====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.6.4770/28293 is trying to acquire lock: ffff888026c94220 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x9e/0x450 fs/kernfs/inode.c:193 but task is already holding lock: ffff888024e73008 (&q->q_usage_counter(io)#21){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:954 [inline] ffff888024e73008 (&q->q_usage_counter(io)#21){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] ffff888024e73008 (&q->q_usage_counter(io)#21){++++}-{0:0}, at: lo_ioctl+0x1a51/0x1fb0 drivers/block/loop.c:1546 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#21){++++}-{0:0}: blk_alloc_queue+0x52f/0x610 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4415 [inline] __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4462 loop_add+0x482/0xb40 drivers/block/loop.c:2050 loop_init+0xd9/0x170 drivers/block/loop.c:2289 do_one_initcall+0x250/0x840 init/main.c:1378 do_initcall_level+0x104/0x190 init/main.c:1440 do_initcalls+0x59/0xa0 init/main.c:1456 kernel_init_freeable+0x2a6/0x3d0 init/main.c:1688 kernel_init+0x1d/0x1d0 init/main.c:1578 ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4331 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4345 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4904 [inline] slab_alloc_node mm/slub.c:5239 [inline] kmem_cache_alloc_noprof+0x45/0x6e0 mm/slub.c:5270 __kernfs_iattrs+0xdf/0x340 fs/kernfs/inode.c:36 kernfs_iattrs fs/kernfs/inode.c:61 [inline] __kernfs_setattr fs/kernfs/inode.c:74 [inline] kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:128 notify_change+0xc1a/0xf40 fs/attr.c:546 do_truncate+0x1c2/0x250 fs/open.c:68 handle_truncate fs/namei.c:4244 [inline] do_open fs/namei.c:4641 [inline] path_openat+0x360c/0x3e20 fs/namei.c:4796 do_filp_open+0x22d/0x490 fs/namei.c:4823 do_sys_openat2+0x12f/0x220 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&root->kernfs_iattr_rwsem){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868 down_read+0x47/0x2e0 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0x9e/0x450 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x2e1/0x430 fs/stat.c:213 loop_query_min_dio_size drivers/block/loop.c:464 [inline] loop_assign_backing_file+0x27a/0x4b0 drivers/block/loop.c:517 loop_change_fd drivers/block/loop.c:597 [inline] lo_ioctl+0x1acb/0x1fb0 drivers/block/loop.c:1546 blkdev_ioctl+0x5e3/0x740 block/ioctl.c:792 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 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: &root->kernfs_iattr_rwsem --> fs_reclaim --> &q->q_usage_counter(io)#21 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#21); lock(fs_reclaim); lock(&q->q_usage_counter(io)#21); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz.6.4770/28293: #0: ffff888141f6e448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline] #0: ffff888141f6e448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_change_fd drivers/block/loop.c:562 [inline] #0: ffff888141f6e448 (&lo->lo_mutex){+.+.}-{4:4}, at: lo_ioctl+0x14c7/0x1fb0 drivers/block/loop.c:1546 #1: ffff888024e73008 (&q->q_usage_counter(io)#21){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:954 [inline] #1: ffff888024e73008 (&q->q_usage_counter(io)#21){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] #1: ffff888024e73008 (&q->q_usage_counter(io)#21){++++}-{0:0}, at: lo_ioctl+0x1a51/0x1fb0 drivers/block/loop.c:1546 #2: ffff888024e73040 (&q->q_usage_counter(queue)#5){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:954 [inline] #2: ffff888024e73040 (&q->q_usage_counter(queue)#5){+.+.}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] #2: ffff888024e73040 (&q->q_usage_counter(queue)#5){+.+.}-{0:0}, at: lo_ioctl+0x1a51/0x1fb0 drivers/block/loop.c:1546 stack backtrace: CPU: 0 UID: 0 PID: 28293 Comm: syz.6.4770 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868 down_read+0x47/0x2e0 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0x9e/0x450 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x2e1/0x430 fs/stat.c:213 loop_query_min_dio_size drivers/block/loop.c:464 [inline] loop_assign_backing_file+0x27a/0x4b0 drivers/block/loop.c:517 loop_change_fd drivers/block/loop.c:597 [inline] lo_ioctl+0x1acb/0x1fb0 drivers/block/loop.c:1546 blkdev_ioctl+0x5e3/0x740 block/ioctl.c:792 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f226839aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f2269271028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f2268615fa0 RCX: 00007f226839aeb9 RDX: 0000000000000007 RSI: 0000000000004c06 RDI: 0000000000000006 RBP: 00007f2268408c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f2268616038 R14: 00007f2268615fa0 R15: 00007f226873fa48