possible deadlock in dqget (2)

Status: auto-obsoleted due to no activity on 2026/01/30 18:00
Reported-by: syzbot+48f6149796b9cd8dc4e4@syzkaller.appspotmail.com
First crash: 406d, last: 292d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 possible deadlock in dqget 4 28 154d 417d 0/2 auto-obsoleted due to no activity on 2026/06/18 06:57
linux-6.1 possible deadlock in dqget 4 1 560d 560d 0/3 auto-obsoleted due to no activity on 2025/05/07 22:20
upstream possible deadlock in dqget ocfs2 ext4 4 syz, C error 100357 225d 679d 29/29 fixed on 2026/01/07 12:29
linux-5.15 possible deadlock in dqget 4 1 199d 199d 0/3 auto-obsoleted due to no activity on 2026/05/03 22:00
upstream possible deadlock in dqget (2) ocfs2 prio:low 4 9 57d 199d 0/29 upstream: reported on 2026/01/24 00:53

Sample crash report:
loop3: detected capacity change from 0 to 512
EXT4-fs: Journaled quota options ignored when QUOTA feature is enabled
EXT4-fs (loop3): mounted filesystem without journal. Quota mode: writeback.
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.13039/1380 is trying to acquire lock:
ffff88804cc413e8 (&dquot->dq_lock){+.+.}-{3:3}, at: wait_on_dquot fs/quota/dquot.c:356 [inline]
ffff88804cc413e8 (&dquot->dq_lock){+.+.}-{3:3}, at: dqget+0x6f8/0xeb0 fs/quota/dquot.c:983

but task is already holding lock:
ffff8880253e32f0 (&ei->xattr_sem){++++}-{3:3}, at: ext4_setattr+0x92a/0x19f0 fs/ext4/inode.c:5501

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&ei->xattr_sem){++++}-{3:3}:
       down_read+0x42/0x2d0 kernel/locking/rwsem.c:1520
       ext4_setattr+0x92a/0x19f0 fs/ext4/inode.c:5501
       notify_change+0xc74/0xf40 fs/attr.c:499
       chown_common+0x486/0x620 fs/open.c:736
       do_fchownat+0x164/0x270 fs/open.c:767
       __do_sys_chown fs/open.c:787 [inline]
       __se_sys_chown fs/open.c:785 [inline]
       __x64_sys_chown+0x7e/0x90 fs/open.c:785
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #4 (jbd2_handle){++++}-{0:0}:
       start_this_handle+0x1f49/0x2150 fs/jbd2/transaction.c:463
       jbd2__journal_start+0x2b7/0x5a0 fs/jbd2/transaction.c:520
       jbd2_journal_start+0x26/0x30 fs/jbd2/transaction.c:559
       ocfs2_start_trans+0x372/0x6c0 fs/ocfs2/journal.c:376
       ocfs2_modify_bh+0xe5/0x460 fs/ocfs2/quota_local.c:101
       ocfs2_local_read_info+0x13b1/0x16e0 fs/ocfs2/quota_local.c:764
       dquot_load_quota_sb+0x756/0xac0 fs/quota/dquot.c:2470
       dquot_load_quota_inode+0x2d8/0x5d0 fs/quota/dquot.c:2507
       ocfs2_enable_quotas+0x1c3/0x440 fs/ocfs2/super.c:926
       ocfs2_fill_super+0x409f/0x4d00 fs/ocfs2/super.c:1139
       mount_bdev+0x287/0x3c0 fs/super.c:1443
       legacy_get_tree+0xe6/0x180 fs/fs_context.c:632
       vfs_get_tree+0x88/0x270 fs/super.c:1573
       do_new_mount+0x24a/0xa40 fs/namespace.c:3069
       do_mount fs/namespace.c:3412 [inline]
       __do_sys_mount fs/namespace.c:3620 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3597
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #3 (&journal->j_trans_barrier){.+.+}-{3:3}:
       down_read+0x42/0x2d0 kernel/locking/rwsem.c:1520
       ocfs2_start_trans+0x366/0x6c0 fs/ocfs2/journal.c:374
       ocfs2_modify_bh+0xe5/0x460 fs/ocfs2/quota_local.c:101
       ocfs2_local_read_info+0x13b1/0x16e0 fs/ocfs2/quota_local.c:764
       dquot_load_quota_sb+0x756/0xac0 fs/quota/dquot.c:2470
       dquot_load_quota_inode+0x2d8/0x5d0 fs/quota/dquot.c:2507
       ocfs2_enable_quotas+0x1c3/0x440 fs/ocfs2/super.c:926
       ocfs2_fill_super+0x409f/0x4d00 fs/ocfs2/super.c:1139
       mount_bdev+0x287/0x3c0 fs/super.c:1443
       legacy_get_tree+0xe6/0x180 fs/fs_context.c:632
       vfs_get_tree+0x88/0x270 fs/super.c:1573
       do_new_mount+0x24a/0xa40 fs/namespace.c:3069
       do_mount fs/namespace.c:3412 [inline]
       __do_sys_mount fs/namespace.c:3620 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3597
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (sb_internal#4){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1891 [inline]
       sb_start_intwrite include/linux/fs.h:2013 [inline]
       ocfs2_start_trans+0x267/0x6c0 fs/ocfs2/journal.c:372
       ocfs2_acquire_dquot+0x66e/0xb10 fs/ocfs2/quota_global.c:848
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       dquot_set_dqblk+0x27/0xf90 fs/quota/dquot.c:2833
       quota_setquota+0x4ac/0x530 fs/quota/quota.c:310
       __do_sys_quotactl fs/quota/quota.c:960 [inline]
       __se_sys_quotactl+0x295/0x6b0 fs/quota/quota.c:916
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&ocfs2_quota_ip_alloc_sem_key){++++}-{3:3}:
       down_write+0x36/0x60 kernel/locking/rwsem.c:1573
       ocfs2_create_local_dquot+0x1a0/0x1790 fs/ocfs2/quota_local.c:1224
       ocfs2_acquire_dquot+0x7ae/0xb10 fs/ocfs2/quota_global.c:871
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       dquot_set_dqblk+0x27/0xf90 fs/quota/dquot.c:2833
       quota_setquota+0x4ac/0x530 fs/quota/quota.c:310
       __do_sys_quotactl fs/quota/quota.c:960 [inline]
       __se_sys_quotactl+0x295/0x6b0 fs/quota/quota.c:916
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&dquot->dq_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain kernel/locking/lockdep.c:3825 [inline]
       __lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049
       lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x120/0xaf0 kernel/locking/mutex.c:747
       wait_on_dquot fs/quota/dquot.c:356 [inline]
       dqget+0x6f8/0xeb0 fs/quota/dquot.c:983
       dquot_transfer+0x391/0x820 fs/quota/dquot.c:2150
       ext4_setattr+0x93d/0x19f0 fs/ext4/inode.c:5502
       notify_change+0xc74/0xf40 fs/attr.c:499
       chown_common+0x486/0x620 fs/open.c:736
       do_fchownat+0x164/0x270 fs/open.c:767
       __do_sys_chown fs/open.c:787 [inline]
       __se_sys_chown fs/open.c:785 [inline]
       __x64_sys_chown+0x7e/0x90 fs/open.c:785
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  &dquot->dq_lock --> jbd2_handle --> &ei->xattr_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->xattr_sem);
                               lock(jbd2_handle);
                               lock(&ei->xattr_sem);
  lock(&dquot->dq_lock);

