====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.6.2206/16245 is trying to acquire lock: ffff888025d7b6f8 (&q->elevator_lock){+.+.}-{4:4}, at: elevator_change+0x17d/0x580 block/elevator.c:688 but task is already holding lock: ffff888025d7b1b8 (&q->q_usage_counter(io)#62){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&q->q_usage_counter(io)#62){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4400 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4447 nbd_dev_add+0x492/0xbb0 drivers/block/nbd.c:1943 nbd_init+0x181/0x320 drivers/block/nbd.c:2680 do_one_initcall+0x120/0x6e0 init/main.c:1271 do_initcall_level init/main.c:1333 [inline] do_initcalls init/main.c:1349 [inline] do_basic_setup init/main.c:1368 [inline] kernel_init_freeable+0x5c2/0x910 init/main.c:1581 kernel_init+0x1c/0x2b0 init/main.c:1471 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #5 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4234 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4248 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4142 [inline] slab_alloc_node mm/slub.c:4220 [inline] kmem_cache_alloc_node_noprof+0x57/0x3b0 mm/slub.c:4292 __alloc_skb+0x2b2/0x380 net/core/skbuff.c:659 alloc_skb include/linux/skbuff.h:1336 [inline] __ip6_append_data+0x2b74/0x4750 net/ipv6/ip6_output.c:1671 ip6_append_data+0x1bd/0x4c0 net/ipv6/ip6_output.c:1860 rawv6_sendmsg+0x163d/0x4820 net/ipv6/raw.c:911 inet_sendmsg+0x11c/0x140 net/ipv4/af_inet.c:851 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg net/socket.c:729 [inline] ____sys_sendmsg+0x973/0xc70 net/socket.c:2617 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2671 __sys_sendmsg+0x16d/0x220 net/socket.c:2703 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (sk_lock-AF_INET6){+.+.}-{0:0}: lock_sock_nested+0x41/0xf0 net/core/sock.c:3711 lock_sock include/net/sock.h:1669 [inline] inet_autobind+0x1a/0x1a0 net/ipv4/af_inet.c:178 inet_send_prepare+0x31b/0x530 net/ipv4/af_inet.c:837 inet_sendmsg+0x43/0x140 net/ipv4/af_inet.c:848 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg net/socket.c:729 [inline] sock_sendmsg+0x37f/0x470 net/socket.c:752 __sock_xmit+0x1e7/0x4f0 drivers/block/nbd.c:574 sock_xmit drivers/block/nbd.c:602 [inline] nbd_send_cmd+0x8e4/0x1c90 drivers/block/nbd.c:712 nbd_handle_cmd drivers/block/nbd.c:1174 [inline] nbd_queue_rq+0x940/0x12d0 drivers/block/nbd.c:1204 blk_mq_dispatch_rq_list+0x416/0x1e20 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+0xcb7/0x15f0 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:2358 blk_mq_dispatch_list+0x514/0x1310 block/blk-mq.c:2919 blk_mq_flush_plug_list block/blk-mq.c:2967 [inline] blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2939 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1222 blk_finish_plug block/blk-core.c:1249 [inline] blk_finish_plug block/blk-core.c:1246 [inline] __submit_bio+0x545/0x690 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x660/0xd30 block/blk-core.c:753 submit_bio_noacct+0xb49/0x1ed0 block/blk-core.c:876 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x4db/0x850 fs/buffer.c:2461 filemap_read_folio+0xc5/0x2a0 mm/filemap.c:2413 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3957 read_mapping_folio include/linux/pagemap.h:991 [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+0x720/0x1520 block/partitions/core.c:693 blkdev_get_whole+0x187/0x290 block/bdev.c:748 bdev_open+0x2c7/0xe40 block/bdev.c:957 blkdev_open+0x34e/0x4f0 block/fops.c:694 do_dentry_open+0x97f/0x1530 fs/open.c:965 vfs_open+0x82/0x3f0 fs/open.c:1095 do_open fs/namei.c:3975 [inline] path_openat+0x1de4/0x2cb0 fs/namei.c:4134 do_filp_open+0x20b/0x470 fs/namei.c:4161 do_sys_openat2+0x11b/0x1d0 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+0x174/0x210 fs/open.c:1461 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 nbd_handle_cmd drivers/block/nbd.c:1140 [inline] nbd_queue_rq+0x423/0x12d0 drivers/block/nbd.c:1204 blk_mq_dispatch_rq_list+0x416/0x1e20 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+0xcb7/0x15f0 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:2358 blk_mq_dispatch_list+0x514/0x1310 block/blk-mq.c:2919 blk_mq_flush_plug_list block/blk-mq.c:2967 [inline] blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2939 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1222 blk_finish_plug block/blk-core.c:1249 [inline] blk_finish_plug block/blk-core.c:1246 [inline] __submit_bio+0x545/0x690 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x660/0xd30 block/blk-core.c:753 submit_bio_noacct+0xb49/0x1ed0 block/blk-core.c:876 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x4db/0x850 fs/buffer.c:2461 filemap_read_folio+0xc5/0x2a0 mm/filemap.c:2413 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3957 read_mapping_folio include/linux/pagemap.h:991 [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+0x720/0x1520 block/partitions/core.c:693 blkdev_get_whole+0x187/0x290 block/bdev.c:748 bdev_open+0x2c7/0xe40 block/bdev.c:957 blkdev_open+0x34e/0x4f0 block/fops.c:694 do_dentry_open+0x97f/0x1530 fs/open.c:965 vfs_open+0x82/0x3f0 fs/open.c:1095 do_open fs/namei.c:3975 [inline] path_openat+0x1de4/0x2cb0 fs/namei.c:4134 