From: syzbot <syzbot+f0b58a1f5075a90dd9a5@syzkaller.appspotmail.com>
To: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
tytso@mit.edu
Subject: [syzbot] [ext4?] possible deadlock in ext4_xattr_set_handle (7)
Date: Thu, 13 Nov 2025 00:08:29 -0800 [thread overview]
Message-ID: <691591fd.a70a0220.3124cb.0020.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: 7bb4d6512545 Merge tag 'v6.18rc4-SMB-client-fixes' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=170350b4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e46b8a1c645465a9
dashboard link: https://syzkaller.appspot.com/bug?extid=f0b58a1f5075a90dd9a5
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ad654d5866e3/disk-7bb4d651.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7ad4d94f39b6/vmlinux-7bb4d651.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1fa5516b633d/bzImage-7bb4d651.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f0b58a1f5075a90dd9a5@syzkaller.appspotmail.com
EXT4-fs (loop8): mounted filesystem 76b65be2-f6da-4727-8c75-0525a5b65a09 r/w without journal. Quota mode: none.
ext4 filesystem being mounted at /81/mnt supports timestamps until 2038-01-19 (0x7fffffff)
fscrypt: AES-256-XTS using implementation "xts-aes-vaes-avx2"
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.8.1928/14101 is trying to acquire lock:
ffff8880494b9d78 (&ei->xattr_sem){++++}-{4:4}, at: ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
ffff8880494b9d78 (&ei->xattr_sem){++++}-{4:4}, at: ext4_xattr_set_handle+0x165/0x1590 fs/ext4/xattr.c:2367
but task is already holding lock:
ffff888031d78b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1808 [inline]
ffff888031d78b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2f3/0x1010 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}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
percpu_down_read_internal+0x48/0x1c0 include/linux/percpu-rwsem.h:53
percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
ext4_writepages_down_read fs/ext4/ext4.h:1796 [inline]
ext4_writepages+0x1cc/0x350 fs/ext4/inode.c:3024
do_writepages+0x32e/0x550 mm/page-writeback.c:2604
__writeback_single_inode+0x145/0xff0 fs/fs-writeback.c:1719
writeback_single_inode+0x1f9/0x6a0 fs/fs-writeback.c:1840
write_inode_now+0x160/0x1d0 fs/fs-writeback.c:2903
iput_final fs/inode.c:1901 [inline]
iput+0x830/0xc50 fs/inode.c:1966
ext4_xattr_block_set+0x1fce/0x2ac0 fs/ext4/xattr.c:2199
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+0x12da/0x1ea0 fs/ext4/xattr.c:2827
__ext4_expand_extra_isize+0x30d/0x400 fs/ext4/inode.c:6364
ext4_try_to_expand_extra_isize fs/ext4/inode.c:6407 [inline]
__ext4_mark_inode_dirty+0x46c/0x700 fs/ext4/inode.c:6485
ext4_evict_inode+0x80d/0xee0 fs/ext4/inode.c:254
evict+0x504/0x9c0 fs/inode.c:810
ext4_orphan_cleanup+0xc20/0x1460 fs/ext4/orphan.c:470
__ext4_fill_super fs/ext4/super.c:5617 [inline]
ext4_fill_super+0x5920/0x61e0 fs/ext4/super.c:5736
get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
vfs_get_tree+0x92/0x2b0 fs/super.c:1751
fc_mount fs/namespace.c:1208 [inline]
do_new_mount_fc fs/namespace.c:3651 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3727
do_mount fs/namespace.c:4050 [inline]
__do_sys_mount fs/namespace.c:4238 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4215
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&ei->xattr_sem){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
ext4_xattr_set_handle+0x165/0x1590 fs/ext4/xattr.c:2367
ext4_set_context+0x21b/0x550 fs/ext4/crypto.c:166
fscrypt_set_context+0x38a/0x460 fs/crypto/policy.c:791
__ext4_new_inode+0x3143/0x3cb0 fs/ext4/ialloc.c:1315
ext4_ext_migrate+0x69f/0x1010 fs/ext4/migrate.c:456
ext4_ioctl_setflags fs/ext4/ioctl.c:705 [inline]
ext4_fileattr_set+0xeaf/0x1630 fs/ext4/ioctl.c:1024
vfs_fileattr_set+0x932/0xb90 fs/file_attr.c:298
ioctl_setflags+0x180/0x1e0 fs/file_attr.c:334
do_vfs_ioctl+0x8ed/0x1430 fs/ioctl.c:560
__do_sys_ioctl fs/ioctl.c:595 [inline]
__se_sys_ioctl+0x82/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
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.8.1928/14101:
#0: ffff888031d7e420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write_file+0x60/0x200 fs/namespace.c:552
#1: ffff8880494bd9f0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
#1: ffff8880494bd9f0 (&type->i_mutex_dir_key#3){++++}-{4:4}, at: vfs_fileattr_set+0x14e/0xb90 fs/file_attr.c:278
#2: ffff888031d78b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1808 [inline]
#2: ffff888031d78b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2f3/0x1010 fs/ext4/migrate.c:438
stack backtrace:
CPU: 0 UID: 0 PID: 14101 Comm: syz.8.1928 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
ext4_write_lock_xattr fs/ext4/xattr.h:157 [inline]
ext4_xattr_set_handle+0x165/0x1590 fs/ext4/xattr.c:2367
ext4_set_context+0x21b/0x550 fs/ext4/crypto.c:166
fscrypt_set_context+0x38a/0x460 fs/crypto/policy.c:791
__ext4_new_inode+0x3143/0x3cb0 fs/ext4/ialloc.c:1315
ext4_ext_migrate+0x69f/0x1010 fs/ext4/migrate.c:456
ext4_ioctl_setflags fs/ext4/ioctl.c:705 [inline]
ext4_fileattr_set+0xeaf/0x1630 fs/ext4/ioctl.c:1024
vfs_fileattr_set+0x932/0xb90 fs/file_attr.c:298
ioctl_setflags+0x180/0x1e0 fs/file_attr.c:334
do_vfs_ioctl+0x8ed/0x1430 fs/ioctl.c:560
__do_sys_ioctl fs/ioctl.c:595 [inline]
__se_sys_ioctl+0x82/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1f39f8f6c9
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:00007f1f3ade0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1f3a1e5fa0 RCX: 00007f1f39f8f6c9
RDX: 0000200000000080 RSI: 0000000040086602 RDI: 0000000000000004
RBP: 00007f1f3a011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1f3a1e6038 R14: 00007f1f3a1e5fa0 R15: 00007fffb7f49f38
</TASK>
EXT4-fs error (device loop8): ext4_validate_block_bitmap:423: comm syz.8.1928: bg 0: bad block bitmap checksum
---
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next reply other threads:[~2025-11-13 8:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-13 8:08 syzbot [this message]
2025-12-21 18:39 ` [syzbot] [ext4?] possible deadlock in ext4_xattr_set_handle (7) syzbot
2026-06-09 8:41 ` Forwarded: test syzbot
[not found] <36795559-b70e-4c03-b547-a355ca7f20e9@windriver.com>
2026-06-09 9:48 ` [syzbot] [ext4?] possible deadlock in ext4_xattr_set_handle (7) syzbot
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