possible deadlock in dqget

Status: auto-obsoleted due to no activity on 2025/05/07 22:20
Reported-by: syzbot+efbda23daeff0ba787cd@syzkaller.appspotmail.com
First crash: 555d, last: 555d
▶ ▼ 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 149d 412d 0/2 auto-obsoleted due to no activity on 2026/06/18 06:57
upstream possible deadlock in dqget ocfs2 ext4 4 syz, C error 100357 220d 674d 29/29 fixed on 2026/01/07 12:29
linux-5.15 possible deadlock in dqget 4 1 194d 194d 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 52d 194d 0/29 upstream: reported on 2026/01/24 00:53
linux-6.1 possible deadlock in dqget (2) 4 11 287d 401d 0/3 auto-obsoleted due to no activity on 2026/01/30 18:00

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.1.127-syzkaller #0 Not tainted
------------------------------------------------------
syz.3.11280/30035 is trying to acquire lock:
ffff888052ddfca8 (&dquot->dq_lock){+.+.}-{3:3}, at: wait_on_dquot fs/quota/dquot.c:356 [inline]
ffff888052ddfca8 (&dquot->dq_lock){+.+.}-{3:3}, at: dqget+0x6dc/0xe90 fs/quota/dquot.c:983

but task is already holding lock:
ffff888052e2b2f0 (&ei->xattr_sem){++++}-{3:3}, at: ext4_setattr+0xbbb/0x1a00 fs/ext4/inode.c:5471

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&ei->xattr_sem){++++}-{3:3}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       down_read+0xad/0xa30 kernel/locking/rwsem.c:1520
       ext4_setattr+0xbbb/0x1a00 fs/ext4/inode.c:5471
       notify_change+0xce3/0xfc0 fs/attr.c:499
       chown_common+0x5aa/0x900 fs/open.c:736
       do_fchownat+0x169/0x240 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+0x3b/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #4 (jbd2_handle){++++}-{0:0}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       start_this_handle+0x1f71/0x21b0 fs/jbd2/transaction.c:463
       jbd2__journal_start+0x2d1/0x5c0 fs/jbd2/transaction.c:520
       jbd2_journal_start+0x25/0x30 fs/jbd2/transaction.c:559
       ocfs2_start_trans+0x3c0/0x6f0 fs/ocfs2/journal.c:354
       ocfs2_shutdown_local_alloc+0x214/0xa90 fs/ocfs2/localalloc.c:416
       ocfs2_dismount_volume+0x1fb/0x960 fs/ocfs2/super.c:1879
       generic_shutdown_super+0x130/0x340 fs/super.c:501
       kill_block_super+0x7a/0xe0 fs/super.c:1470
       deactivate_locked_super+0xa0/0x110 fs/super.c:332
       cleanup_mnt+0x490/0x520 fs/namespace.c:1186
       task_work_run+0x246/0x300 kernel/task_work.c:203
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       exit_to_user_mode_loop+0xde/0x100 kernel/entry/common.c:177
       exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
       __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
       syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
       do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:87
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #3 (&journal->j_trans_barrier){.+.+}-{3:3}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       down_read+0xad/0xa30 kernel/locking/rwsem.c:1520
       ocfs2_start_trans+0x3b5/0x6f0 fs/ocfs2/journal.c:352
       ocfs2_shutdown_local_alloc+0x214/0xa90 fs/ocfs2/localalloc.c:416
       ocfs2_dismount_volume+0x1fb/0x960 fs/ocfs2/super.c:1879
       generic_shutdown_super+0x130/0x340 fs/super.c:501
       kill_block_super+0x7a/0xe0 fs/super.c:1470
       deactivate_locked_super+0xa0/0x110 fs/super.c:332
       cleanup_mnt+0x490/0x520 fs/namespace.c:1186
       task_work_run+0x246/0x300 kernel/task_work.c:203
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       exit_to_user_mode_loop+0xde/0x100 kernel/entry/common.c:177
       exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
       __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
       syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
       do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:87
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (sb_internal#2){.+.+}-{0:0}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       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+0x2b0/0x6f0 fs/ocfs2/journal.c:350
       ocfs2_acquire_dquot+0x68c/0xb60 fs/ocfs2/quota_global.c:843
       dqget+0x762/0xe90 fs/quota/dquot.c:988
       __dquot_initialize+0x2d9/0xea0 fs/quota/dquot.c:1517
       ocfs2_get_init_inode+0x154/0x1c0 fs/ocfs2/namei.c:202
       ocfs2_mknod+0xe32/0x2e20 fs/ocfs2/namei.c:310
       ocfs2_mkdir+0x1c0/0x4e0 fs/ocfs2/namei.c:657
       vfs_mkdir+0x3b6/0x590 fs/namei.c:4106
       do_mkdirat+0x225/0x360 fs/namei.c:4131
       __do_sys_mkdirat fs/namei.c:4146 [inline]
       __se_sys_mkdirat fs/namei.c:4144 [inline]
       __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4144
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&ocfs2_quota_ip_alloc_sem_key){++++}-{3:3}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       down_write+0x36/0x60 kernel/locking/rwsem.c:1573
       ocfs2_create_local_dquot+0x1dc/0x1b50 fs/ocfs2/quota_local.c:1229
       ocfs2_acquire_dquot+0x7df/0xb60 fs/ocfs2/quota_global.c:866
       dqget+0x762/0xe90 fs/quota/dquot.c:988
       __dquot_initialize+0x2d9/0xea0 fs/quota/dquot.c:1517
       ocfs2_get_init_inode+0x154/0x1c0 fs/ocfs2/namei.c:202
       ocfs2_mknod+0xe32/0x2e20 fs/ocfs2/namei.c:310
       ocfs2_mkdir+0x1c0/0x4e0 fs/ocfs2/namei.c:657
       vfs_mkdir+0x3b6/0x590 fs/namei.c:4106
       do_mkdirat+0x225/0x360 fs/namei.c:4131
       __do_sys_mkdirat fs/namei.c:4146 [inline]
       __se_sys_mkdirat fs/namei.c:4144 [inline]
       __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4144
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 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+0x1661/0x5950 kernel/locking/lockdep.c:3825
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x132/0xd80 kernel/locking/mutex.c:747
       wait_on_dquot fs/quota/dquot.c:356 [inline]
       dqget+0x6dc/0xe90 fs/quota/dquot.c:983
       dquot_transfer+0x3a1/0x8a0 fs/quota/dquot.c:2150
       ext4_setattr+0xbd3/0x1a00 fs/ext4/inode.c:5472
       notify_change+0xce3/0xfc0 fs/attr.c:499
       chown_common+0x5aa/0x900 fs/open.c:736
       do_fchownat+0x169/0x240 fs/open.c:767
       __do_sys_lchown fs/open.c:792 [inline]
       __se_sys_lchown fs/open.c:790 [inline]
       __x64_sys_lchown+0x81/0x90 fs/open.c:790
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 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.3.11280/30035:
 #0: ffff88804b410460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:393
 #1: ffff888052e2b628 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff888052e2b628 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: chown_common+0x3e5/0x900 fs/open.c:726
 #2: ffff888052e2b2f0 (&ei->xattr_sem){++++}-{3:3}, at: ext4_setattr+0xbbb/0x1a00 fs/ext4/inode.c:5471