do_filp_open+0x20b/0x470 fs/namei.c:4161 do_sys_openat2+0x11b/0x1d0 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+0x174/0x210 fs/open.c:1461 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 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:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 nbd_queue_rq+0xbd/0x12d0 drivers/block/nbd.c:1196 blk_mq_dispatch_rq_list+0x416/0x1e20 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+0xcb7/0x15f0 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:2358 blk_mq_dispatch_list+0x514/0x1310 block/blk-mq.c:2919 blk_mq_flush_plug_list block/blk-mq.c:2967 [inline] blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2939 __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1222 blk_finish_plug block/blk-core.c:1249 [inline] blk_finish_plug block/blk-core.c:1246 [inline] __submit_bio+0x545/0x690 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x660/0xd30 block/blk-core.c:753 submit_bio_noacct+0xb49/0x1ed0 block/blk-core.c:876 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x4db/0x850 fs/buffer.c:2461 filemap_read_folio+0xc5/0x2a0 mm/filemap.c:2413 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3957 read_mapping_folio include/linux/pagemap.h:991 [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+0x720/0x1520 block/partitions/core.c:693 blkdev_get_whole+0x187/0x290 block/bdev.c:748 bdev_open+0x2c7/0xe40 block/bdev.c:957 blkdev_open+0x34e/0x4f0 block/fops.c:694 do_dentry_open+0x97f/0x1530 fs/open.c:965 vfs_open+0x82/0x3f0 fs/open.c:1095 do_open fs/namei.c:3975 [inline] path_openat+0x1de4/0x2cb0 fs/namei.c:4134 do_filp_open+0x20b/0x470 fs/namei.c:4161 do_sys_openat2+0x11b/0x1d0 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+0x174/0x210 fs/open.c:1461 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 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:173 [inline] __synchronize_srcu+0xa1/0x290 kernel/rcu/srcutree.c:1429 blk_mq_wait_quiesce_done block/blk-mq.c:283 [inline] blk_mq_wait_quiesce_done block/blk-mq.c:280 [inline] blk_mq_quiesce_queue block/blk-mq.c:303 [inline] blk_mq_quiesce_queue+0x149/0x1b0 block/blk-mq.c:298 elevator_switch+0x17d/0x810 block/elevator.c:588 elevator_change+0x391/0x580 block/elevator.c:690 elevator_set_default+0x2e9/0x380 block/elevator.c:766 blk_register_queue+0x384/0x4e0 block/blk-sysfs.c:904 __add_disk+0x74a/0xf00 block/genhd.c:528 add_disk_fwnode+0x13f/0x5d0 block/genhd.c:597 add_disk include/linux/blkdev.h:774 [inline] nbd_dev_add+0x783/0xbb0 drivers/block/nbd.c:1973 nbd_init+0x181/0x320 drivers/block/nbd.c:2680 do_one_initcall+0x120/0x6e0 init/main.c:1271 do_initcall_level init/main.c:1333 [inline] do_initcalls init/main.c:1349 [inline] do_basic_setup init/main.c:1368 [inline] kernel_init_freeable+0x5c2/0x910 init/main.c:1581 kernel_init+0x1c/0x2b0 init/main.c:1471 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #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+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 elevator_change+0x17d/0x580 block/elevator.c:688 elv_iosched_store+0x315/0x3c0 block/elevator.c:823 queue_attr_store+0x26b/0x310 block/blk-sysfs.c:831 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x3ac/0x570 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 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)#62 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#62); lock(fs_reclaim); lock(&q->q_usage_counter(io)#62); lock(&q->elevator_lock); *** DEADLOCK *** 7 locks held by syz.6.2206/16245: #0: ffff8880787de478 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1232 #1: ffff88802418a428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738 #2: ffff8880844f4488 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x570 fs/kernfs/file.c:343 #3: ffff888026478f08 (kn->active#251){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline] #3: ffff888026478f08 (kn->active#251){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ff/0x570 fs/kernfs/file.c:344 #4: ffff8880264d0188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: elv_iosched_store+0x35f/0x3c0 block/elevator.c:821 #5: ffff888025d7b1b8 (&q->q_usage_counter(io)#62){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #6: ffff888025d7b1f0 (&q->q_usage_counter(queue)#46){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 stack backtrace: CPU: 0 UID: 0 PID: 16245 Comm: syz.6.2206 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043 check_noncircular+0x14c/0x170 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+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 elevator_change+0x17d/0x580 block/elevator.c:688 elv_iosched_store+0x315/0x3c0 block/elevator.c:823 queue_attr_store+0x26b/0x310 block/blk-sysfs.c:831 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x3ac/0x570 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fdd5e98eec9 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:00007fdd5f76a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fdd5ebe5fa0 RCX: 00007fdd5e98eec9 RDX: 00000000000098c7 RSI: 0000200000000440 RDI: 0000000000000003 RBP: 00007fdd5ea11f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fdd5ebe6038 R14: 00007fdd5ebe5fa0 R15: 00007fff61330288