======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.3.4178/20720 is trying to acquire lock:
ffff888076f29d38 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609

but task is already holding lock:
ffff88801c2cc980 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x26d/0x960 fs/kernfs/dir.c:1982

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x96/0x200 kernel/locking/rwsem.c:1631
       kernfs_add_one+0x41/0x6f0 fs/kernfs/dir.c:825
       kernfs_create_dir_ns+0x1a1/0x230 fs/kernfs/dir.c:1130
       sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x622/0xcd0 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+0x118/0x2f0 fs/btrfs/sysfs.c:2604
       btrfs_quota_enable+0x274/0x1e20 fs/btrfs/qgroup.c:1032
       btrfs_ioctl_quota_ctl+0x186/0x1f0 fs/btrfs/ioctl.c:3566
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&fs_info->qgroup_ioctl_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       btrfs_quota_enable+0x2b1/0x1e20 fs/btrfs/qgroup.c:1061
       btrfs_ioctl_quota_ctl+0x186/0x1f0 fs/btrfs/ioctl.c:3566
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x18a/0xd40 fs/btrfs/transaction.c:324
       start_transaction+0x6ed/0x17d0 fs/btrfs/transaction.c:718
       btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6446
       touch_atime+0x2f8/0x670 fs/inode.c:2326
       file_accessed include/linux/fs.h:2278 [inline]
       filemap_read+0xffc/0x11e0 mm/filemap.c:2896
       __kernel_read+0x4ca/0x960 fs/read_write.c:532
       integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
       ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
       ima_calc_file_hash+0x451/0x890 security/integrity/ima/ima_crypto.c:280
       ima_collect_measurement+0x51b/0xa00 security/integrity/ima/ima_api.c:300
       process_measurement+0x1272/0x1c10 security/integrity/ima/ima_main.c:425
       ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
       security_file_post_open+0xb3/0x260 security/security.c:2755
       do_open fs/namei.c:4839 [inline]
       path_openat+0x1485/0x1d60 fs/namei.c:5000
       do_file_open+0x23e/0x4a0 fs/namei.c:5029
       do_sys_openat2+0x115/0x200 fs/open.c:1417
       do_sys_open fs/open.c:1423 [inline]
       __do_sys_openat fs/open.c:1439 [inline]
       __se_sys_openat fs/open.c:1434 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1434
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
       __lock_release kernel/locking/lockdep.c:5592 [inline]
       lock_release+0x199/0x3c0 kernel/locking/lockdep.c:5907
       percpu_up_read include/linux/percpu-rwsem.h:114 [inline]
       __sb_end_write include/linux/fs/super.h:14 [inline]
       sb_end_intwrite+0x26/0x190 include/linux/fs/super.h:101
       __btrfs_end_transaction+0x23f/0x640 fs/btrfs/transaction.c:1095
       btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6460
       touch_atime+0x2f8/0x670 fs/inode.c:2326
       file_accessed include/linux/fs.h:2278 [inline]
       btrfs_file_mmap_prepare+0x172/0x1f0 fs/btrfs/file.c:2003
       vfs_mmap_prepare include/linux/fs.h:2070 [inline]
       call_mmap_prepare mm/vma.c:2734 [inline]
       __mmap_region mm/vma.c:2820 [inline]
       mmap_region+0xe5a/0x2230 mm/vma.c:2921
       do_mmap+0xe0a/0x1300 mm/mmap.c:573
       vm_mmap_pgoff+0x272/0x4e0 mm/util.c:581
       ksys_mmap_pgoff+0x4dc/0x760 mm/mmap.c:619
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&mm->mmap_lock){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3181 [inline]
       check_prevs_add kernel/locking/lockdep.c:3300 [inline]
       validate_chain kernel/locking/lockdep.c:3924 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5253
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886
       down_read_killable+0x50/0x3b0 kernel/locking/rwsem.c:1599
       mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609
       get_mmap_lock_carefully mm/mmap_lock.c:450 [inline]
       lock_mm_and_find_vma+0x2d6/0x340 mm/mmap_lock.c:501
       do_user_addr_fault+0x343/0x1340 arch/x86/mm/fault.c:1366
       handle_page_fault arch/x86/mm/fault.c:1483 [inline]
       exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
       filldir+0x2bd/0x630 fs/readdir.c:-1
       dir_emit include/linux/fs.h:3608 [inline]
       kernfs_fop_readdir+0x580/0x960 fs/kernfs/dir.c:1999
       iterate_dir+0x2e2/0x4d0 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:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       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 ***

