====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.4.127/6266 is trying to acquire lock: ffff88801b6c5a20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x9e/0x450 fs/kernfs/inode.c:193 but task is already holding lock: ffff88802566f2c0 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline] ffff88802566f2c0 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] ffff88802566f2c0 (&q->q_usage_counter(io)#24){++++}-{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)#24){++++}-{0:0}: blk_alloc_queue+0x546/0x680 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4432 [inline] __blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4479 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+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4336 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4350 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4410 [inline] slab_alloc_node mm/slub.c:4765 [inline] kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4795 __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:4279 [inline] do_open fs/namei.c:4675 [inline] path_openat+0x2f89/0x3860 fs/namei.c:4830 do_file_open+0x23e/0x4a0 fs/namei.c:4859 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/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 lo_compat_ioctl+0x324/0x3f0 drivers/block/loop.c:1706 compat_blkdev_ioctl+0x5ea/0x7c0 block/ioctl.c:848 __do_compat_sys_ioctl fs/ioctl.c:695 [inline] __se_compat_sys_ioctl fs/ioctl.c:638 [inline] __ia32_compat_sys_ioctl+0x5ea/0x950 fs/ioctl.c:638 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x20d/0x640 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332 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.4.127/6266: #0: ffff8880259e6448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline] #0: ffff8880259e6448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_change_fd drivers/block/loop.c:562 [inline] #0: ffff8880259e6448 (&lo->lo_mutex){+.+.}-{4:4}, at: lo_ioctl+0x14c7/0x1fb0 drivers/block/loop.c:1546 #1: ffff88802566f2c0 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline] #1: ffff88802566f2c0 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] #1: ffff88802566f2c0 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: lo_ioctl+0x1a51/0x1fb0 drivers/block/loop.c:1546 #2: ffff88802566f2f8 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline] #2: ffff88802566f2f8 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] #2: ffff88802566f2f8 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: lo_ioctl+0x1a51/0x1fb0 drivers/block/loop.c:1546 stack backtrace: CPU: 0 UID: 0 PID: 6266 Comm: syz.4.127 Not tainted syzkaller #0 PREEMPT(full) 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 lo_compat_ioctl+0x324/0x3f0 drivers/block/loop.c:1706 compat_blkdev_ioctl+0x5ea/0x7c0 block/ioctl.c:848 __do_compat_sys_ioctl fs/ioctl.c:695 [inline] __se_compat_sys_ioctl fs/ioctl.c:638 [inline] __ia32_compat_sys_ioctl+0x5ea/0x950 fs/ioctl.c:638 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x20d/0x640 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf7f46f6c Code: 90 85 d2 74 0a 89 ce 81 e6 ff 0f 00 00 89 32 85 c0 74 05 c1 e9 0c 89 08 31 c0 5e 5d c3 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 58 b8 77 00 00 00 cd 80 0f 0b 90 90 90 90 90 90 b8 ad RSP: 002b:00000000f540650c EFLAGS: 00000206 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000004c06 RDX: 0000000000000005 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: 90 nop 1: 85 d2 test %edx,%edx 3: 74 0a je 0xf 5: 89 ce mov %ecx,%esi 7: 81 e6 ff 0f 00 00 and $0xfff,%esi d: 89 32 mov %esi,(%rdx) f: 85 c0 test %eax,%eax 11: 74 05 je 0x18 13: c1 e9 0c shr $0xc,%ecx 16: 89 08 mov %ecx,(%rax) 18: 31 c0 xor %eax,%eax 1a: 5e pop %rsi 1b: 5d pop %rbp 1c: c3 ret 1d: 90 nop 1e: 0f 1f 00 nopl (%rax) 21: 51 push %rcx 22: 52 push %rdx 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: 58 pop %rax 2f: b8 77 00 00 00 mov $0x77,%eax 34: cd 80 int $0x80 36: 0f 0b ud2 38: 90 nop 39: 90 nop 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: b8 .byte 0xb8 3f: ad lods %ds:(%rsi),%eax