Kernel bug: possible deadlock in dqget
Subsystem: ext4, ocfs2
Status: fixed

Crash report:
loop0: detected capacity change from 0 to 1024
loop0: detected capacity change from 0 to 512
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /root/syzkaller.LCBzqe/9/file0 supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc7-syzkaller-00112-geccf6f2f6ab9 #0 Not tainted
------------------------------------------------------
syz-executor803/5851 is trying to acquire lock:
ffff8880778c6268 (&dquot->dq_lock){+.+.}-{4:4}, at: wait_on_dquot fs/quota/dquot.c:354 [inline]
ffff8880778c6268 (&dquot->dq_lock){+.+.}-{4:4}, at: dqget+0x72a/0xf10 fs/quota/dquot.c:972

but task is already holding lock:
ffff88807795edc0 (&ei->xattr_sem){++++}-{4:4}, at: ext4_setattr+0x855/0x1bd0 fs/ext4/inode.c:5459

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&ei->xattr_sem){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
       ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
       ext4_xattr_set_handle+0x165/0x1590 fs/ext4/xattr.c:2362
       ext4_initxattrs+0x9f/0x110 fs/ext4/xattr_security.c:44
       security_inode_init_security+0x2a0/0x3f0 security/security.c:1852
       __ext4_new_inode+0x3257/0x3bd0 fs/ext4/ialloc.c:1326
       ext4_create+0x22d/0x460 fs/ext4/namei.c:2824
       lookup_open fs/namei.c:3701 [inline]
       open_last_lookups fs/namei.c:3800 [inline]
       path_openat+0x14f1/0x3830 fs/namei.c:4036
       do_filp_open+0x1fa/0x410 fs/namei.c:4066
       do_sys_openat2+0x121/0x1c0 fs/open.c:1429
       do_sys_open fs/open.c:1444 [inline]
       __do_sys_openat fs/open.c:1460 [inline]
       __se_sys_openat fs/open.c:1455 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1455
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (jbd2_handle){++++}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       start_this_handle+0x1fa7/0x21c0 fs/jbd2/transaction.c:444
       jbd2__journal_start+0x2c1/0x5b0 fs/jbd2/transaction.c:501
       jbd2_journal_start+0x2a/0x40 fs/jbd2/transaction.c:540
       ocfs2_start_trans+0x376/0x6d0 fs/ocfs2/journal.c:374
       ocfs2_modify_bh+0xe8/0x470 fs/ocfs2/quota_local.c:101
       ocfs2_local_read_info+0x1465/0x17e0 fs/ocfs2/quota_local.c:767
       dquot_load_quota_sb+0x78e/0xbd0 fs/quota/dquot.c:2459
       dquot_load_quota_inode+0x2e1/0x5d0 fs/quota/dquot.c:2496
       ocfs2_enable_quotas+0x1c6/0x450 fs/ocfs2/super.c:930
       ocfs2_fill_super+0x5115/0x63d0 fs/ocfs2/super.c:1140
       get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1636
       vfs_get_tree+0x92/0x2b0 fs/super.c:1759
       do_new_mount+0x24a/0xa40 fs/namespace.c:3881
       do_mount fs/namespace.c:4221 [inline]
       __do_sys_mount fs/namespace.c:4432 [inline]
       __se_sys_mount+0x317/0x410 fs/namespace.c:4409
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&journal->j_trans_barrier){.+.+}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1524
       ocfs2_start_trans+0x36a/0x6d0 fs/ocfs2/journal.c:372
       ocfs2_modify_bh+0xe8/0x470 fs/ocfs2/quota_local.c:101
       ocfs2_local_read_info+0x1465/0x17e0 fs/ocfs2/quota_local.c:767
       dquot_load_quota_sb+0x78e/0xbd0 fs/quota/dquot.c:2459
       dquot_load_quota_inode+0x2e1/0x5d0 fs/quota/dquot.c:2496
       ocfs2_enable_quotas+0x1c6/0x450 fs/ocfs2/super.c:930
       ocfs2_fill_super+0x5115/0x63d0 fs/ocfs2/super.c:1140
       get_tree_bdev_flags+0x40b/0x4d0 fs/super.c:1636
       vfs_get_tree+0x92/0x2b0 fs/super.c:1759
       do_new_mount+0x24a/0xa40 fs/namespace.c:3881
       do_mount fs/namespace.c:4221 [inline]
       __do_sys_mount fs/namespace.c:4432 [inline]
       __se_sys_mount+0x317/0x410 fs/namespace.c:4409
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (sb_internal#2){.+.+}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
       __sb_start_write include/linux/fs.h:1783 [inline]
       sb_start_intwrite include/linux/fs.h:1966 [inline]
       ocfs2_start_trans+0x26b/0x6d0 fs/ocfs2/journal.c:370
       ocfs2_acquire_dquot+0x455/0xb30 fs/ocfs2/quota_global.c:860
       dqget+0x7ae/0xf10 fs/quota/dquot.c:977
       __dquot_initialize+0x3b3/0xcb0 fs/quota/dquot.c:1505
       ocfs2_get_init_inode+0x13b/0x1b0 fs/ocfs2/namei.c:202
       ocfs2_mknod+0x863/0x2050 fs/ocfs2/namei.c:310
       ocfs2_create+0x1a5/0x440 fs/ocfs2/namei.c:673
       lookup_open fs/namei.c:3701 [inline]
       open_last_lookups fs/namei.c:3800 [inline]
       path_openat+0x14f1/0x3830 fs/namei.c:4036
       do_filp_open+0x1fa/0x410 fs/namei.c:4066
       do_sys_openat2+0x121/0x1c0 fs/open.c:1429
       do_sys_open fs/open.c:1444 [inline]
       __do_sys_openat fs/open.c:1460 [inline]
       __se_sys_openat fs/open.c:1455 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1455
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&ocfs2_quota_ip_alloc_sem_key){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1577
       ocfs2_create_local_dquot+0x19d/0x1a40 fs/ocfs2/quota_local.c:1227
       ocfs2_acquire_dquot+0x80f/0xb30 fs/ocfs2/quota_global.c:883
       dqget+0x7ae/0xf10 fs/quota/dquot.c:977
       __dquot_initialize+0x3b3/0xcb0 fs/quota/dquot.c:1505
       ocfs2_get_init_inode+0x13b/0x1b0 fs/ocfs2/namei.c:202
       ocfs2_mknod+0x863/0x2050 fs/ocfs2/namei.c:310
       ocfs2_create+0x1a5/0x440 fs/ocfs2/namei.c:673
       lookup_open fs/namei.c:3701 [inline]
       open_last_lookups fs/namei.c:3800 [inline]
       path_openat+0x14f1/0x3830 fs/namei.c:4036
       do_filp_open+0x1fa/0x410 fs/namei.c:4066
       do_sys_openat2+0x121/0x1c0 fs/open.c:1429
       do_sys_open fs/open.c:1444 [inline]
       __do_sys_openat fs/open.c:1460 [inline]
       __se_sys_openat fs/open.c:1455 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1455
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&dquot->dq_lock){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
       __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       wait_on_dquot fs/quota/dquot.c:354 [inline]
       dqget+0x72a/0xf10 fs/quota/dquot.c:972
       dquot_transfer+0x2f8/0x6d0 fs/quota/dquot.c:2140
       ext4_setattr+0x865/0x1bd0 fs/ext4/inode.c:5460
       notify_change+0xb36/0xe40 fs/attr.c:552
       chown_common+0x3f9/0x5a0 fs/open.c:782
       vfs_fchown fs/open.c:850 [inline]
       ksys_fchown+0xea/0x160 fs/open.c:862
       __do_sys_fchown fs/open.c:867 [inline]
       __se_sys_fchown fs/open.c:865 [inline]
       __x64_sys_fchown+0x7a/0x90 fs/open.c:865
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 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:
  &dquot->dq_lock --> jbd2_handle --> &ei->xattr_sem

