====================================================== WARNING: possible circular locking dependency detected 6.16.0-syzkaller-11952-g6e64f4580381 #0 Not tainted ------------------------------------------------------ syz.0.1088/8696 is trying to acquire lock: ffff88801b2ffa20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x9e/0x450 fs/kernfs/inode.c:193 but task is already holding lock: ffff8880248762c8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] ffff8880248762c8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:584 [inline] ffff8880248762c8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: lo_ioctl+0x17f2/0x1d00 drivers/block/loop.c:1534 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:5868 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4400 [inline] __blk_mq_alloc_disk+0x15c/0x340 block/blk-mq.c:4447 loop_add+0x411/0xad0 drivers/block/loop.c:2034 loop_init+0xd9/0x170 drivers/block/loop.c:2269 do_one_initcall+0x233/0x820 init/main.c:1269 do_initcall_level+0x104/0x190 init/main.c:1331 do_initcalls+0x59/0xa0 init/main.c:1347 kernel_init_freeable+0x334/0x4b0 init/main.c:1579 kernel_init+0x1d/0x1d0 init/main.c:1469 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:5868 __fs_reclaim_acquire mm/page_alloc.c:4234 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4248 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4131 [inline] slab_alloc_node mm/slub.c:4209 [inline] kmem_cache_alloc_noprof+0x44/0x3c0 mm/slub.c:4236 __kernfs_iattrs+0xd9/0x320 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+0xb33/0xe40 fs/attr.c:552 do_truncate+0x1a4/0x220 fs/open.c:68 handle_truncate fs/namei.c:3508 [inline] do_open fs/namei.c:3891 [inline] path_openat+0x306c/0x3830 fs/namei.c:4046 do_filp_open+0x1fa/0x410 fs/namei.c:4073 do_sys_openat2+0x121/0x1c0 fs/open.c:1435 do_sys_open fs/open.c:1450 [inline] __do_sys_openat fs/open.c:1466 [inline] __se_sys_openat fs/open.c:1461 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1461 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 (&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+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read+0x46/0x2e0 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:455 [inline] loop_assign_backing_file+0x222/0x400 drivers/block/loop.c:508 loop_change_fd drivers/block/loop.c:586 [inline] lo_ioctl+0x1860/0x1d00 drivers/block/loop.c:1534 lo_compat_ioctl+0x298/0x330 drivers/block/loop.c:1694 compat_blkdev_ioctl+0x5d1/0x780 block/ioctl.c:761 __do_compat_sys_ioctl fs/ioctl.c:696 [inline] __se_compat_sys_ioctl fs/ioctl.c:639 [inline] __ia32_compat_sys_ioctl+0x540/0x840 fs/ioctl.c:639 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xb6/0x2b0 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: &root->kernfs_iattr_rwsem --> 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); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz.0.1088/8696: #0: ffff88814373f400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline] #0: ffff88814373f400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_change_fd drivers/block/loop.c:551 [inline] #0: ffff88814373f400 (&lo->lo_mutex){+.+.}-{4:4}, at: lo_ioctl+0xfbf/0x1d00 drivers/block/loop.c:1534 #1: ffff8880248762c8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] #1: ffff8880248762c8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:584 [inline] #1: ffff8880248762c8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: lo_ioctl+0x17f2/0x1d00 drivers/block/loop.c:1534 #2: ffff888024876300 (&q->q_usage_counter(queue)#19){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:934 [inline] #2: ffff888024876300 (&q->q_usage_counter(queue)#19){+.+.}-{0:0}, at: loop_change_fd drivers/block/loop.c:584 [inline] #2: ffff888024876300 (&q->q_usage_counter(queue)#19){+.+.}-{0:0}, at: lo_ioctl+0x17f2/0x1d00 drivers/block/loop.c:1534 stack backtrace: CPU: 1 UID: 0 PID: 8696 Comm: syz.0.1088 Not tainted 6.16.0-syzkaller-11952-g6e64f4580381 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read+0x46/0x2e0 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:455 [inline] loop_assign_backing_file+0x222/0x400 drivers/block/loop.c:508 loop_change_fd drivers/block/loop.c:586 [inline] lo_ioctl+0x1860/0x1d00 drivers/block/loop.c:1534 lo_compat_ioctl+0x298/0x330 drivers/block/loop.c:1694 compat_blkdev_ioctl+0x5d1/0x780 block/ioctl.c:761 __do_compat_sys_ioctl fs/ioctl.c:696 [inline] __se_compat_sys_ioctl fs/ioctl.c:639 [inline] __ia32_compat_sys_ioctl+0x540/0x840 fs/ioctl.c:639 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xb6/0x2b0 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: 0023:0xf708e539 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:00000000f545d55c EFLAGS: 00000206 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004c06 RDX: 0000000000000004 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