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possible deadlock in ext4_move_extents (4)

Status: upstream: reported on 2025/02/01 20:02
Reported-by: syzbot+64797b288ec15d559468@syzkaller.appspotmail.com
First crash: 177d, last: 9d09h
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in ext4_move_extents 4 2 725d 814d 0/3 auto-obsoleted due to no activity on 2023/11/11 09:48
linux-6.1 possible deadlock in ext4_move_extents (3) 4 16 5d15h 277d 0/3 upstream: reported on 2024/10/24 22:08
upstream possible deadlock in ext4_move_extents ext4 4 133 826d 996d 0/29 auto-obsoleted due to no activity on 2023/08/22 15:17
linux-6.1 possible deadlock in ext4_move_extents (2) 4 6 413d 592d 0/3 auto-obsoleted due to no activity on 2024/09/18 11:30
linux-5.15 possible deadlock in ext4_move_extents 4 3 751d 826d 0/3 auto-obsoleted due to no activity on 2023/10/16 22:21
linux-5.15 possible deadlock in ext4_move_extents (2) 4 2 553d 623d 0/3 auto-obsoleted due to no activity on 2024/05/01 17:40
linux-5.15 possible deadlock in ext4_move_extents (3) 4 5 297d 426d 0/3 auto-obsoleted due to no activity on 2025/01/12 16:14

Sample crash report:
EXT4-fs (loop7): mounted filesystem without journal. Opts: ,errors=continue. Quota mode: writeback.
ext4 filesystem being mounted at /148/bus supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
5.15.189-syzkaller #0 Not tainted
------------------------------------------------------
syz.7.2930/19018 is trying to acquire lock:
ffff8880614ce628
 (&ei->i_data_sem
/1
){+.+.}-{3:3}
, at: ext4_move_extents+0x31e/0xbd0 fs/ext4/move_extent.c:609

but task is already holding lock:
ffff888061467020
 (&ei->i_data_sem
/2){++++}-{3:3}
, at: ext4_double_down_write_data_sem+0x28/0x40 fs/ext4/move_extent.c:-1

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3
 (
&ei->i_data_sem
/2
){++++}-{3:3}
:
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       ext4_map_blocks+0x32f/0x1b30 fs/ext4/inode.c:598
       ext4_getblk+0x16d/0x630 fs/ext4/inode.c:870
       ext4_bread+0x26/0x180 fs/ext4/inode.c:923
       ext4_quota_write+0x230/0x570 fs/ext4/super.c:6594
       write_blk fs/quota/quota_tree.c:64 [inline]
       get_free_dqblk+0x387/0x7d0 fs/quota/quota_tree.c:125
       do_insert_tree+0x214/0x1970 fs/quota/quota_tree.c:335
       do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
       do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
       do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
       dq_insert_tree fs/quota/quota_tree.c:392 [inline]
       qtree_write_dquot+0x361/0x4b0 fs/quota/quota_tree.c:411
       v2_write_dquot+0x108/0x190 fs/quota/quota_v2.c:358
       dquot_acquire+0x2d5/0x520 fs/quota/dquot.c:472
       ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6203
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       dquot_transfer+0x1e1/0x480 fs/quota/dquot.c:2146
       ext4_setattr+0x72a/0x19e0 fs/ext4/inode.c:5452
       notify_change+0xbcd/0xee0 fs/attr.c:505
       chown_common+0x483/0x610 fs/open.c:680
       do_fchownat+0x164/0x270 fs/open.c:711
       __do_sys_chown fs/open.c:731 [inline]
       __se_sys_chown fs/open.c:729 [inline]
       __x64_sys_chown+0x7e/0x90 fs/open.c:729
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       v2_read_dquot+0x4a/0x110 fs/quota/quota_v2.c:332
       dquot_acquire+0x152/0x520 fs/quota/dquot.c:463
       ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6203
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       __dquot_initialize+0x3b6/0xcb0 fs/quota/dquot.c:1517
       ext4_mkdir+0x16c/0xc50 fs/ext4/namei.c:3059
       vfs_mkdir+0x387/0x570 fs/namei.c:4065
       do_mkdirat+0x1d7/0x5a0 fs/namei.c:4090
       __do_sys_mkdirat fs/namei.c:4105 [inline]
       __se_sys_mkdirat fs/namei.c:4103 [inline]
       __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&dquot->dq_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       dquot_commit+0x5a/0x410 fs/quota/dquot.c:507
       ext4_write_dquot+0x1f0/0x360 fs/ext4/super.c:6183
       mark_dquot_dirty fs/quota/dquot.c:372 [inline]
       mark_all_dquot_dirty+0xf9/0x400 fs/quota/dquot.c:412
       __dquot_alloc_space+0x5d0/0xe20 fs/quota/dquot.c:1752
       dquot_alloc_space_nodirty include/linux/quotaops.h:297 [inline]
       dquot_alloc_space include/linux/quotaops.h:310 [inline]
       dquot_alloc_block include/linux/quotaops.h:334 [inline]
       ext4_mb_new_blocks+0xf68/0x4940 fs/ext4/mballoc.c:5739
       ext4_new_meta_blocks+0x151/0x3a0 fs/ext4/balloc.c:738
       ext4_ext_grow_indepth fs/ext4/extents.c:1325 [inline]
       ext4_ext_create_new_leaf fs/ext4/extents.c:1431 [inline]
       ext4_ext_insert_extent+0x1075/0x47e0 fs/ext4/extents.c:2103
       ext4_split_extent_at+0x788/0xeb0 fs/ext4/extents.c:3235
       ext4_force_split_extent_at fs/ext4/extents.c:319 [inline]
       ext4_swap_extents+0xd99/0x1c50 fs/ext4/extents.c:5756
       move_extent_per_page+0x17c5/0x2e10 fs/ext4/move_extent.c:359
       ext4_move_extents+0x8b4/0xbd0 fs/ext4/move_extent.c:673
       __ext4_ioctl fs/ext4/ioctl.c:990 [inline]
       ext4_ioctl+0x2ce3/0x3590 fs/ext4/ioctl.c:1282
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&ei->i_data_sem/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       down_write_nested+0x3b/0x60 kernel/locking/rwsem.c:1667
       ext4_move_extents+0x31e/0xbd0 fs/ext4/move_extent.c:609
       __ext4_ioctl fs/ext4/ioctl.c:990 [inline]
       ext4_ioctl+0x2ce3/0x3590 fs/ext4/ioctl.c:1282
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  &ei->i_data_sem/1 --> &s->s_dquot.dqio_sem --> &ei->i_data_sem/2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->i_data_sem/2);
                               lock(&s->s_dquot.dqio_sem);
                               lock(&ei->i_data_sem/2);
  lock(&ei->i_data_sem/1);

