====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.1127/14292 is trying to acquire lock: ffff88803dbe1db0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 but task is already holding lock: ffff88801a085238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x269/0x950 fs/kernfs/dir.c:1983 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&root->kernfs_rwsem){++++}-{4:4}: down_write+0x3a/0x50 kernel/locking/rwsem.c:1625 kernfs_add_one+0x41/0x5c0 fs/kernfs/dir.c:826 kernfs_create_dir_ns+0xde/0x130 fs/kernfs/dir.c:1131 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59 create_dir lib/kobject.c:73 [inline] kobject_add_internal+0x631/0xd10 lib/kobject.c:240 kobject_add_varg lib/kobject.c:374 [inline] kobject_init_and_add+0x12b/0x1a0 lib/kobject.c:457 btrfs_sysfs_add_qgroups+0x116/0x2e0 fs/btrfs/sysfs.c:2604 btrfs_quota_enable+0x282/0x2850 fs/btrfs/qgroup.c:1034 btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3541 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:534 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:553 btrfs_quota_enable+0x2c6/0x2850 fs/btrfs/qgroup.c:1063 btrfs_ioctl_quota_ctl+0x186/0x1c0 fs/btrfs/ioctl.c:3541 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x192/0xd50 fs/btrfs/transaction.c:324 start_transaction+0xbe9/0x1820 fs/btrfs/transaction.c:719 create_subvol+0x493/0x1a80 fs/btrfs/ioctl.c:560 btrfs_mksubvol+0x474/0x10a0 fs/btrfs/ioctl.c:865 __btrfs_ioctl_snap_create+0x2c3/0x750 fs/btrfs/ioctl.c:1138 btrfs_ioctl_snap_create+0x134/0x180 fs/btrfs/ioctl.c:1195 btrfs_ioctl+0x6e5/0xd10 fs/btrfs/ioctl.c:-1 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x199/0x3c0 kernel/locking/lockdep.c:5889 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs/super.h:14 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs/super.h:101 __btrfs_end_transaction+0x248/0x650 fs/btrfs/transaction.c:1096 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6457 touch_atime+0x2f8/0x6b0 fs/inode.c:2271 file_accessed include/linux/fs.h:2264 [inline] btrfs_file_mmap_prepare+0x189/0x200 fs/btrfs/file.c:2051 vfs_mmap_prepare include/linux/fs.h:2076 [inline] call_mmap_prepare mm/vma.c:2672 [inline] __mmap_region mm/vma.c:2755 [inline] mmap_region+0xeb9/0x2280 mm/vma.c:2857 do_mmap+0xc2f/0x10c0 mm/mmap.c:560 vm_mmap_pgoff+0x2cc/0x4f0 mm/util.c:581 ksys_mmap_pgoff+0x4e8/0x720 mm/mmap.c:606 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&mm->mmap_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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1593 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline] lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501 do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 filldir+0x2b3/0x650 fs/readdir.c:289 dir_emit include/linux/fs.h:3578 [inline] kernfs_fop_readdir+0x578/0x950 fs/kernfs/dir.c:2000 iterate_dir+0x3a5/0x580 fs/readdir.c:110 __do_sys_getdents fs/readdir.c:319 [inline] __se_sys_getdents+0xf1/0x270 fs/readdir.c:304 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 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: &mm->mmap_lock --> &fs_info->qgroup_ioctl_lock --> &root->kernfs_rwsem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&root->kernfs_rwsem); lock(&fs_info->qgroup_ioctl_lock); lock(&root->kernfs_rwsem); rlock(&mm->mmap_lock); *** DEADLOCK *** 3 locks held by syz.0.1127/14292: #0: ffff8880602a1128 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1261 #1: ffff88803dde3cf0 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:103 #2: ffff88801a085238 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x269/0x950 fs/kernfs/dir.c:1983 stack backtrace: CPU: 1 UID: 0 PID: 14292 Comm: syz.0.1127 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 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+0x106/0x350 kernel/locking/lockdep.c:5868 down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1593 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline] lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501 do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0010:filldir+0x2b3/0x650 fs/readdir.c:290 Code: 00 48 39 c8 48 0f 47 c1 0f 01 cb 48 8b 4c 24 30 48 89 48 08 48 bd 00 00 00 00 00 fc ff df 48 8b 44 24 28 48 89 02 8b 44 24 04 <66> 89 42 10 41 80 e7 0f 89 c0 44 88 7c 02 ff 48 89 44 24 28 42 c6 RSP: 0018:ffffc9000e1ffc38 EFLAGS: 00050287 RAX: 0000000000000020 RBX: ffffc9000e1ffe38 RCX: 0000000006f24808 RDX: 0000200000001ff8 RSI: 000000000000030d RDI: 000000000000030e RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000000 R10: dffffc0000000000 R11: ffffed1005c903d9 R12: ffff888030ef8f00 R13: 000000000000000c R14: 000000000000000c R15: 0000000000000008 dir_emit include/linux/fs.h:3578 [inline] kernfs_fop_readdir+0x578/0x950 fs/kernfs/dir.c:2000 iterate_dir+0x3a5/0x580 fs/readdir.c:110 __do_sys_getdents fs/readdir.c:319 [inline] __se_sys_getdents+0xf1/0x270 fs/readdir.c:304 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa65f32ce59 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa65d586028 EFLAGS: 00000246 ORIG_RAX: 000000000000004e RAX: ffffffffffffffda RBX: 00007fa65f5a5fa0 RCX: 00007fa65f32ce59 RDX: 0000000000001000 RSI: 0000200000001f80 RDI: 0000000000000003 RBP: 00007fa65f3c2d6f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa65f5a6038 R14: 00007fa65f5a5fa0 R15: 00007fffa1350768 ---------------- Code disassembly (best guess): 0: 00 48 39 add %cl,0x39(%rax) 3: c8 48 0f 47 enter $0xf48,$0x47 7: c1 0f 01 rorl $0x1,(%rdi) a: cb lret b: 48 8b 4c 24 30 mov 0x30(%rsp),%rcx 10: 48 89 48 08 mov %rcx,0x8(%rax) 14: 48 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%rbp 1b: fc ff df 1e: 48 8b 44 24 28 mov 0x28(%rsp),%rax 23: 48 89 02 mov %rax,(%rdx) 26: 8b 44 24 04 mov 0x4(%rsp),%eax * 2a: 66 89 42 10 mov %ax,0x10(%rdx) <-- trapping instruction 2e: 41 80 e7 0f and $0xf,%r15b 32: 89 c0 mov %eax,%eax 34: 44 88 7c 02 ff mov %r15b,-0x1(%rdx,%rax,1) 39: 48 89 44 24 28 mov %rax,0x28(%rsp) 3e: 42 rex.X 3f: c6 .byte 0xc6