locks held by syz.3.4178/20720: 3, last CPU#1:
 #0: ffff88807e9d7b30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 fs/file.c:1259
 #1: ffff88807a45a280 (&type->i_mutex_dir_key#4){++++}-{4:4}, at: iterate_dir+0x209/0x4d0 fs/readdir.c:103
 #2: ffff88801c2cc980 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_fop_readdir+0x26d/0x960 fs/kernfs/dir.c:1982

stack backtrace:
CPU: 1 UID: 0 PID: 20720 Comm: syz.3.4178 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2059
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2191
 check_prev_add kernel/locking/lockdep.c:3181 [inline]
 check_prevs_add kernel/locking/lockdep.c:3300 [inline]
 validate_chain kernel/locking/lockdep.c:3924 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5253
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886
 down_read_killable+0x50/0x3b0 kernel/locking/rwsem.c:1599
 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:609
 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline]
 lock_mm_and_find_vma+0x2d6/0x340 mm/mmap_lock.c:501
 do_user_addr_fault+0x343/0x1340 arch/x86/mm/fault.c:1366
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0010:filldir+0x2bd/0x630 fs/readdir.c:290
Code: 89 b4 76 ff 0f 01 cb 48 8b 44 24 20 49 89 47 08 48 bd 00 00 00 00 00 fc ff df 48 8b 44 24 40 48 89 03 8b 4c 24 04 48 8d 43 10 <66> 89 08 8b 54 24 14 80 e2 0f 89 c9 48 8d 04 0b 48 ff c8 88 10 48
RSP: 0018:ffffc90006fcfc50 EFLAGS: 00050297
RAX: 0000200000002000 RBX: 0000200000001ff0 RCX: 0000000000000020
RDX: 0000000000000002 RSI: 0000000000000006 RDI: 0000000000000007
RBP: dffffc0000000000 R08: ffff888067beddc7 R09: 1ffff1100cf7dbb8
R10: dffffc0000000000 R11: ffffed100cf7dbb9 R12: ffffffff8c0be200
R13: 0000000000000006 R14: 0000000000000006 R15: 0000200000001fd8
 dir_emit include/linux/fs.h:3608 [inline]
 kernfs_fop_readdir+0x580/0x960 fs/kernfs/dir.c:1999
 iterate_dir+0x2e2/0x4d0 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:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc179f9e0d9
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:00007fc17aeda028 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007fc17a225fa0 RCX: 00007fc179f9e0d9
RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000005
RBP: 00007fc17a035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc17a226038 R14: 00007fc17a225fa0 R15: 00007ffd858fac98
 </TASK>
----------------
Code disassembly (best guess):
   0:	89 b4 76 ff 0f 01 cb 	mov    %esi,-0x34fef001(%rsi,%rsi,2)
   7:	48 8b 44 24 20       	mov    0x20(%rsp),%rax
   c:	49 89 47 08          	mov    %rax,0x8(%r15)
  10:	48 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%rbp
  17:	fc ff df
  1a:	48 8b 44 24 40       	mov    0x40(%rsp),%rax
  1f:	48 89 03             	mov    %rax,(%rbx)
  22:	8b 4c 24 04          	mov    0x4(%rsp),%ecx
  26:	48 8d 43 10          	lea    0x10(%rbx),%rax
* 2a:	66 89 08             	mov    %cx,(%rax) <-- trapping instruction
  2d:	8b 54 24 14          	mov    0x14(%rsp),%edx
  31:	80 e2 0f             	and    $0xf,%dl
  34:	89 c9                	mov    %ecx,%ecx
  36:	48 8d 04 0b          	lea    (%rbx,%rcx,1),%rax
  3a:	48 ff c8             	dec    %rax
  3d:	88 10                	mov    %dl,(%rax)
  3f:	48                   	rex.W