syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.301/5344 is trying to acquire lock:
ffff888062bea8a8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_xattr_get+0xfc/0x800 fs/ext4/xattr.c:654

but task is already holding lock:
ffff888061e94bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2d7/0xe60 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+0x46/0x1b0 include/linux/percpu-rwsem.h:51
       ext4_writepages+0x20f/0x2df0 fs/ext4/inode.c:2689
       do_writepages+0x476/0x6e0 mm/page-writeback.c:2386
       __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
       writeback_single_inode+0x3cb/0x8e0 fs/fs-writeback.c:1770
       write_inode_now+0x23b/0x2c0 fs/fs-writeback.c:2817
       iput_final fs/inode.c:1756 [inline]
       iput+0x5ab/0x8a0 fs/inode.c:1795
       ext4_xattr_set_entry+0x34f4/0x3ea0 fs/ext4/xattr.c:1825
       ext4_xattr_block_set+0x4fd/0x2d20 fs/ext4/xattr.c:1924
       ext4_xattr_move_to_block fs/ext4/xattr.c:2618 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2693 [inline]
       ext4_expand_extra_isize_ea+0xf3f/0x19b0 fs/ext4/xattr.c:2781
       __ext4_expand_extra_isize+0x301/0x3e0 fs/ext4/inode.c:5905
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:5948 [inline]
       __ext4_mark_inode_dirty+0x469/0x700 fs/ext4/inode.c:6026
       ext4_evict_inode+0xa8d/0x1090 fs/ext4/inode.c:282
       evict+0x4c9/0x8d0 fs/inode.c:647
       ext4_orphan_cleanup+0xad2/0x1320 fs/ext4/orphan.c:472
       ext4_fill_super+0x8e25/0x95a0 fs/ext4/super.c:5000
       mount_bdev+0x287/0x3c0 fs/super.c:1400
       legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
       vfs_get_tree+0x88/0x270 fs/super.c:1530
       do_new_mount+0x24a/0xa40 fs/namespace.c:3034
       do_mount fs/namespace.c:3377 [inline]
       __do_sys_mount fs/namespace.c:3585 [inline]
       __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3562
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&ei->xattr_sem){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       ext4_xattr_get+0xfc/0x800 fs/ext4/xattr.c:654
       ext4_get_acl+0x80/0x660 fs/ext4/acl.c:165
       get_acl+0x154/0x250 fs/posix_acl.c:153
       posix_acl_create+0x124/0x430 fs/posix_acl.c:632
       ext4_init_acl+0xb7/0x330 fs/ext4/acl.c:283
       __ext4_new_inode+0x2eb3/0x3a40 fs/ext4/ialloc.c:1328
       ext4_ext_migrate+0x5f1/0xe60 fs/ext4/migrate.c:456
       __ext4_ioctl fs/ext4/ioctl.c:1028 [inline]
       ext4_ioctl+0x1a84/0x3820 fs/ext4/ioctl.c:1282
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

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.4.301/5344:
 #0: ffff88807db0e460 (sb_writers#5){++++}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
 #1: ffff88805f172bd0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff88805f172bd0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1027 [inline]
 #1: ffff88805f172bd0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_ioctl+0x1a7c/0x3820 fs/ext4/ioctl.c:1282
 #2: ffff888061e94bd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x2d7/0xe60 fs/ext4/migrate.c:438

stack backtrace:
CPU: 0 PID: 5344 Comm: syz.4.301 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c42/0x7d10 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
 ext4_xattr_get+0xfc/0x800 fs/ext4/xattr.c:654
 ext4_get_acl+0x80/0x660 fs/ext4/acl.c:165
 get_acl+0x154/0x250 fs/posix_acl.c:153
 posix_acl_create+0x124/0x430 fs/posix_acl.c:632
 ext4_init_acl+0xb7/0x330 fs/ext4/acl.c:283
 __ext4_new_inode+0x2eb3/0x3a40 fs/ext4/ialloc.c:1328
 ext4_ext_migrate+0x5f1/0xe60 fs/ext4/migrate.c:456
 __ext4_ioctl fs/ext4/ioctl.c:1028 [inline]
 ext4_ioctl+0x1a84/0x3820 fs/ext4/ioctl.c:1282
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fb3abc20799
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:00007fb3a9e59028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb3abe9a090 RCX: 00007fb3abc20799
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000006
RBP: 00007fb3abcb6bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb3abe9a128 R14: 00007fb3abe9a090 R15: 00007ffe060ccc98
 </TASK>