* [syzbot] [fs?] possible deadlock in v2_write_dquot
@ 2026-10-22 22:33 syzbot
0 siblings, 0 replies; only message in thread
From: syzbot @ 2026-10-22 22:33 UTC (permalink / raw)
To: jack, linux-fsdevel, linux-kernel, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: a0ff06b3a7bd Merge tag 'firewire-fixes-7.3-final' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13a993a9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c4b098695335c89f
dashboard link: https://syzkaller.appspot.com/bug?extid=75d986c18cef4710fc85
compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2a3b826702d4/disk-a0ff06b3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6b5a43d8b46c/vmlinux-a0ff06b3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3a84903a147f/bzImage-a0ff06b3.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+75d986c18cef4710fc85@syzkaller.appspotmail.com
EXT4-fs (loop5): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /1334/file0 supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.5.7752/28220 is trying to acquire lock:
ffff8880535c6248 (&s->s_dquot.dqio_sem){++++}-{4:4}, at: v2_write_dquot+0xab/0x260 fs/quota/quota_v2.c:367
but task is already holding lock:
ffff88805537bca0 (&dquot->dq_lock){+.+.}-{4:4}, at: dquot_acquire+0x67/0x620 fs/quota/dquot.c:486
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #9 (&dquot->dq_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
wait_on_dquot fs/quota/dquot.c:357 [inline]
dqget+0x69d/0xbd0 fs/quota/dquot.c:997
__dquot_initialize+0x3c8/0xd40 fs/quota/dquot.c:1462
__ext4_new_inode+0x7ed/0x3ec0 fs/ext4/ialloc.c:1004
ext4_xattr_inode_create fs/ext4/xattr.c:1494 [inline]
ext4_xattr_inode_lookup_create+0xb1e/0x1d70 fs/ext4/xattr.c:1604
ext4_xattr_block_set+0x223/0x29a0 fs/ext4/xattr.c:1924
ext4_xattr_set_handle+0xed9/0x15f0 fs/ext4/xattr.c:2461
ext4_xattr_set+0x257/0x340 fs/ext4/xattr.c:2563
__vfs_setxattr+0x442/0x480 fs/xattr.c:223
__vfs_setxattr_noperm+0x12a/0x660 fs/xattr.c:257
vfs_setxattr+0x163/0x360 fs/xattr.c:344
do_setxattr fs/xattr.c:662 [inline]
filename_setxattr+0x296/0x630 fs/xattr.c:690
path_setxattrat+0x408/0x450 fs/xattr.c:734
__do_sys_setxattr fs/xattr.c:768 [inline]
__se_sys_setxattr fs/xattr.c:764 [inline]
__x64_sys_setxattr+0xbc/0xe0 fs/xattr.c:764
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
-> #8 (&ei->xattr_sem){++++}-{4:4}:
down_write+0x96/0x200 kernel/locking/rwsem.c:1631
ext4_write_lock_xattr fs/ext4/xattr.h:152 [inline]
ext4_inline_data_truncate+0x1cf/0xbd0 fs/ext4/inline.c:1882
ext4_truncate+0x444/0x1110 fs/ext4/inode.c:4650
ext4_setattr+0x1147/0x1df0 fs/ext4/inode.c:6220
notify_change+0xbba/0xea0 fs/attr.c:556
do_truncate+0x1c2/0x250 fs/open.c:68
handle_truncate fs/namei.c:4300 [inline]
do_open fs/namei.c:4840 [inline]
path_openat+0x185e/0x2090 fs/namei.c:4999
do_file_open+0x23e/0x4a0 fs/namei.c:5028
do_sys_openat2+0x115/0x200 fs/open.c:1417
do_sys_open fs/open.c:1423 [inline]
__do_sys_creat fs/open.c:1501 [inline]
__se_sys_creat fs/open.c:1495 [inline]
__x64_sys_creat+0x8f/0xc0 fs/open.c:1495
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
-> #7 (mapping.invalidate_lock#2){++++}-{4:4}:
down_read+0x4a/0x330 kernel/locking/rwsem.c:1574
filemap_invalidate_lock_shared include/linux/fs.h:1089 [inline]
do_page_cache_ra mm/readahead.c:347 [inline]
page_cache_ra_order+0xb37/0xee0 mm/readahead.c:558
do_sync_mmap_readahead+0x75e/0x990 mm/filemap.c:3443
filemap_fault+0x7d9/0x13b0 mm/filemap.c:3597
__do_fault+0x138/0x2a0 mm/memory.c:5565
do_read_fault mm/memory.c:6000 [inline]
do_fault mm/memory.c:6134 [inline]
do_pte_missing+0x2215/0x34b0 mm/memory.c:4700
handle_pte_fault mm/memory.c:6558 [inline]
