loop7: detected capacity change from 16384 to 0 ====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc5-syzkaller-00300-g3ce9925823c7 #0 Not tainted ------------------------------------------------------ syz.2.1913/12540 is trying to acquire lock: ffffffff8f657c48 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffffffff8f657c48 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x27e/0x560 lib/kobject_uevent.c:410 but task is already holding lock: ffff8880243a6228 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:928 [inline] ffff8880243a6228 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_set_status+0x225/0xaf0 drivers/block/loop.c:1238 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#24){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4348 [inline] __blk_mq_alloc_disk+0x164/0x350 block/blk-mq.c:4395 loop_add+0x41d/0xae0 drivers/block/loop.c:2013 loop_init+0x173/0x230 drivers/block/loop.c:2248 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+0x4b/0x80 arch/x86/kernel/process.c:153 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:5866 __fs_reclaim_acquire mm/page_alloc.c:4064 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4078 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:591 [inline] vfs_write+0x548/0xa90 fs/read_write.c:684 ksys_write+0x145/0x250 fs/read_write.c:736 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf6/0x210 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:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 __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:1253 loop_set_status_compat drivers/block/loop.c:1629 [inline] lo_compat_ioctl+0x273/0x330 drivers/block/loop.c:1655 compat_blkdev_ioctl+0x5ce/0x780 block/ioctl.c:760 __do_compat_sys_ioctl fs/ioctl.c:1004 [inline] __se_compat_sys_ioctl fs/ioctl.c:947 [inline] __ia32_compat_sys_ioctl+0x551/0x840 fs/ioctl.c:947 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xb4/0x110 arch/x86/entry/syscall_32.c:306 do_fast_syscall_32+0x34/0x80 arch/x86/entry/syscall_32.c:331 entry_SYSENTER_compat_after_hwframe+0x84/0x8e other info that might help us debug this: Chain exists of: uevent_sock_mutex --> fs_reclaim --> &q->q_usage_counter(io)#24 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#24); lock(fs_reclaim); lock(&q->q_usage_counter(io)#24); lock(uevent_sock_mutex); *** DEADLOCK *** 3 locks held by syz.2.1913/12540: #0: ffff8880243d3368 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2a/0xaf0 drivers/block/loop.c:1222 #1: ffff8880243a6228 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:928 [inline] #1: ffff8880243a6228 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_set_status+0x225/0xaf0 drivers/block/loop.c:1238 #2: ffff8880243a6260 (&q->q_usage_counter(queue)#19){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:928 [inline] #2: ffff8880243a6260 (&q->q_usage_counter(queue)#19){+.+.}-{0:0}, at: loop_set_status+0x225/0xaf0 drivers/block/loop.c:1238 stack backtrace: CPU: 0 UID: 0 PID: 12540 Comm: syz.2.1913 Not tainted 6.15.0-rc5-syzkaller-00300-g3ce9925823c7 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211 check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866 __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:1253 loop_set_status_compat drivers/block/loop.c:1629 [inline] lo_compat_ioctl+0x273/0x330 drivers/block/loop.c:1655 compat_blkdev_ioctl+0x5ce/0x780 block/ioctl.c:760 __do_compat_sys_ioctl fs/ioctl.c:1004 [inline] __se_compat_sys_ioctl fs/ioctl.c:947 [inline] __ia32_compat_sys_ioctl+0x551/0x840 fs/ioctl.c:947 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xb4/0x110 arch/x86/entry/syscall_32.c:306 do_fast_syscall_32+0x34/0x80 arch/x86/entry/syscall_32.c:331 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf70de539 Code: 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 002b:00000000f508c55c EFLAGS: 00000206 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000004c02 RDX: 00000000800001c0 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ---------------- Code disassembly (best guess): 0: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi 4: 10 07 adc %al,(%rdi) 6: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi a: 10 08 adc %cl,(%rax) c: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi 20: 00 51 52 add %dl,0x52(%rcx) 23: 55 push %rbp 24: 89 e5 mov %esp,%ebp 26: 0f 34 sysenter 28: cd 80 int $0x80 * 2a: 5d pop %rbp <-- trapping instruction 2b: 5a pop %rdx 2c: 59 pop %rcx 2d: c3 ret 2e: 90 nop 2f: 90 nop 30: 90 nop 31: 90 nop 32: 90 nop 33: 90 nop 34: 90 nop 35: 90 nop 36: 90 nop 37: 90 nop 38: 90 nop 39: 90 nop 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 90 nop 3f: 90 nop