syzbot


possible deadlock in ext4_xattr_set_handle

Status: upstream: reported on 2026/05/12 19:17
Reported-by: syzbot+fccdae14434d56ae4932@syzkaller.appspotmail.com
First crash: 3d00h, last: 3d00h
Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in ext4_xattr_set_handle (5) ext4 4 72 689d 732d 0/29 auto-obsoleted due to no activity on 2024/09/03 19:27
upstream possible deadlock in ext4_xattr_set_handle (3) ext4 4 C 451 1049d 1206d 22/29 fixed on 2023/07/01 16:05
upstream possible deadlock in ext4_xattr_set_handle (7) ext4 4 C unreliable 213 2h39m 183d 0/29 upstream: reported C repro on 2025/11/13 08:08
upstream possible deadlock in ext4_xattr_set_handle (4) ext4 4 5 846d 966d 0/29 auto-obsoleted due to no activity on 2024/04/29 16:11
upstream possible deadlock in ext4_xattr_set_handle ext4 4 1 1669d 1665d 0/29 auto-closed as invalid on 2022/02/15 19:59
upstream possible deadlock in ext4_xattr_set_handle (6) ext4 4 50 569d 590d 0/29 auto-obsoleted due to no activity on 2025/01/01 12:48
upstream possible deadlock in ext4_xattr_set_handle (2) ext4 4 1 1404d 1403d 0/29 auto-obsoleted due to no activity on 2022/11/08 16:24
linux-5.15 possible deadlock in ext4_xattr_set_handle 4 C done 42 1072d 1165d 3/3 fixed on 2023/07/17 13:09
linux-4.19 possible deadlock in ext4_xattr_set_handle ext4 4 1 1197d 1197d 0/1 upstream: reported on 2023/02/03 16:43
linux-6.1 possible deadlock in ext4_xattr_set_handle 4 C done 15 1072d 1160d 3/3 fixed on 2023/07/17 13:09

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.1253/11542 is trying to acquire lock:
ffff88805c5a8ac8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:158 [inline]
ffff88805c5a8ac8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_xattr_set_handle+0x19d/0x14c0 fs/ext4/xattr.c:2367

but task is already holding lock:
ffff88802ff8ac58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1780 [inline]
ffff88802ff8ac58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x321/0x1080 fs/ext4/migrate.c:438

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sbi->s_writepages_rwsem){++++}-{0:0}:
       percpu_down_read+0x44/0x1a0 include/linux/percpu-rwsem.h:51
       ext4_writepages_down_read fs/ext4/ext4.h:1768 [inline]
       ext4_writepages+0x1a4/0x350 fs/ext4/inode.c:2808
       do_writepages+0x3b3/0x630 mm/page-writeback.c:2575
       __writeback_single_inode+0x153/0xec0 fs/fs-writeback.c:1635
       writeback_single_inode+0x21f/0x760 fs/fs-writeback.c:1756
       write_inode_now+0x183/0x210 fs/fs-writeback.c:2808
       iput_final fs/inode.c:1807 [inline]
       iput+0x5ae/0x920 fs/inode.c:1846
       ext4_xattr_block_set+0x249e/0x32b0 fs/ext4/xattr.c:2146
       ext4_xattr_move_to_block fs/ext4/xattr.c:2664 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2739 [inline]
       ext4_expand_extra_isize_ea+0x12c5/0x1e80 fs/ext4/xattr.c:2827
       __ext4_expand_extra_isize+0x306/0x400 fs/ext4/inode.c:5990
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6033 [inline]
       __ext4_mark_inode_dirty+0x45d/0x6e0 fs/ext4/inode.c:6111
       ext4_evict_inode+0x7f3/0xea0 fs/ext4/inode.c:254
       evict+0x4ca/0x8d0 fs/inode.c:705
       ext4_orphan_cleanup+0xbec/0x1420 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5621 [inline]
       ext4_fill_super+0x5eea/0x67b0 fs/ext4/super.c:5744
       get_tree_bdev+0x3f3/0x520 fs/super.c:1591
       vfs_get_tree+0x8c/0x280 fs/super.c:1764
       do_new_mount+0x24b/0xa40 fs/namespace.c:3386
       do_mount fs/namespace.c:3726 [inline]
       __do_sys_mount fs/namespace.c:3935 [inline]
       __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&ei->xattr_sem){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       down_write+0x97/0x200 kernel/locking/rwsem.c:1573
       ext4_write_lock_xattr fs/ext4/xattr.h:158 [inline]
       ext4_xattr_set_handle+0x19d/0x14c0 fs/ext4/xattr.c:2367
       ext4_set_context+0x230/0x560 fs/ext4/crypto.c:179
       fscrypt_set_context+0x1e6/0x280 fs/crypto/policy.c:761
       __ext4_new_inode+0x2eaa/0x3ac0 fs/ext4/ialloc.c:1326
       ext4_ext_migrate+0x6f0/0x1080 fs/ext4/migrate.c:456
       __ext4_ioctl fs/ext4/ioctl.c:1412 [inline]
       ext4_ioctl+0x1ee3/0x3b80 fs/ext4/ioctl.c:1630
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:871 [inline]
       __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->s_writepages_rwsem);
                               lock(&ei->xattr_sem);
                               lock(&sbi->s_writepages_rwsem);
  lock(&ei->xattr_sem);

 *** DEADLOCK ***

3 locks held by syz.3.1253/11542:
 #0: ffff88802ff8c418 (sb_writers#4){++++}-{0:0}, at: mnt_want_write_file+0x63/0x200 fs/namespace.c:456
 #1: ffff88805c5a8410 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #1: ffff88805c5a8410 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1411 [inline]
 #1: ffff88805c5a8410 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_ioctl+0x1edb/0x3b80 fs/ext4/ioctl.c:1630
 #2: ffff88802ff8ac58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1780 [inline]
 #2: ffff88802ff8ac58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x321/0x1080 fs/ext4/migrate.c:438

stack backtrace:
CPU: 1 PID: 11542 Comm: syz.3.1253 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2df1/0x7d40 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 down_write+0x97/0x200 kernel/locking/rwsem.c:1573
 ext4_write_lock_xattr fs/ext4/xattr.h:158 [inline]
 ext4_xattr_set_handle+0x19d/0x14c0 fs/ext4/xattr.c:2367
 ext4_set_context+0x230/0x560 fs/ext4/crypto.c:179
 fscrypt_set_context+0x1e6/0x280 fs/crypto/policy.c:761
 __ext4_new_inode+0x2eaa/0x3ac0 fs/ext4/ialloc.c:1326
 ext4_ext_migrate+0x6f0/0x1080 fs/ext4/migrate.c:456
 __ext4_ioctl fs/ext4/ioctl.c:1412 [inline]
 ext4_ioctl+0x1ee3/0x3b80 fs/ext4/ioctl.c:1630
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f178999cdd9
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:00007f178a895028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1789c16090 RCX: 00007f178999cdd9
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000004
RBP: 00007f1789a32d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1789c16128 R14: 00007f1789c16090 R15: 00007ffd3ecfd1a8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/12 19:16 linux-6.6.y 3b9f64db0496 07aeade5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in ext4_xattr_set_handle
* Struck through repros no longer work on HEAD.