__handle_mm_fault mm/memory.c:6707 [inline]
handle_mm_fault+0x1a53/0x3750 mm/memory.c:6876
do_user_addr_fault+0x746/0x1340 arch/x86/mm/fault.c:1394
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
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_from_user arch/x86/include/asm/uaccess_64.h:141 [inline]
copy_from_user_iter lib/iov_iter.c:67 [inline]
iterate_ubuf include/linux/iov_iter.h:30 [inline]
iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
iterate_and_advance include/linux/iov_iter.h:330 [inline]
__copy_from_iter lib/iov_iter.c:261 [inline]
_copy_from_iter+0x216/0x1660 lib/iov_iter.c:272
copy_from_iter include/linux/uio.h:228 [inline]
copy_from_iter_full include/linux/uio.h:245 [inline]
skb_do_copy_data_nocache include/net/sock.h:2329 [inline]
skb_copy_to_page_nocache include/net/sock.h:2355 [inline]
tcp_sendmsg_locked+0x20cf/0x5400 net/ipv4/tcp.c:1310
tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1451
sock_sendmsg_nosec+0x10e/0x180 net/socket.c:801
__sock_sendmsg net/socket.c:815 [inline]
sock_write_iter+0x2de/0x3e0 net/socket.c:1266
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
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
-> #6 (sk_lock-AF_INET){+.+.}-{0:0}:
lock_sock_nested+0x41/0x100 net/core/sock.c:3837
lock_sock include/net/sock.h:1713 [inline]
inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:913
nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:319
recv_work+0x1cee/0x1e10 drivers/block/nbd.c:1030
process_one_work kernel/workqueue.c:3396 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207
blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2130
__blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
__blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2545
process_one_work kernel/workqueue.c:3396 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #4 (&cmd->lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199
blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2130
__blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
__blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2545
process_one_work kernel/workqueue.c:3396 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #3 (set->srcu){.+.+}-{0:0}:
srcu_lock_sync include/linux/srcu.h:210 [inline]
__synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1462
elevator_switch+0x1e8/0x7b0 block/elevator.c:576
elevator_change+0x2fa/0x480 block/elevator.c:681
elevator_set_default+0x375/0x440 block/elevator.c:754
blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:992
__add_disk+0x6b8/0xdb0 block/genhd.c:531
add_disk_fwnode+0x100/0x3a0 block/genhd.c:600
add_disk include/linux/blkdev.h:798 [inline]
nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026
nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743
do_one_initcall+0x250/0x870 init/main.c:1362
do_initcall_level+0x10a/0x1a0 init/main.c:1424
do_initcalls+0x59/0xa0 init/main.c:1440
kernel_init_freeable+0x29d/0x3e0 init/main.c:1675
kernel_init+0x22/0x1d0 init/main.c:1565
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #2 (&q->elevator_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
elevator_change+0x1af/0x480 block/elevator.c:679
elv_iosched_store+0x504/0x630 block/elevator.c:826
queue_attr_store+0x207/0x2b0 block/blk-sysfs.c:906
kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
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 (&q->q_usage_counter(io)#17){++++}-{0:0}:
bio_queue_enter block/blk.h:95 [inline]
blk_mq_submit_bio+0x7a7/0x2bb0 block/blk-mq.c:3138
__submit_bio_noacct_mq block/blk-core.c:756 [inline]
submit_bio_noacct_nocheck+0x2f4/0xa40 block/blk-core.c:790
