syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.223/7016 is trying to acquire lock:
ffff888143334a98 (&q->elevator_lock){+.+.}-{4:4}, at: queue_requests_store+0x3a7/0x670 block/blk-sysfs.c:117

but task is already holding lock:
ffff888143334558 (&q->q_usage_counter(io)#61){++++}-{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)#61){++++}-{0:0}:
       blk_alloc_queue+0x619/0x760 block/blk-core.c:461
       blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4399
       __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4446
       nbd_dev_add+0x492/0xbb0 drivers/block/nbd.c:1951
       nbd_init+0x181/0x320 drivers/block/nbd.c:2688
       do_one_initcall+0x120/0x6e0 init/main.c:1283
       do_initcall_level init/main.c:1345 [inline]
       do_initcalls init/main.c:1361 [inline]
       do_basic_setup init/main.c:1380 [inline]
       kernel_init_freeable+0x5c2/0x910 init/main.c:1593
       kernel_init+0x1c/0x2b0 init/main.c:1483
       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:4269 [inline]
       fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4283
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4897 [inline]
       slab_alloc_node mm/slub.c:5221 [inline]
       kmem_cache_alloc_node_noprof+0x5e/0x770 mm/slub.c:5297
       __alloc_skb+0x2b2/0x380 net/core/skbuff.c:660
       alloc_skb_fclone include/linux/skbuff.h:1433 [inline]
       tcp_stream_alloc_skb+0x34/0x560 net/ipv4/tcp.c:912
       tcp_sendmsg_locked+0x12d9/0x42e0 net/ipv4/tcp.c:1218
       tcp_sendmsg+0x2e/0x50 net/ipv4/tcp.c:1413
       inet_sendmsg+0xb9/0x140 net/ipv4/af_inet.c:853
       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+0x7d0/0x11d0 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/0x4b0 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:3720
       lock_sock include/net/sock.h:1679 [inline]
       inet_shutdown+0x67/0x440 net/ipv4/af_inet.c:907
       nbd_mark_nsock_dead+0xae/0x5d0 drivers/block/nbd.c:318
       recv_work+0x671/0xa80 drivers/block/nbd.c:1018
       process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3263
       process_scheduled_works kernel/workqueue.c:3346 [inline]
       worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
       kthread+0x3c5/0x780 kernel/kthread.c:463
       ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #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:2129
       __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:2367
       blk_mq_dispatch_list+0x514/0x1310 block/blk-mq.c:2928
       blk_mq_flush_plug_list block/blk-mq.c:2976 [inline]
       blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2948
       __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+0x545/0x690 block/blk-core.c:651
       __submit_bio_noacct_mq block/blk-core.c:724 [inline]
       submit_bio_noacct_nocheck+0x53d/0xc10 block/blk-core.c:755
       submit_bio_noacct+0xbbb/0x1f60 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:2444
       do_read_cache_folio+0x263/0x5c0 mm/filemap.c:4024
       read_mapping_folio include/linux/pagemap.h:999 [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: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:1097
       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:1437
       do_sys_open fs/open.c:1452 [inline]
       __do_sys_openat fs/open.c:1468 [inline]
       __se_sys_openat fs/open.c:1463 [inline]
       __x64_sys_openat+0x174/0x210 fs/open.c:1463
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4b0 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:2129
       __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:2367
       blk_mq_dispatch_list+0x514/0x1310 block/blk-mq.c:2928
       blk_mq_flush_plug_list block/blk-mq.c:2976 [inline]
       blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2948
       __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+0x545/0x690 block/blk-core.c:651
       __submit_bio_noacct_mq block/blk-core.c:724 [inline]
       submit_bio_noacct_nocheck+0x53d/0xc10 block/blk-core.c:755
       submit_bio_noacct+0xbbb/0x1f60 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:2444
       do_read_cache_folio+0x263/0x5c0 mm/filemap.c:4024
       read_mapping_folio include/linux/pagemap.h:999 [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: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:1097
       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:1437
       do_sys_open fs/open.c:1452 [inline]
       __do_sys_openat fs/open.c:1468 [inline]
       __se_sys_openat fs/open.c:1463 [inline]
       __x64_sys_openat+0x174/0x210 fs/open.c:1463
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4b0 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+0x391/0x5d0 block/elevator.c:691
       elevator_set_default+0x2e9/0x380 block/elevator.c:767
       blk_register_queue+0x384/0x4e0 block/blk-sysfs.c:942
       __add_disk+0x74a/0xf00 block/genhd.c:528
       add_disk_fwnode+0x13f/0x5d0 block/genhd.c:597
       add_disk include/linux/blkdev.h:775 [inline]
       nbd_dev_add+0x783/0xbb0 drivers/block/nbd.c:1981
       nbd_init+0x181/0x320 drivers/block/nbd.c:2688
       do_one_initcall+0x120/0x6e0 init/main.c:1283
       do_initcall_level init/main.c:1345 [inline]
       do_initcalls init/main.c:1361 [inline]
       do_basic_setup init/main.c:1380 [inline]
       kernel_init_freeable+0x5c2/0x910 init/main.c:1593
       kernel_init+0x1c/0x2b0 init/main.c:1483
       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
       queue_requests_store+0x3a7/0x670 block/blk-sysfs.c:117
       queue_attr_store+0x26b/0x310 block/blk-sysfs.c:869
       sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:142
       kernfs_fop_write_iter+0x3ac/0x570 fs/kernfs/file.c:352
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x7d0/0x11d0 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/0x4b0 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)#61

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&q->q_usage_counter(io)#61);
                               lock(fs_reclaim);
                               lock(&q->q_usage_counter(io)#61);
  lock(&q->elevator_lock);

 *** DEADLOCK ***

7 locks held by syz.1.223/7016:
 #0: ffff88802a6e5b38 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1232
 #1: ffff8880241a4420 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738
 #2: ffff88807cfb7088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x570 fs/kernfs/file.c:343
 #3: ffff888026474008 (kn->active#106){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #3: ffff888026474008 (kn->active#106){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ff/0x570 fs/kernfs/file.c:344
 #4: ffff8880264169c8 (&set->update_nr_hwq_lock){++++}-{4:4}, at: queue_requests_store+0x136/0x670 block/blk-sysfs.c:82
 #5: ffff888143334558 (&q->q_usage_counter(io)#61){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205
 #6: ffff888143334590 (&q->q_usage_counter(queue)#45){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205

stack backtrace:
CPU: 0 UID: 0 PID: 7016 Comm: syz.1.223 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 __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
 queue_requests_store+0x3a7/0x670 block/blk-sysfs.c:117
 queue_attr_store+0x26b/0x310 block/blk-sysfs.c:869
 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:142
 kernfs_fop_write_iter+0x3ac/0x570 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7d0/0x11d0 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/0x4b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7d6b38eec9
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:00007f7d6c1b6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f7d6b5e6180 RCX: 00007f7d6b38eec9
RDX: 000000000000fdef RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f7d6b411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7d6b5e6218 R14: 00007f7d6b5e6180 R15: 00007ffea4622f78
 </TASK>