0x26b/0x310 block/blk-sysfs.c:859 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352 iter_file_splice_write+0xa24/0x12b0 fs/splice.c:738 do_splice_from fs/splice.c:938 [inline] direct_splice_actor+0x192/0x6c0 fs/splice.c:1161 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1105 do_splice_direct_actor fs/splice.c:1204 [inline] do_splice_direct+0x174/0x240 fs/splice.c:1230 do_sendfile+0xb06/0xe50 fs/read_write.c:1370 __do_sys_sendfile64 fs/read_write.c:1431 [inline] __se_sys_sendfile64 fs/read_write.c:1417 [inline] __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/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: &q->elevator_lock --> fs_reclaim --> &q->q_usage_counter(io)#66 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#66); lock(fs_reclaim); lock(&q->q_usage_counter(io)#66); lock(&q->elevator_lock); *** DEADLOCK *** 6 locks held by syz.2.335/7296: #0: ffff888035064420 (sb_writers#7){.+.+}-{0:0}, at: splice_direct_to_actor+0x345/0xa30 fs/splice.c:1105 #1: ffff888032086888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x570 fs/kernfs/file.c:343 #2: ffff888141b38008 (kn->active#123){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline] #2: ffff888141b38008 (kn->active#123){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ff/0x570 fs/kernfs/file.c:344 #3: ffff888027289208 (&set->update_nr_hwq_lock){++++}-{4:4}, at: elv_iosched_store+0x3d3/0x4a0 block/elevator.c:813 #4: ffff8881417b9370 (&q->q_usage_counter(io)#66){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:206 #5: ffff8881417b93a8 (&q->q_usage_counter(queue)#49){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:206 stack backtrace: CPU: 1 UID: 0 PID: 7296 Comm: syz.2.335 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x340 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1669/0x2890 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1aa/0x1ca0 kernel/locking/mutex.c:776 elevator_change+0x1ed/0x570 block/elevator.c:682 elv_iosched_store+0x3e8/0x4a0 block/elevator.c:815 queue_attr_store+0x26b/0x310 block/blk-sysfs.c:859 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352 iter_file_splice_write+0xa24/0x12b0 fs/splice.c:738 do_splice_from fs/splice.c:938 [inline] direct_splice_actor+0x192/0x6c0 fs/splice.c:1161 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1105 do_splice_direct_actor fs/splice.c:1204 [inline] do_splice_direct+0x174/0x240 fs/splice.c:1230 do_sendfile+0xb06/0xe50 fs/read_write.c:1370 __do_sys_sendfile64 fs/read_write.c:1431 [inline] __se_sys_sendfile64 fs/read_write.c:1417 [inline] __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff17b18f7c9 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ff1793cd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007ff17b3e6090 RCX: 00007ff17b18f7c9 RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000008 RBP: 00007ff17b213f91 R08: 0000000000000000 R09: 0000000000000000 R10: 000000007ffff000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ff17b3e6128 R14: 00007ff17b3e6090 R15: 00007ffc436a79d8