syzbot

======================================================
WARNING: possible circular locking dependency detected
6.16.0-syzkaller-12016-gbec077162bd0 #0 Not tainted
------------------------------------------------------
syz.5.3818/22237 is trying to acquire lock:
ffff88806464a618 (sb_internal#2){.+.+}-{0:0}, at: btrfs_dirty_inode+0xc8/0x200 fs/btrfs/inode.c:6216

but task is already holding lock:
ffff888028428ca0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:415 [inline]
ffff888028428ca0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x1f5/0x470 mm/util.c:578

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&mm->mmap_lock){++++}-{4:4}:
       down_read_killable+0x9e/0x4b0 kernel/locking/rwsem.c:1560
       mmap_read_lock_killable include/linux/mmap_lock.h:462 [inline]
       get_mmap_lock_carefully mm/mmap_lock.c:286 [inline]
       lock_mm_and_find_vma+0x3e7/0x6e0 mm/mmap_lock.c:337
       do_user_addr_fault+0x2ac/0x1370 arch/x86/mm/fault.c:1359
       handle_page_fault arch/x86/mm/fault.c:1476 [inline]
       exc_page_fault+0x5c/0xb0 arch/x86/mm/fault.c:1532
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
       filldir64+0x211/0x600 fs/readdir.c:381
       dir_emit include/linux/fs.h:3958 [inline]
       kernfs_fop_readdir+0x3d8/0x930 fs/kernfs/dir.c:1910
       iterate_dir+0x296/0xaf0 fs/readdir.c:108
       __do_sys_getdents64 fs/readdir.c:410 [inline]
       __se_sys_getdents64 fs/readdir.c:396 [inline]
       __x64_sys_getdents64+0x13c/0x2c0 fs/readdir.c:396
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x92/0x200 kernel/locking/rwsem.c:1590
       kernfs_add_one+0x38/0x840 fs/kernfs/dir.c:791
       kernfs_create_dir_ns+0xfc/0x1a0 fs/kernfs/dir.c:1093
       sysfs_create_dir_ns+0x13a/0x2b0 fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x2c4/0x9b0 lib/kobject.c:240
       kobject_add_varg lib/kobject.c:374 [inline]
       kobject_init_and_add+0x11b/0x190 lib/kobject.c:457
       btrfs_sysfs_add_qgroups+0x113/0x250 fs/btrfs/sysfs.c:2641
       btrfs_quota_enable+0x32a/0x2a60 fs/btrfs/qgroup.c:1022
       btrfs_ioctl_quota_ctl fs/btrfs/ioctl.c:3667 [inline]
       btrfs_ioctl+0x45a4/0x5590 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]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 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/mutex.c:598 [inline]
       __mutex_lock+0x193/0x10b0 kernel/locking/mutex.c:760
       btrfs_quota_enable+0x36c/0x2a60 fs/btrfs/qgroup.c:1051
       btrfs_ioctl_quota_ctl fs/btrfs/ioctl.c:3667 [inline]
       btrfs_ioctl+0x45a4/0x5590 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]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x165/0x1020 fs/btrfs/transaction.c:321
       start_transaction+0x430/0x1b00 fs/btrfs/transaction.c:705
       btrfs_create_common+0x189/0x260 fs/btrfs/inode.c:6738
       btrfs_create+0x114/0x160 fs/btrfs/inode.c:6784
       lookup_open.isra.0+0x11d3/0x1580 fs/namei.c:3708
       open_last_lookups fs/namei.c:3807 [inline]
       path_openat+0x893/0x2cb0 fs/namei.c:4043
       do_filp_open+0x20b/0x470 fs/namei.c:4073
       do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
       do_sys_open fs/open.c:1450 [inline]
       __do_sys_open fs/open.c:1458 [inline]
       __se_sys_open fs/open.c:1454 [inline]
       __x64_sys_open+0x153/0x1e0 fs/open.c:1454
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
       join_transaction+0x149/0x1020 fs/btrfs/transaction.c:320
       start_transaction+0x430/0x1b00 fs/btrfs/transaction.c:705
       btrfs_create_common+0x189/0x260 fs/btrfs/inode.c:6738
       btrfs_create+0x114/0x160 fs/btrfs/inode.c:6784
       lookup_open.isra.0+0x11d3/0x1580 fs/namei.c:3708
       open_last_lookups fs/namei.c:3807 [inline]
       path_openat+0x893/0x2cb0 fs/namei.c:4043
       do_filp_open+0x20b/0x470 fs/namei.c:4073
       do_sys_openat2+0x11b/0x1d0 fs/open.c:1435
       do_sys_open fs/open.c:1450 [inline]
       __do_sys_open fs/open.c:1458 [inline]
       __se_sys_open fs/open.c:1454 [inline]
       __x64_sys_open+0x153/0x1e0 fs/open.c:1454
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_internal#2){.+.+}-{0:0}:
       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+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
       __sb_start_write include/linux/fs.h:1798 [inline]
       sb_start_intwrite include/linux/fs.h:1981 [inline]
       start_transaction+0xbe3/0x1b00 fs/btrfs/transaction.c:699
       btrfs_dirty_inode+0xc8/0x200 fs/btrfs/inode.c:6216
       btrfs_update_time fs/btrfs/inode.c:6250 [inline]
       btrfs_update_time+0xb2/0xf0 fs/btrfs/inode.c:6241
       inode_update_time fs/inode.c:2075 [inline]
       touch_atime+0x352/0x5d0 fs/inode.c:2148
       file_accessed include/linux/fs.h:2663 [inline]
       btrfs_file_mmap_prepare+0x132/0x180 fs/btrfs/file.c:2050
       vfs_mmap_prepare include/linux/fs.h:2294 [inline]
       call_mmap_prepare mm/vma.c:2585 [inline]
       __mmap_region+0xee5/0x27b0 mm/vma.c:2653
       mmap_region+0x32b/0x3f0 mm/vma.c:2739
       do_mmap+0xa3e/0x1210 mm/mmap.c:558
       vm_mmap_pgoff+0x29e/0x470 mm/util.c:580
       ksys_mmap_pgoff+0x32c/0x5c0 mm/mmap.c:604
       __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
       __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
       __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 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:
  sb_internal#2 --> &root->kernfs_rwsem --> &mm->mmap_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_lock);
                               lock(&root->kernfs_rwsem);
                               lock(&mm->mmap_lock);
  rlock(sb_internal#2);