stack backtrace:
CPU: 0 PID: 30035 Comm: syz.3.11280 Not tainted 6.1.127-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2fa/0x3b0 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+0x1661/0x5950 kernel/locking/lockdep.c:3825
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
 lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x132/0xd80 kernel/locking/mutex.c:747
 wait_on_dquot fs/quota/dquot.c:356 [inline]
 dqget+0x6dc/0xe90 fs/quota/dquot.c:983
 dquot_transfer+0x3a1/0x8a0 fs/quota/dquot.c:2150
 ext4_setattr+0xbd3/0x1a00 fs/ext4/inode.c:5472
 notify_change+0xce3/0xfc0 fs/attr.c:499
 chown_common+0x5aa/0x900 fs/open.c:736
 do_fchownat+0x169/0x240 fs/open.c:767
 __do_sys_lchown fs/open.c:792 [inline]
 __se_sys_lchown fs/open.c:790 [inline]
 __x64_sys_lchown+0x81/0x90 fs/open.c:790
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fba1b18cd29
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:00007fba1bf0d038 EFLAGS: 00000246 ORIG_RAX: 000000000000005e
RAX: ffffffffffffffda RBX: 00007fba1b3a5fa0 RCX: 00007fba1b18cd29
RDX: ffffffffffffffff RSI: 000000000000ee00 RDI: 0000000020000140
RBP: 00007fba1b20e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fba1b3a5fa0 R15: 00007ffe4df15768
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/01/27 22:19 linux-6.1.y 75cefdf153f5 18070896 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in dqget
* Struck through repros no longer work on HEAD.