__ext4_read_bh fs/ext4/super.c:181 [inline]
ext4_read_bh+0x182/0x230 fs/ext4/super.c:206
ext4_bread+0x12d/0x180 fs/ext4/inode.c:1060
ext4_quota_read+0x189/0x390 fs/ext4/super.c:7397
read_blk fs/quota/quota_tree.c:61 [inline]
find_tree_dqentry+0x1fc/0x1090 fs/quota/quota_tree.c:671
find_tree_dqentry+0x6c0/0x1090 fs/quota/quota_tree.c:698
find_tree_dqentry+0x6c0/0x1090 fs/quota/quota_tree.c:698
find_tree_dqentry+0x6c0/0x1090 fs/quota/quota_tree.c:698
find_dqentry fs/quota/quota_tree.c:716 [inline]
qtree_read_dquot+0x5ac/0x8a0 fs/quota/quota_tree.c:736
v2_read_dquot+0x117/0x1d0 fs/quota/quota_v2.c:344
dquot_acquire+0x183/0x620 fs/quota/dquot.c:489
ext4_acquire_dquot+0x2f0/0x4e0 fs/ext4/super.c:7075
dqget+0x725/0xbd0 fs/quota/dquot.c:1002
__dquot_initialize+0x33a/0xd40 fs/quota/dquot.c:1462
ext4_rename fs/ext4/namei.c:3831 [inline]
ext4_rename2+0x758/0x3270 fs/ext4/namei.c:4218
vfs_rename+0xbd9/0xef0 fs/namei.c:6207
filename_renameat2+0x533/0x9a0 fs/namei.c:6325
__do_sys_renameat2 fs/namei.c:6354 [inline]
__se_sys_renameat2+0x5a/0x2c0 fs/namei.c:6349
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 (&s->s_dquot.dqio_sem){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3209 [inline]
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
down_write+0x96/0x200 kernel/locking/rwsem.c:1631
v2_write_dquot+0xab/0x260 fs/quota/quota_v2.c:367
dquot_acquire+0x328/0x620 fs/quota/dquot.c:498
ext4_acquire_dquot+0x2f0/0x4e0 fs/ext4/super.c:7075
dqget+0x725/0xbd0 fs/quota/dquot.c:1002
dquot_set_dqblk+0x2b/0xfd0 fs/quota/dquot.c:2777
quota_setquota+0x4e0/0x590 fs/quota/quota.c:310
__do_sys_quotactl fs/quota/quota.c:961 [inline]
__se_sys_quotactl+0x2cc/0x9f0 fs/quota/quota.c:917
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:
&s->s_dquot.dqio_sem --> &ei->xattr_sem --> &dquot->dq_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&dquot->dq_lock);
lock(&ei->xattr_sem);
lock(&dquot->dq_lock);
lock(&s->s_dquot.dqio_sem);
*** DEADLOCK ***
locks held by syz.5.7752/28220: 2, last CPU#0:
#0: ffff8880535c60e8 (&type->s_umount_key#33){++++}-{4:4}, at: __super_lock fs/super.c:62 [inline]
#0: ffff8880535c60e8 (&type->s_umount_key#33){++++}-{4:4}, at: super_lock+0x2d6/0x3d0 fs/super.c:124
#1: ffff88805537bca0 (&dquot->dq_lock){+.+.}-{4:4}, at: dquot_acquire+0x67/0x620 fs/quota/dquot.c:486
stack backtrace:
CPU: 0 UID: 0 PID: 28220 Comm: syz.5.7752 Tainted: G L syzkaller #0 PREEMPT(lazy)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
check_prev_add kernel/locking/lockdep.c:3209 [inline]
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
down_write+0x96/0x200 kernel/locking/rwsem.c:1631
v2_write_dquot+0xab/0x260 fs/quota/quota_v2.c:367
dquot_acquire+0x328/0x620 fs/quota/dquot.c:498
ext4_acquire_dquot+0x2f0/0x4e0 fs/ext4/super.c:7075
dqget+0x725/0xbd0 fs/quota/dquot.c:1002
dquot_set_dqblk+0x2b/0xfd0 fs/quota/dquot.c:2777
quota_setquota+0x4e0/0x590 fs/quota/quota.c:310
__do_sys_quotactl fs/quota/quota.c:961 [inline]
__se_sys_quotactl+0x2cc/0x9f0 fs/quota/quota.c:917
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: 0033:0x7ffb1039e559
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:00007ffb11205028 EFLAGS: 00000246 ORIG_RAX: 00000000000000b3
RAX: ffffffffffffffda RBX: 00007ffb10625fa0 RCX: 00007ffb1039e559
RDX: 0000000000000000 RSI: 0000200000000000 RDI: ffffffff80000801
RBP: 00007ffb10435ab8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000000100 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffb10626038 R14: 00007ffb10625fa0 R15: 00007fff0c429e18
</TASK>
---
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2026-10-22 22:33 [syzbot] [fs?] possible deadlock in v2_write_dquot syzbot
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