 *** DEADLOCK ***

2 locks held by syz.5.3818/22237:
 #0: ffff888028428ca0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:415 [inline]
 #0: ffff888028428ca0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x1f5/0x470 mm/util.c:578
 #1: ffff88806464a428 (sb_writers#14){.+.+}-{0:0}, at: file_accessed include/linux/fs.h:2663 [inline]
 #1: ffff88806464a428 (sb_writers#14){.+.+}-{0:0}, at: btrfs_file_mmap_prepare+0x132/0x180 fs/btrfs/file.c:2050

stack backtrace:
CPU: 1 UID: 0 PID: 22237 Comm: syz.5.3818 Not tainted 6.16.0-syzkaller-12016-gbec077162bd0 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043
 check_noncircular+0x14c/0x170 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+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs.h:1798 [inline]
 sb_start_intwrite include/linux/fs.h:1981 [inline]
 start_transaction+0xbe3/0x1b00 fs/btrfs/transaction.c:699
 btrfs_dirty_inode+0xc8/0x200 fs/btrfs/inode.c:6216
 btrfs_update_time fs/btrfs/inode.c:6250 [inline]
 btrfs_update_time+0xb2/0xf0 fs/btrfs/inode.c:6241
 inode_update_time fs/inode.c:2075 [inline]
 touch_atime+0x352/0x5d0 fs/inode.c:2148
 file_accessed include/linux/fs.h:2663 [inline]
 btrfs_file_mmap_prepare+0x132/0x180 fs/btrfs/file.c:2050
 vfs_mmap_prepare include/linux/fs.h:2294 [inline]
 call_mmap_prepare mm/vma.c:2585 [inline]
 __mmap_region+0xee5/0x27b0 mm/vma.c:2653
 mmap_region+0x32b/0x3f0 mm/vma.c:2739
 do_mmap+0xa3e/0x1210 mm/mmap.c:558
 vm_mmap_pgoff+0x29e/0x470 mm/util.c:580
 ksys_mmap_pgoff+0x32c/0x5c0 mm/mmap.c:604
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
 __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f76f378ebe9
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:00007f76f45f0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f76f39b6180 RCX: 00007f76f378ebe9
RDX: 000000000000000a RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f76f3811e19 R08: 0000000000000006 R09: 0000000000000000
R10: 0000000000028011 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f76f39b6218 R14: 00007f76f39b6180 R15: 00007fffbdf57658
 </TASK>