syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
udevd/5872 is trying to acquire lock:
ffffffff8ea84d40 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8ea84d40 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4521 [inline]
ffffffff8ea84d40 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4876 [inline]
ffffffff8ea84d40 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_node_noprof+0x4a/0x680 mm/slub.c:4951

but task is already holding lock:
ffffffff90162a00 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline]
ffffffff90162a00 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (uevent_sock_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820
       uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline]
       kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410
       kobject_uevent_env+0x566/0x9e0 lib/kobject_uevent.c:611
       device_add+0x544/0xb90 drivers/base/core.c:3672
       device_create_groups_vargs drivers/base/core.c:4388 [inline]
       device_create+0x269/0x300 drivers/base/core.c:4427
       msr_device_create+0x33/0x50 arch/x86/kernel/msr.c:251
       cpuhp_invoke_callback+0x448/0x860 kernel/cpu.c:194
       cpuhp_thread_fun+0x362/0x780 kernel/cpu.c:1109
       smpboot_thread_fn+0x57c/0xa80 kernel/smpboot.c:160
       kthread+0x389/0x470 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

-> #8 (cpuhp_state-up){+.+.}-{0:0}:
       cpuhp_lock_acquire kernel/cpu.c:103 [inline]
       cpuhp_thread_fun+0x127/0x780 kernel/cpu.c:1086
       smpboot_thread_fn+0x57c/0xa80 kernel/smpboot.c:160
       kthread+0x389/0x470 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

-> #7 (cpu_hotplug_lock){++++}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       cpus_read_lock+0x42/0x160 kernel/cpu.c:490
       static_key_disable+0x12/0x20 kernel/jump_label.c:247
       __inet_hash_connect+0x258f/0x25a0 net/ipv4/inet_hashtables.c:1083
       tcp_v4_connect+0xcee/0x1950 net/ipv4/tcp_ipv4.c:306
       __inet_stream_connect+0x258/0xe00 net/ipv4/af_inet.c:684
       inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:755
       __sys_connect_file net/socket.c:2149 [inline]
       __sys_connect+0x323/0x460 net/socket.c:2168
       __do_sys_connect net/socket.c:2174 [inline]
       __se_sys_connect net/socket.c:2171 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2171
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100 net/core/sock.c:3792
       lock_sock include/net/sock.h:1713 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:915
       nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:318
       recv_work+0x1cef/0x1e10 drivers/block/nbd.c:1021
       process_one_work kernel/workqueue.c:3314 [inline]
       process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478
       kthread+0x389/0x470 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

