====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc1-syzkaller-00139-gab59a8605604 #0 Not tainted ------------------------------------------------------ syz.0.842/8718 is trying to acquire lock: ffff88801bef79e0 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0xb3/0x510 fs/kernfs/inode.c:191 but task is already holding lock: ffff888143b4f5a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:928 [inline] ffff888143b4f5a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:643 [inline] ffff888143b4f5a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: lo_ioctl+0x203b/0x2850 drivers/block/loop.c:1569 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&q->q_usage_counter(io)#26){++++}-{0:0}: lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 blk_alloc_queue+0x542/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4348 [inline] __blk_mq_alloc_disk+0x162/0x380 block/blk-mq.c:4395 loop_add+0x445/0xaf0 drivers/block/loop.c:2067 loop_init+0x168/0x220 drivers/block/loop.c:2302 do_one_initcall+0x24a/0x940 init/main.c:1257 do_initcall_level+0x157/0x210 init/main.c:1319 do_initcalls+0x71/0xd0 init/main.c:1335 kernel_init_freeable+0x432/0x5d0 init/main.c:1567 kernel_init+0x1d/0x2b0 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 -> #2 (fs_reclaim){+.+.}-{0:0}: lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 __fs_reclaim_acquire mm/page_alloc.c:4028 [inline] fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:4042 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4102 [inline] slab_alloc_node mm/slub.c:4180 [inline] kmem_cache_alloc_noprof+0x49/0x390 mm/slub.c:4207 __kernfs_iattrs+0x94/0x280 fs/kernfs/inode.c:37 kernfs_iattrs fs/kernfs/inode.c:60 [inline] __kernfs_setattr fs/kernfs/inode.c:73 [inline] kernfs_iop_setattr+0xe3/0x3f0 fs/kernfs/inode.c:127 notify_change+0xbca/0xe90 fs/attr.c:552 do_truncate+0x222/0x310 fs/open.c:65 handle_truncate fs/namei.c:3466 [inline] do_open fs/namei.c:3849 [inline] path_openat+0x2e4f/0x35d0 fs/namei.c:4004 do_filp_open+0x284/0x4e0 fs/namei.c:4031 do_sys_openat2+0x12b/0x1d0 fs/open.c:1429 do_sys_open fs/open.c:1444 [inline] __do_sys_openat fs/open.c:1460 [inline] __se_sys_openat fs/open.c:1455 [inline] __x64_sys_openat+0x249/0x2a0 fs/open.c:1455 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (iattr_mutex){+.+.}-{4:4}: lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746 __kernfs_iattrs+0x2b/0x280 fs/kernfs/inode.c:32 kernfs_iattrs fs/kernfs/inode.c:60 [inline] __kernfs_setattr fs/kernfs/inode.c:73 [inline] kernfs_iop_setattr+0xe3/0x3f0 fs/kernfs/inode.c:127 notify_change+0xbca/0xe90 fs/attr.c:552 do_truncate+0x222/0x310 fs/open.c:65 handle_truncate fs/namei.c:3466 [inline] do_open fs/namei.c:3849 [inline] path_openat+0x2e4f/0x35d0 fs/namei.c:4004 do_filp_open+0x284/0x4e0 fs/namei.c:4031 do_sys_openat2+0x12b/0x1d0 fs/open.c:1429 do_sys_open fs/open.c:1444 [inline] __do_sys_openat fs/open.c:1460 [inline] __se_sys_openat fs/open.c:1455 [inline] __x64_sys_openat+0x249/0x2a0 fs/open.c:1455 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 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:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain+0xa69/0x24e0 kernel/locking/lockdep.c:3909 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 down_read+0xb3/0xa50 kernel/locking/rwsem.c:1524 kernfs_iop_getattr+0xb3/0x510 fs/kernfs/inode.c:191 loop_query_min_dio_size drivers/block/loop.c:529 [inline] loop_assign_backing_file+0x276/0x500 drivers/block/loop.c:582 loop_change_fd drivers/block/loop.c:645 [inline] lo_ioctl+0x20a9/0x2850 drivers/block/loop.c:1569 blkdev_ioctl+0x5df/0x710 block/ioctl.c:698 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 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)#26 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#26); lock(fs_reclaim); lock(&q->q_usage_counter(io)#26); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz.0.842/8718: #0: ffff88802580f368 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline] #0: ffff88802580f368 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_change_fd drivers/block/loop.c:610 [inline] #0: ffff88802580f368 (&lo->lo_mutex){+.+.}-{4:4}, at: lo_ioctl+0x135f/0x2850 drivers/block/loop.c:1569 #1: ffff888143b4f5a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:928 [inline] #1: ffff888143b4f5a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:643 [inline] #1: ffff888143b4f5a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: lo_ioctl+0x203b/0x2850 drivers/block/loop.c:1569 #2: ffff888143b4f5e0 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:928 [inline] #2: ffff888143b4f5e0 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: loop_change_fd drivers/block/loop.c:643 [inline] #2: ffff888143b4f5e0 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: lo_ioctl+0x203b/0x2850 drivers/block/loop.c:1569 stack backtrace: CPU: 1 UID: 0 PID: 8718 Comm: syz.0.842 Not tainted 6.15.0-rc1-syzkaller-00139-gab59a8605604 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2079 check_noncircular+0x142/0x160 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+0xa69/0x24e0 kernel/locking/lockdep.c:3909 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866 down_read+0xb3/0xa50 kernel/locking/rwsem.c:1524 kernfs_iop_getattr+0xb3/0x510 fs/kernfs/inode.c:191 loop_query_min_dio_size drivers/block/loop.c:529 [inline] loop_assign_backing_file+0x276/0x500 drivers/block/loop.c:582 loop_change_fd drivers/block/loop.c:645 [inline] lo_ioctl+0x20a9/0x2850 drivers/block/loop.c:1569 blkdev_ioctl+0x5df/0x710 block/ioctl.c:698 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9de678d169 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f9de75f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f9de69a5fa0 RCX: 00007f9de678d169 RDX: 0000000000000004 RSI: 0000000000004c06 RDI: 0000000000000003 RBP: 00007f9de680e990 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f9de69a5fa0 R15: 00007f9de6acfa28