====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc1-syzkaller-00157-g02adc1490e6d #0 Not tainted ------------------------------------------------------ syz.0.932/8094 is trying to acquire lock: ffffffff908b35a8 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffffffff908b35a8 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline] ffffffff908b35a8 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_env+0xb36/0x1870 lib/kobject_uevent.c:608 but task is already holding lock: ffff8881423acee8 (&q->q_usage_counter(io)#25){++++}-{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: -> #2 (&q->q_usage_counter(io)#25){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x175/0x290 block/blk-mq.c:4396 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4443 loop_add+0x49e/0xb70 drivers/block/loop.c:2014 loop_init+0x164/0x270 drivers/block/loop.c:2249 do_one_initcall+0x120/0x6e0 init/main.c:1273 do_initcall_level init/main.c:1335 [inline] do_initcalls init/main.c:1351 [inline] do_basic_setup init/main.c:1370 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1583 kernel_init+0x1c/0x2b0 init/main.c:1473 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4045 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4059 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4099 [inline] slab_alloc_node mm/slub.c:4177 [inline] kmem_cache_alloc_node_noprof+0x57/0x3b0 mm/slub.c:4249 __alloc_skb+0x2b2/0x380 net/core/skbuff.c:660 alloc_skb include/linux/skbuff.h:1336 [inline] alloc_uevent_skb+0x7d/0x210 lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline] kobject_uevent_env+0xca4/0x1870 lib/kobject_uevent.c:608 kobject_synth_uevent+0x7d4/0x8a0 lib/kobject_uevent.c:207 bus_uevent_store+0x3d/0x90 drivers/base/bus.c:832 bus_attr_store+0x71/0xb0 drivers/base/bus.c:172 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c7/0x1150 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 -> #0 (uevent_sock_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline] kobject_uevent_env+0xb36/0x1870 lib/kobject_uevent.c:608 loop_set_size drivers/block/loop.c:211 [inline] loop_set_size drivers/block/loop.c:208 [inline] loop_set_status+0x9c9/0xb90 drivers/block/loop.c:1254 loop_set_status_old+0x162/0x1d0 drivers/block/loop.c:1353 lo_ioctl+0xb3f/0x2760 drivers/block/loop.c:1523 blkdev_ioctl+0x277/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893 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: uevent_sock_mutex --> fs_reclaim --> &q->q_usage_counter(io)#25 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#25); lock(fs_reclaim); lock(&q->q_usage_counter(io)#25); lock(uevent_sock_mutex); *** DEADLOCK *** 3 locks held by syz.0.932/8094: #0: ffff888142bc5400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2c/0xb90 drivers/block/loop.c:1223 #1: ffff8881423acee8 (&q->q_usage_counter(io)#25){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #2: ffff8881423acf20 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 stack backtrace: CPU: 0 UID: 0 PID: 8094 Comm: syz.0.932 Not tainted 6.16.0-rc1-syzkaller-00157-g02adc1490e6d #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 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:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast lib/kobject_uevent.c:410 [inline] kobject_uevent_env+0xb36/0x1870 lib/kobject_uevent.c:608 loop_set_size drivers/block/loop.c:211 [inline] loop_set_size drivers/block/loop.c:208 [inline] loop_set_status+0x9c9/0xb90 drivers/block/loop.c:1254 loop_set_status_old+0x162/0x1d0 drivers/block/loop.c:1353 lo_ioctl+0xb3f/0x2760 drivers/block/loop.c:1523 blkdev_ioctl+0x277/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:893 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: 0033:0x7f652e78e929 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:00007f652f6ab038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f652e9b5fa0 RCX: 00007f652e78e929 RDX: 00002000000001c0 RSI: 0000000000004c02 RDI: 0000000000000003 RBP: 00007f652e810b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f652e9b5fa0 R15: 00007fff8c5fc538