 *** DEADLOCK ***

4 locks held by syz.7.2930/19018:
 #0: ffff888029056460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:421
 #1: ffff888061467198 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff888061467198 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: lock_two_nondirectories+0xd5/0x150 fs/inode.c:1147
 #2: ffff8880614ce7a0 (&sb->s_type->i_mutex_key#9/4){+.+.}-{3:3}, at: ext4_move_extents+0x303/0xbd0 fs/ext4/move_extent.c:602
 #3: ffff888061467020 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40 fs/ext4/move_extent.c:-1

stack backtrace:
CPU: 1 PID: 19018 Comm: syz.7.2930 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 down_write_nested+0x3b/0x60 kernel/locking/rwsem.c:1667
 ext4_move_extents+0x31e/0xbd0 fs/ext4/move_extent.c:609
 __ext4_ioctl fs/ext4/ioctl.c:990 [inline]
 ext4_ioctl+0x2ce3/0x3590 fs/ext4/ioctl.c:1282
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff2989a89a9
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:00007ff296810038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff298bcffa0 RCX: 00007ff2989a89a9
RDX: 00002000000000c0 RSI: 00000000c028660f RDI: 0000000000000006
RBP: 00007ff298a2ad69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff298bcffa0 R15: 00007ffdc8260428
 </TASK>
EXT4-fs error (device loop7): ext4_lookup:1858: inode #12: comm syz.7.2930: iget: bad i_size value: 2533274857506816

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/19 18:05 linux-5.15.y c79648372d02 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/06/21 17:41 linux-5.15.y 1c700860e8bc d6cdfb8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/06/10 21:35 linux-5.15.y 1c700860e8bc 5d7e17ca .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/06/02 13:22 linux-5.15.y 98f47d0e9b8c b396b4bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/04/28 22:19 linux-5.15.y f7347f400572 aeb6ec69 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/02/24 00:00 linux-5.15.y c16c81c81336 d34966d1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/02/20 06:08 linux-5.15.y c16c81c81336 50668798 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/02/02 04:54 linux-5.15.y c16c81c81336 568559e4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
2025/02/01 20:01 linux-5.15.y c16c81c81336 aa47157c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_move_extents
* Struck through repros no longer work on HEAD.