====================================================== WARNING: possible circular locking dependency detected 6.14.0-rc2-syzkaller #0 Not tainted ------------------------------------------------------ syz.3.16/3542 is trying to acquire lock: ffffffff837ff0f8 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffffffff837ff0f8 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x12b/0x230 lib/kobject_uevent.c:410 but task is already holding lock: ffff88810969c0c0 (&q->q_usage_counter(io)#8){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:910 [inline] ffff88810969c0c0 (&q->q_usage_counter(io)#8){++++}-{0:0}, at: loop_set_status+0x97/0x280 drivers/block/loop.c:1283 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#8){++++}-{0:0}: blk_alloc_queue+0x33f/0x370 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4349 [inline] __blk_mq_alloc_disk+0x74/0x120 block/blk-mq.c:4396 loop_add+0x1d4/0x3d0 drivers/block/loop.c:2059 loop_init+0xc2/0xe0 drivers/block/loop.c:2294 do_one_initcall+0xe3/0x380 init/main.c:1257 do_initcall_level+0x8f/0x100 init/main.c:1319 do_initcalls+0x54/0x90 init/main.c:1335 kernel_init_freeable+0x183/0x200 init/main.c:1568 kernel_init+0x15/0x120 init/main.c:1457 ret_from_fork+0x32/0x40 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:3853 [inline] fs_reclaim_acquire+0x51/0xc0 mm/page_alloc.c:3867 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4066 [inline] slab_alloc_node mm/slub.c:4144 [inline] kmem_cache_alloc_node_noprof+0x49/0x3f0 mm/slub.c:4216 __alloc_skb+0x92/0x210 net/core/skbuff.c:668 alloc_skb include/linux/skbuff.h:1331 [inline] alloc_uevent_skb+0x44/0xc0 lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x18e/0x230 lib/kobject_uevent.c:410 kobject_uevent_env+0x318/0x400 lib/kobject_uevent.c:608 kobject_synth_uevent+0x414/0x470 lib/kobject_uevent.c:207 bus_uevent_store+0x97/0xd0 drivers/base/bus.c:832 kernfs_fop_write_iter+0x11f/0x1a0 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:586 [inline] vfs_write+0x28f/0x350 fs/read_write.c:679 ksys_write+0x75/0xf0 fs/read_write.c:731 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xa4/0x180 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (uevent_sock_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3163 [inline] check_prevs_add kernel/locking/lockdep.c:3282 [inline] validate_chain kernel/locking/lockdep.c:3906 [inline] __lock_acquire+0x12cb/0x20e0 kernel/locking/lockdep.c:5228 lock_acquire+0xea/0x270 kernel/locking/lockdep.c:5851 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0xac/0xa90 kernel/locking/mutex.c:730 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x12b/0x230 lib/kobject_uevent.c:410 kobject_uevent_env+0x318/0x400 lib/kobject_uevent.c:608 loop_set_size drivers/block/loop.c:217 [inline] loop_set_status+0x14c/0x280 drivers/block/loop.c:1298 lo_ioctl+0x64d/0xa80 drivers/block/loop.c:-1 blkdev_ioctl+0x2c4/0x310 block/ioctl.c:698 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0x69/0xc0 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xa4/0x180 arch/x86/entry/common.c:83 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)#8 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#8); lock(fs_reclaim); lock(&q->q_usage_counter(io)#8); lock(uevent_sock_mutex); *** DEADLOCK *** 3 locks held by syz.3.16/3542: #0: ffff8881096ea368 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x22/0x280 drivers/block/loop.c:1267 #1: ffff88810969c0c0 (&q->q_usage_counter(io)#8){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:910 [inline] #1: ffff88810969c0c0 (&q->q_usage_counter(io)#8){++++}-{0:0}, at: loop_set_status+0x97/0x280 drivers/block/loop.c:1283 #2: ffff88810969c0f8 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:910 [inline] #2: ffff88810969c0f8 (&q->q_usage_counter(queue)#2){+.+.}-{0:0}, at: loop_set_status+0x97/0x280 drivers/block/loop.c:1283 stack backtrace: CPU: 0 UID: 0 PID: 3542 Comm: syz.3.16 Not tainted 6.14.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025 Call Trace: dump_stack_lvl+0xaf/0x110 lib/dump_stack.c:120 print_circular_bug+0x29b/0x2b0 kernel/locking/lockdep.c:2076 check_noncircular+0x110/0x130 kernel/locking/lockdep.c:2208 check_prev_add kernel/locking/lockdep.c:3163 [inline] check_prevs_add kernel/locking/lockdep.c:3282 [inline] validate_chain kernel/locking/lockdep.c:3906 [inline] __lock_acquire+0x12cb/0x20e0 kernel/locking/lockdep.c:5228 lock_acquire+0xea/0x270 kernel/locking/lockdep.c:5851 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0xac/0xa90 kernel/locking/mutex.c:730 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x12b/0x230 lib/kobject_uevent.c:410 kobject_uevent_env+0x318/0x400 lib/kobject_uevent.c:608 loop_set_size drivers/block/loop.c:217 [inline] loop_set_status+0x14c/0x280 drivers/block/loop.c:1298 lo_ioctl+0x64d/0xa80 drivers/block/loop.c:-1 blkdev_ioctl+0x2c4/0x310 block/ioctl.c:698 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0x69/0xc0 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xa4/0x180 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f01fa98e969 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:00007f01fb8db038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f01fabb5fa0 RCX: 00007f01fa98e969 RDX: 00002000000001c0 RSI: 0000000000004c02 RDI: 0000000000000003 RBP: 00007f01faa10ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f01fabb5fa0 R15: 00007ffc6d2b8ef8