====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.1.80/7108 is trying to acquire lock: ffff0000c1844220 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0xa0/0x410 fs/kernfs/inode.c:193 but task is already holding lock: ffff0000cb935f60 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:954 [inline] ffff0000cb935f60 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] ffff0000cb935f60 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: lo_ioctl+0x11e0/0x177c 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+0x48c/0x54c block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4415 [inline] __blk_mq_alloc_disk+0x124/0x304 block/blk-mq.c:4462 loop_add+0x324/0x880 drivers/block/loop.c:2050 loop_init+0xe8/0x10c drivers/block/loop.c:2285 do_one_initcall+0x248/0x9b4 init/main.c:1378 do_initcall_level+0x128/0x1c4 init/main.c:1440 do_initcalls+0x70/0xd0 init/main.c:1456 do_basic_setup+0x78/0x8c init/main.c:1475 kernel_init_freeable+0x268/0x39c init/main.c:1688 kernel_init+0x24/0x1dc init/main.c:1578 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4301 [inline] fs_reclaim_acquire+0x8c/0x118 mm/page_alloc.c:4315 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+0x5c/0x680 mm/slub.c:5270 __kernfs_iattrs+0xd4/0x2d8 fs/kernfs/inode.c:36 kernfs_iattrs fs/kernfs/inode.c:61 [inline] __kernfs_setattr fs/kernfs/inode.c:74 [inline] kernfs_iop_setattr+0xdc/0x374 fs/kernfs/inode.c:128 notify_change+0xa0c/0xcb8 fs/attr.c:546 do_truncate+0x198/0x210 fs/open.c:68 handle_truncate fs/namei.c:4235 [inline] do_open fs/namei.c:4632 [inline] path_openat+0x2a08/0x3114 fs/namei.c:4787 do_filp_open+0x18c/0x36c fs/namei.c:4814 do_sys_openat2+0x11c/0x1f0 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] __arm64_sys_openat+0x120/0x158 fs/open.c:1447 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #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+0x1774/0x30a4 kernel/locking/lockdep.c:5237 lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868 down_read+0x58/0x308 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0xa0/0x410 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x254/0x38c fs/stat.c:213 vfs_getattr+0x60/0x84 fs/stat.c:262 loop_query_min_dio_size drivers/block/loop.c:464 [inline] loop_assign_backing_file+0x1d8/0x390 drivers/block/loop.c:517 loop_change_fd drivers/block/loop.c:597 [inline] lo_ioctl+0x1234/0x177c drivers/block/loop.c:1546 blkdev_ioctl+0x62c/0xadc block/ioctl.c:791 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:583 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 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.1.80/7108: #0: ffff0000cba5e448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline] #0: ffff0000cba5e448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_change_fd drivers/block/loop.c:562 [inline] #0: ffff0000cba5e448 (&lo->lo_mutex){+.+.}-{4:4}, at: lo_ioctl+0xd20/0x177c drivers/block/loop.c:1546 #1: ffff0000cb935f60 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:954 [inline] #1: ffff0000cb935f60 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] #1: ffff0000cb935f60 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: lo_ioctl+0x11e0/0x177c drivers/block/loop.c:1546 #2: ffff0000cb935f98 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:954 [inline] #2: ffff0000cb935f98 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: loop_change_fd drivers/block/loop.c:595 [inline] #2: ffff0000cb935f98 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: lo_ioctl+0x11e0/0x177c drivers/block/loop.c:1546 stack backtrace: CPU: 1 UID: 0 PID: 7108 Comm: syz.1.80 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (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:2043 check_noncircular+0x154/0x174 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+0x1774/0x30a4 kernel/locking/lockdep.c:5237 lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868 down_read+0x58/0x308 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0xa0/0x410 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x254/0x38c fs/stat.c:213 vfs_getattr+0x60/0x84 fs/stat.c:262 loop_query_min_dio_size drivers/block/loop.c:464 [inline] loop_assign_backing_file+0x1d8/0x390 drivers/block/loop.c:517 loop_change_fd drivers/block/loop.c:597 [inline] lo_ioctl+0x1234/0x177c drivers/block/loop.c:1546 blkdev_ioctl+0x62c/0xadc block/ioctl.c:791 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:583 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xe8/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x26c arch/arm64/kernel/entry-common.c:724 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596