====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.6.273/8461 is trying to acquire lock: ffff0000db885978 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}, at: btrfs_quota_enable+0x250/0x2208 fs/btrfs/qgroup.c:1051 but task is already holding lock: ffff0000db886538 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x164/0xb5c fs/btrfs/transaction.c:320 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x190/0xb5c fs/btrfs/transaction.c:321 start_transaction+0x778/0x155c fs/btrfs/transaction.c:705 btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:816 btrfs_rebuild_free_space_tree+0xac/0x75c fs/btrfs/free-space-tree.c:1339 btrfs_start_pre_rw_mount+0xed8/0x1728 fs/btrfs/disk-io.c:3075 open_ctree+0x2324/0x32c4 fs/btrfs/disk-io.c:3617 btrfs_fill_super fs/btrfs/super.c:977 [inline] btrfs_get_tree_super fs/btrfs/super.c:1940 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2077 [inline] btrfs_get_tree+0xd5c/0x159c fs/btrfs/super.c:2111 vfs_get_tree+0x90/0x28c fs/super.c:1815 do_new_mount+0x278/0x7f4 fs/namespace.c:3808 path_mount+0x5b4/0xde0 fs/namespace.c:4123 do_mount fs/namespace.c:4136 [inline] __do_sys_mount fs/namespace.c:4347 [inline] __se_sys_mount fs/namespace.c:4324 [inline] __arm64_sys_mount+0x3e8/0x468 fs/namespace.c:4324 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #3 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x198/0x39c kernel/locking/lockdep.c:5889 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs.h:1793 [inline] sb_end_intwrite+0x3c/0x348 include/linux/fs.h:1910 __btrfs_end_transaction+0x1f4/0x5f4 fs/btrfs/transaction.c:1076 btrfs_end_transaction+0x24/0x34 fs/btrfs/transaction.c:1110 btrfs_dirty_inode+0x140/0x190 fs/btrfs/inode.c:6249 btrfs_update_time+0xa0/0xd0 fs/btrfs/inode.c:6269 inode_update_time fs/inode.c:2075 [inline] touch_atime+0x2e4/0x818 fs/inode.c:2148 file_accessed include/linux/fs.h:2663 [inline] btrfs_file_mmap_prepare+0xc4/0x130 fs/btrfs/file.c:2050 vfs_mmap_prepare include/linux/fs.h:2294 [inline] call_mmap_prepare mm/vma.c:2585 [inline] __mmap_region mm/vma.c:2653 [inline] mmap_region+0x934/0x1d20 mm/vma.c:2739 do_mmap+0x968/0xfac mm/mmap.c:558 vm_mmap_pgoff+0x2d8/0x45c mm/util.c:580 ksys_mmap_pgoff+0x394/0x5b8 mm/mmap.c:604 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline] __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline] __arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #2 (&mm->mmap_lock){++++}-{4:4}: down_read_killable+0x60/0x32c kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x28/0x8c include/linux/mmap_lock.h:462 get_mmap_lock_carefully mm/mmap_lock.c:286 [inline] lock_mm_and_find_vma+0x2a4/0x2d8 mm/mmap_lock.c:337 do_page_fault+0x50c/0x13cc arch/arm64/mm/fault.c:674 do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:789 do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:929 el1_abort+0x40/0x64 arch/arm64/kernel/entry-common.c:325 el1h_64_sync_handler+0x50/0xfc arch/arm64/kernel/entry-common.c:459 el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:591 __uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:169 [inline] filldir64+0x2dc/0x6bc fs/readdir.c:378 dir_emit include/linux/fs.h:3958 [inline] kernfs_fop_readdir+0x498/0x79c fs/kernfs/dir.c:1910 iterate_dir+0x2dc/0x478 fs/readdir.c:108 __do_sys_getdents64 fs/readdir.c:410 [inline] __se_sys_getdents64 fs/readdir.c:396 [inline] __arm64_sys_getdents64+0x110/0x2fc fs/readdir.c:396 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #1 (&root->kernfs_rwsem){++++}-{4:4}: down_write+0x50/0xc0 kernel/locking/rwsem.c:1590 kernfs_add_one+0x48/0x60c fs/kernfs/dir.c:791 kernfs_create_dir_ns+0xd4/0x12c fs/kernfs/dir.c:1093 sysfs_create_dir_ns+0x114/0x24c fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x5a8/0xb20 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_init_and_add+0x118/0x17c lib/kobject.c:457 btrfs_sysfs_add_qgroups+0x110/0x268 fs/btrfs/sysfs.c:2641 btrfs_quota_enable+0x214/0x2208 fs/btrfs/qgroup.c:1022 btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3667 btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5318 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #0 (&fs_info->qgroup_ioctl_lock){+.+.}-{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+0x14c/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598 __mutex_lock kernel/locking/mutex.c:760 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812 btrfs_quota_enable+0x250/0x2208 fs/btrfs/qgroup.c:1051 btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3667 btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5318 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 other info that might help us debug this: Chain exists of: &fs_info->qgroup_ioctl_lock --> btrfs_trans_num_writers --> btrfs_trans_num_extwriters Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(btrfs_trans_num_extwriters); lock(btrfs_trans_num_writers); lock(btrfs_trans_num_extwriters); lock(&fs_info->qgroup_ioctl_lock); *** DEADLOCK *** 5 locks held by syz.6.273/8461: #0: ffff0000dcb0a428 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x64/0x1e8 fs/namespace.c:601 #1: ffff0000db884c40 (&fs_info->subvol_sem){+.+.}-{4:4}, at: btrfs_ioctl_quota_ctl+0x16c/0x1bc fs/btrfs/ioctl.c:3666 #2: ffff0000dcb0a618 (sb_internal#2){.+.+}-{0:0}, at: btrfs_start_transaction+0x34/0x44 fs/btrfs/transaction.c:816 #3: ffff0000db886510 (btrfs_trans_num_writers){++++}-{0:0}, at: join_transaction+0x134/0xb5c fs/btrfs/transaction.c:317 #4: ffff0000db886538 (btrfs_trans_num_extwriters){++++}-{0:0}, at: join_transaction+0x164/0xb5c fs/btrfs/transaction.c:320 stack backtrace: CPU: 0 UID: 0 PID: 8461 Comm: syz.6.273 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025 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+0x14c/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598 __mutex_lock kernel/locking/mutex.c:760 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812 btrfs_quota_enable+0x250/0x2208 fs/btrfs/qgroup.c:1051 btrfs_ioctl_quota_ctl+0x178/0x1bc fs/btrfs/ioctl.c:3667 btrfs_ioctl+0x86c/0xc3c fs/btrfs/ioctl.c:5318 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596