 *** DEADLOCK ***

3 locks held by syz.3.13039/1380:
 #0: ffff88801e360460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:393
 #1: ffff8880253e3628 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff8880253e3628 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: chown_common+0x320/0x620 fs/open.c:726
 #2: ffff8880253e32f0 (&ei->xattr_sem){++++}-{3:3}, at: ext4_setattr+0x92a/0x19f0 fs/ext4/inode.c:5501

stack backtrace:
CPU: 0 PID: 1380 Comm: syz.3.13039 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x2cf8/0x7c50 kernel/locking/lockdep.c:5049
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x120/0xaf0 kernel/locking/mutex.c:747
 wait_on_dquot fs/quota/dquot.c:356 [inline]
 dqget+0x6f8/0xeb0 fs/quota/dquot.c:983
 dquot_transfer+0x391/0x820 fs/quota/dquot.c:2150
 ext4_setattr+0x93d/0x19f0 fs/ext4/inode.c:5502
 notify_change+0xc74/0xf40 fs/attr.c:499
 chown_common+0x486/0x620 fs/open.c:736
 do_fchownat+0x164/0x270 fs/open.c:767
 __do_sys_chown fs/open.c:787 [inline]
 __se_sys_chown fs/open.c:785 [inline]
 __x64_sys_chown+0x7e/0x90 fs/open.c:785
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f8a01f8efc9
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:00007f8a02f13038 EFLAGS: 00000246 ORIG_RAX: 000000000000005c
RAX: ffffffffffffffda RBX: 00007f8a021e5fa0 RCX: 00007f8a01f8efc9
RDX: 0000000000000000 RSI: 000000000000ee00 RDI: 0000200000000240
RBP: 00007f8a02011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8a021e6038 R14: 00007f8a021e5fa0 R15: 00007fff9bb96918
 </TASK>

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/17 22:02 linux-6.1.y c2fda4b3f577 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/10/15 16:48 linux-6.1.y c2fda4b3f577 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/09/29 11:21 linux-6.1.y 7b34dc04e4ff 86341da6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/09/19 15:47 linux-6.1.y 363a599da6d9 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/09/02 13:25 linux-6.1.y f89b6e15694c 96a211bc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/08/07 10:40 linux-6.1.y 3594f306da12 04cffc22 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/06/30 17:33 linux-6.1.y 7e69c33e4858 6e83b42d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
2025/10/22 18:00 linux-6.1.y 8e6e2188d949 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in dqget
2025/08/28 15:29 linux-6.1.y f89b6e15694c e12e5ba4 .config console log report info ci2-linux-6-1-kasan-arm64 possible deadlock in dqget
2025/08/22 03:31 linux-6.1.y 0bc96de781b4 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in dqget
2025/07/31 15:59 linux-6.1.y 3594f306da12 0c075d67 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in dqget
* Struck through repros no longer work on HEAD.