loop0: detected capacity change from 32768 to 0 ====================================================== WARNING: possible circular locking dependency detected 6.15.0-syzkaller-gfeacb1774bd5 #0 Not tainted ------------------------------------------------------ syz.0.16/6085 is trying to acquire lock: ffffffff8f868d28 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffffffff8f868d28 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410 but task is already holding lock: ffff8880340d9e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] ffff8880340d9e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: loop_set_status+0x225/0xaf0 drivers/block/loop.c:1235 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#17){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4396 [inline] __blk_mq_alloc_disk+0x162/0x340 block/blk-mq.c:4443 loop_add+0x419/0xad0 drivers/block/loop.c:2010 loop_init+0x173/0x230 drivers/block/loop.c:2245 do_one_initcall+0x233/0x820 init/main.c:1257 do_initcall_level+0x137/0x1f0 init/main.c:1319 do_initcalls+0x69/0xd0 init/main.c:1335 kernel_init_freeable+0x3d9/0x570 init/main.c:1567 kernel_init+0x1d/0x1d0 init/main.c:1457 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __fs_reclaim_acquire mm/page_alloc.c:4060 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4074 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4098 [inline] slab_alloc_node mm/slub.c:4176 [inline] kmem_cache_alloc_node_noprof+0x47/0x3c0 mm/slub.c:4248 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:658 alloc_skb include/linux/skbuff.h:1340 [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+0x55b/0x8c0 lib/kobject_uevent.c:608 kobject_synth_uevent+0x527/0xb00 lib/kobject_uevent.c:207 bus_uevent_store+0x115/0x170 drivers/base/bus.c:832 kernfs_fop_write_iter+0x375/0x4f0 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x54b/0xa90 fs/read_write.c:686 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 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+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410 kobject_uevent_env+0x55b/0x8c0 lib/kobject_uevent.c:608 loop_set_size drivers/block/loop.c:211 [inline] loop_set_status+0x4d1/0xaf0 drivers/block/loop.c:1250 lo_ioctl+0xa58/0x2400 drivers/block/loop.c:-1 blkdev_ioctl+0x5a5/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 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)#17 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#17); lock(fs_reclaim); lock(&q->q_usage_counter(io)#17); lock(uevent_sock_mutex); *** DEADLOCK *** 3 locks held by syz.0.16/6085: #0: ffff888000b9c400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2a/0xaf0 drivers/block/loop.c:1219 #1: ffff8880340d9e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] #1: ffff8880340d9e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: loop_set_status+0x225/0xaf0 drivers/block/loop.c:1235 #2: ffff8880340d9e38 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] #2: ffff8880340d9e38 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: loop_set_status+0x225/0xaf0 drivers/block/loop.c:1235 stack backtrace: CPU: 0 UID: 0 PID: 6085 Comm: syz.0.16 Not tainted 6.15.0-syzkaller-gfeacb1774bd5 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410 kobject_uevent_env+0x55b/0x8c0 lib/kobject_uevent.c:608 loop_set_size drivers/block/loop.c:211 [inline] loop_set_status+0x4d1/0xaf0 drivers/block/loop.c:1250 lo_ioctl+0xa58/0x2400 drivers/block/loop.c:-1 blkdev_ioctl+0x5a5/0x6d0 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd3a0f8d169 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:00007fd3a1d75038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fd3a11a5fa0 RCX: 00007fd3a0f8d169 RDX: 0000400000000580 RSI: 0000000000004c02 RDI: 0000000000000005 RBP: 00007fd3a100e2a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fd3a11a5fa0 R15: 00007ffc8cd54968