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820
       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:2148
       __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_hw_queue+0x348/0x4f0 block/blk-mq.c:2387
       blk_mq_dispatch_list+0xd11/0xe10 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x45f/0x540 block/blk-mq.c:2997
       __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x465/0x560 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x2f4/0xa40 block/blk-core.c:753
       submit_bh fs/buffer.c:2742 [inline]
       block_read_full_folio+0x7b7/0x830 fs/buffer.c:2358
       filemap_read_folio+0x12c/0x3a0 mm/filemap.c:2502
       do_read_cache_folio+0x354/0x590 mm/filemap.c:4107
       read_mapping_folio include/linux/pagemap.h:1017 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:724
       adfspart_check_ICS+0xb1/0x960 block/partitions/acorn.c:356
       check_partition block/partitions/core.c:143 [inline]
       blk_add_partitions block/partitions/core.c:591 [inline]
       bdev_disk_changed+0x82b/0x1780 block/partitions/core.c:695
       blkdev_get_whole+0x372/0x510 block/bdev.c:756
       bdev_open+0x324/0xd70 block/bdev.c:965
       blkdev_open+0x461/0x600 block/fops.c:697
       do_dentry_open+0x816/0x1380 fs/open.c:947
       vfs_open+0x3b/0x340 fs/open.c:1079
       do_open fs/namei.c:4699 [inline]
       path_openat+0x2e3b/0x3890 fs/namei.c:4858
       do_file_open+0x23e/0x4a0 fs/namei.c:4887
       do_sys_openat2+0x113/0x200 fs/open.c:1364
       do_sys_open fs/open.c:1370 [inline]
       __do_sys_openat fs/open.c:1386 [inline]
       __se_sys_openat fs/open.c:1381 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1381
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820
       nbd_queue_rq+0xc1/0x1150 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2148
       __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_hw_queue+0x348/0x4f0 block/blk-mq.c:2387
       blk_mq_dispatch_list+0xd11/0xe10 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x45f/0x540 block/blk-mq.c:2997
       __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x465/0x560 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x2f4/0xa40 block/blk-core.c:753
       submit_bh fs/buffer.c:2742 [inline]
       block_read_full_folio+0x7b7/0x830 fs/buffer.c:2358
       filemap_read_folio+0x12c/0x3a0 mm/filemap.c:2502
       do_read_cache_folio+0x354/0x590 mm/filemap.c:4107
       read_mapping_folio include/linux/pagemap.h:1017 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:724
       adfspart_check_ICS+0xb1/0x960 block/partitions/acorn.c:356
       check_partition block/partitions/core.c:143 [inline]
       blk_add_partitions block/partitions/core.c:591 [inline]
       bdev_disk_changed+0x82b/0x1780 block/partitions/core.c:695
       blkdev_get_whole+0x372/0x510 block/bdev.c:756
       bdev_open+0x324/0xd70 block/bdev.c:965
       blkdev_open+0x461/0x600 block/fops.c:697
       do_dentry_open+0x816/0x1380 fs/open.c:947
       vfs_open+0x3b/0x340 fs/open.c:1079
       do_open fs/namei.c:4699 [inline]
       path_openat+0x2e3b/0x3890 fs/namei.c:4858
       do_file_open+0x23e/0x4a0 fs/namei.c:4887
       do_sys_openat2+0x113/0x200 fs/open.c:1364
       do_sys_open fs/open.c:1370 [inline]
       __do_sys_openat fs/open.c:1386 [inline]
       __se_sys_openat fs/open.c:1381 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1381
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (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:987
       __add_disk+0x6cb/0xe30 block/genhd.c:528
       add_disk_fwnode+0xfb/0x4b0 block/genhd.c:597
       add_disk include/linux/blkdev.h:794 [inline]
       nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:1984
       nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x870 init/main.c:1392
       do_initcall_level+0x10a/0x1a0 init/main.c:1454
       do_initcalls+0x59/0xa0 init/main.c:1470
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1703
       kernel_init+0x1d/0x1d0 init/main.c:1593
       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 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820
       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:5134 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5179 [inline]
       blk_mq_update_nr_hw_queues+0x5ef/0x19f0 block/blk-mq.c:5244
       nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1489
       nbd_genl_connect+0x1597/0x1c10 drivers/block/nbd.c:2239
       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:2555
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1899
       sock_sendmsg_nosec net/socket.c:787 [inline]
       __sock_sendmsg net/socket.c:802 [inline]
       ____sys_sendmsg+0x9b9/0xa20 net/socket.c:2699
       ___sys_sendmsg+0x2a5/0x360 net/socket.c:2753
       __sys_sendmsg net/socket.c:2785 [inline]
       __do_sys_sendmsg net/socket.c:2790 [inline]
       __se_sys_sendmsg net/socket.c:2788 [inline]
       __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2788
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#50){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690 block/blk-core.c:461
       blk_mq_alloc_queue block/blk-mq.c:4453 [inline]
       __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4500
       nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1954
       nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2692
       do_one_initcall+0x250/0x870 init/main.c:1392
       do_initcall_level+0x10a/0x1a0 init/main.c:1454
       do_initcalls+0x59/0xa0 init/main.c:1470
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1703
       kernel_init+0x1d/0x1d0 init/main.c:1593
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       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 kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cd0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       __fs_reclaim_acquire mm/page_alloc.c:4320 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4334
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4521 [inline]
       slab_alloc_node mm/slub.c:4876 [inline]
       kmem_cache_alloc_node_noprof+0x4a/0x680 mm/slub.c:4951
       __alloc_skb+0x1d7/0x7a0 net/core/skbuff.c:702
       alloc_skb include/linux/skbuff.h:1385 [inline]
       alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:289
       uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
       kobject_uevent_net_broadcast+0x2fa/0x560 lib/kobject_uevent.c:410
       kobject_uevent_env+0x566/0x9e0 lib/kobject_uevent.c:611
       nbd_config_put+0x185/0x660 drivers/block/nbd.c:1440
       nbd_release+0xfe/0x140 drivers/block/nbd.c:1756
       bdev_release+0x571/0x690 block/bdev.c:-1
       blkdev_release+0x15/0x20 block/fops.c:705
       __fput+0x418/0xa50 fs/file_table.c:510
       fput_close_sync+0x11f/0x240 fs/file_table.c:615
       __do_sys_close fs/open.c:1507 [inline]
       __se_sys_close fs/open.c:1492 [inline]
       __x64_sys_close+0x7e/0x110 fs/open.c:1492
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 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:
  fs_reclaim --> cpuhp_state-up --> uevent_sock_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(uevent_sock_mutex);
                               lock(cpuhp_state-up);
                               lock(uevent_sock_mutex);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by udevd/5872:
 #0: ffff888026ff8350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_release+0x1b8/0x690 block/bdev.c:1136
 #1: ffff888026fe4260 (&nbd->config_lock){+.+.}-{4:4}, at: refcount_dec_and_mutex_lock+0x30/0xa0 lib/refcount.c:118
 #2: ffffffff90162a00 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline]
 #2: ffffffff90162a00 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410

stack backtrace:
CPU: 1 UID: 0 PID: 5872 Comm: udevd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 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+0x1520/0x2cd0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __fs_reclaim_acquire mm/page_alloc.c:4320 [inline]
 fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4334
 might_alloc include/linux/sched/mm.h:317 [inline]
 slab_pre_alloc_hook mm/slub.c:4521 [inline]
 slab_alloc_node mm/slub.c:4876 [inline]
 kmem_cache_alloc_node_noprof+0x4a/0x680 mm/slub.c:4951
 __alloc_skb+0x1d7/0x7a0 net/core/skbuff.c:702
 alloc_skb include/linux/skbuff.h:1385 [inline]
 alloc_uevent_skb+0x7d/0x230 lib/kobject_uevent.c:289
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x2fa/0x560 lib/kobject_uevent.c:410
 kobject_uevent_env+0x566/0x9e0 lib/kobject_uevent.c:611
 nbd_config_put+0x185/0x660 drivers/block/nbd.c:1440
 nbd_release+0xfe/0x140 drivers/block/nbd.c:1756
 bdev_release+0x571/0x690 block/bdev.c:-1
 blkdev_release+0x15/0x20 block/fops.c:705
 __fput+0x418/0xa50 fs/file_table.c:510
 fput_close_sync+0x11f/0x240 fs/file_table.c:615
 __do_sys_close fs/open.c:1507 [inline]
 __se_sys_close fs/open.c:1492 [inline]
 __x64_sys_close+0x7e/0x110 fs/open.c:1492
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f015caa7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff6510bde0 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007f015d1c6880 RCX: 00007f015caa7407
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 00007f015d1c66e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002
R13: 0000559014074190 R14: 0000000000000008 R15: 00005590140894d0
 </TASK>