loop6: detected capacity change from 0 to 524287999 loop6: detected capacity change from 524287999 to 524288000 ====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc1-syzkaller-g39dfc971e42d #0 Not tainted ------------------------------------------------------ syz.4.593/9647 is trying to acquire lock: ffff800092bd96e8 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffff800092bd96e8 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x24c/0x548 lib/kobject_uevent.c:410 but task is already holding lock: ffff0000c9edbb28 (&q->q_usage_counter(io)#23){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] ffff0000c9edbb28 (&q->q_usage_counter(io)#23){++++}-{0:0}, at: loop_set_status+0x1d4/0x9e0 drivers/block/loop.c:1239 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#23){++++}-{0:0}: blk_alloc_queue+0x48c/0x54c block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4396 [inline] __blk_mq_alloc_disk+0x12c/0x310 block/blk-mq.c:4443 loop_add+0x32c/0x88c drivers/block/loop.c:2014 loop_init+0x168/0x1a0 drivers/block/loop.c:2249 do_one_initcall+0x250/0x990 init/main.c:1273 do_initcall_level+0x154/0x214 init/main.c:1335 do_initcalls+0x84/0xf4 init/main.c:1351 do_basic_setup+0x8c/0xa0 init/main.c:1370 kernel_init_freeable+0x2dc/0x444 init/main.c:1583 kernel_init+0x24/0x1dc init/main.c:1473 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4045 [inline] fs_reclaim_acquire+0x8c/0x118 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+0x60/0x3f4 mm/slub.c:4249 __alloc_skb+0x144/0x2ec net/core/skbuff.c:660 alloc_skb include/linux/skbuff.h:1336 [inline] alloc_uevent_skb+0x78/0x1e0 lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x2d4/0x548 lib/kobject_uevent.c:410 kobject_uevent_env+0x528/0x884 lib/kobject_uevent.c:608 kobject_synth_uevent+0x82c/0xa74 lib/kobject_uevent.c:207 bus_uevent_store+0x114/0x16c drivers/base/bus.c:832 bus_attr_store+0x80/0xa4 drivers/base/bus.c:172 sysfs_kf_write+0x1a8/0x23c fs/sysfs/file.c:145 kernfs_fop_write_iter+0x314/0x488 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x62c/0x97c fs/read_write.c:686 ksys_write+0x120/0x210 fs/read_write.c:738 __do_sys_write fs/read_write.c:749 [inline] __se_sys_write fs/read_write.c:746 [inline] __arm64_sys_write+0x7c/0x90 fs/read_write.c:746 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 -> #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+0x1774/0x30a4 kernel/locking/lockdep.c:5240 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871 __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:799 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x24c/0x548 lib/kobject_uevent.c:410 kobject_uevent_env+0x528/0x884 lib/kobject_uevent.c:608 set_capacity_and_notify+0x22c/0x290 block/genhd.c:102 loop_set_size drivers/block/loop.c:210 [inline] loop_set_status+0x3f0/0x9e0 drivers/block/loop.c:1254 lo_ioctl+0x7f0/0x1b8c drivers/block/loop.c:-1 blkdev_ioctl+0x610/0xac0 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] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:893 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 other info that might help us debug this: Chain exists of: uevent_sock_mutex --> fs_reclaim --> &q->q_usage_counter(io)#23 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#23); lock(fs_reclaim); lock(&q->q_usage_counter(io)#23); lock(uevent_sock_mutex); *** DEADLOCK *** 3 locks held by syz.4.593/9647: #0: ffff0000c9f68400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x40/0x9e0 drivers/block/loop.c:1223 #1: ffff0000c9edbb28 (&q->q_usage_counter(io)#23){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] #1: ffff0000c9edbb28 (&q->q_usage_counter(io)#23){++++}-{0:0}, at: loop_set_status+0x1d4/0x9e0 drivers/block/loop.c:1239 #2: ffff0000c9edbb60 (&q->q_usage_counter(queue)#22){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] #2: ffff0000c9edbb60 (&q->q_usage_counter(queue)#22){+.+.}-{0:0}, at: loop_set_status+0x1d4/0x9e0 drivers/block/loop.c:1239 stack backtrace: CPU: 0 UID: 0 PID: 9647 Comm: syz.4.593 Not tainted 6.16.0-rc1-syzkaller-g39dfc971e42d #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2046 check_noncircular+0x154/0x174 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+0x1774/0x30a4 kernel/locking/lockdep.c:5240 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5871 __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:602 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:799 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x24c/0x548 lib/kobject_uevent.c:410 kobject_uevent_env+0x528/0x884 lib/kobject_uevent.c:608 set_capacity_and_notify+0x22c/0x290 block/genhd.c:102 loop_set_size drivers/block/loop.c:210 [inline] loop_set_status+0x3f0/0x9e0 drivers/block/loop.c:1254 lo_ioctl+0x7f0/0x1b8c drivers/block/loop.c:-1 blkdev_ioctl+0x610/0xac0 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] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:893 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x58/0x17c arch/arm64/kernel/entry-common.c:767 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 loop4: detected capacity change from 0 to 4096