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by syz-executor803/5851:
 #0: ffff88801191e420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write_file+0x60/0x200 fs/namespace.c:600
 #1: ffff88807795f130 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: inode_lock include/linux/fs.h:867 [inline]
 #1: ffff88807795f130 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: chown_common+0x313/0x5a0 fs/open.c:772
 #2: ffff88807795edc0 (&ei->xattr_sem){++++}-{4:4}, at: ext4_setattr+0x855/0x1bd0 fs/ext4/inode.c:5459

stack backtrace:
CPU: 0 UID: 0 PID: 5851 Comm: syz-executor803 Not tainted 6.15.0-rc7-syzkaller-00112-geccf6f2f6ab9 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
 wait_on_dquot fs/quota/dquot.c:354 [inline]
 dqget+0x72a/0xf10 fs/quota/dquot.c:972
 dquot_transfer+0x2f8/0x6d0 fs/quota/dquot.c:2140
 ext4_setattr+0x865/0x1bd0 fs/ext4/inode.c:5460
 notify_change+0xb36/0xe40 fs/attr.c:552
 chown_common+0x3f9/0x5a0 fs/open.c:782
 vfs_fchown fs/open.c:850 [inline]
 ksys_fchown+0xea/0x160 fs/open.c:862
 __do_sys_fchown fs/open.c:867 [inline]
 __se_sys_fchown fs/open.c:865 [inline]
 __x64_sys_fchown+0x7a/0x90 fs/open.c:865
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1ae7d3b4a9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffccf1129f8 EFLAGS: 00000246 ORIG_RAX: 000000000000005d
RAX: ffffffffffffffda RBX: 0000200000004780 RCX: 00007f1ae7d3b4a9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00002000000000c0 R08: 0000200000000a80 R09: 00007ffccf112a30
R10: 0000000000000534 R11: 0000000000000246 R12: 00007ffccf112a1c
R13: 0000000000000009 R14: 431bde82d7b634db R15: 00007ffccf112a50
 </TASK>
EXT4-fs error (device loop0): ext4_search_dir:1476: inode #2: block 3: comm syz-executor803: bad entry in directory: rec_len is smaller than minimal - offset=16444, inode=113, rec_len=0, size=2048 fake=0