syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.519/7278 is trying to acquire lock:
ffff88805c941ec8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
ffff88805c941ec8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1884

but task is already holding lock:
ffff88805ab7cbd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1767 [inline]
ffff88805ab7cbd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x170/0x2f0 fs/ext4/inode.c:2806

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:1767 [inline]
       ext4_writepages+0x170/0x2f0 fs/ext4/inode.c:2806
       do_writepages+0x3a2/0x600 mm/page-writeback.c:2575
       __writeback_single_inode+0x153/0xee0 fs/fs-writeback.c:1635
       writeback_single_inode+0x211/0x720 fs/fs-writeback.c:1756
       write_inode_now+0x161/0x1e0 fs/fs-writeback.c:2802
       iput_final fs/inode.c:1807 [inline]
       iput+0x5b2/0x920 fs/inode.c:1846
       ext4_xattr_block_set+0x273a/0x32a0 fs/ext4/xattr.c:2211
       ext4_xattr_move_to_block fs/ext4/xattr.c:2679 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2754 [inline]
       ext4_expand_extra_isize_ea+0x10ea/0x19e0 fs/ext4/xattr.c:2846
       __ext4_expand_extra_isize+0x306/0x400 fs/ext4/inode.c:5967
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6010 [inline]
       __ext4_mark_inode_dirty+0x45d/0x6e0 fs/ext4/inode.c:6088
       ext4_evict_inode+0x7ed/0xea0 fs/ext4/inode.c:252
       evict+0x486/0x870 fs/inode.c:705
       ext4_orphan_cleanup+0xbd4/0x1400 fs/ext4/orphan.c:470
       __ext4_fill_super fs/ext4/super.c:5601 [inline]
       ext4_fill_super+0x5de4/0x66c0 fs/ext4/super.c:5724
       get_tree_bdev+0x3e4/0x510 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+0x2da/0x3c0 fs/namespace.c:3912
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
       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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
       lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
       down_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
       ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
       ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1884
       ext4_do_writepages+0x4c2/0x38d0 fs/ext4/inode.c:2604
       ext4_writepages+0x1a8/0x2f0 fs/ext4/inode.c:2807
       do_writepages+0x3a2/0x600 mm/page-writeback.c:2575
       filemap_fdatawrite_wbc+0x122/0x180 mm/filemap.c:390
       __filemap_fdatawrite_range mm/filemap.c:423 [inline]
       __filemap_fdatawrite mm/filemap.c:429 [inline]
       filemap_flush+0xc5/0x120 mm/filemap.c:456
       ext4_release_file+0x82/0x310 fs/ext4/file.c:169
       __fput+0x234/0x970 fs/file_table.c:384
       task_work_run+0x1ce/0x250 kernel/task_work.c:239
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
       exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
       __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
       syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
       do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz.1.519/7278:
 #0: ffff88805ab7cbd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1767 [inline]
 #0: ffff88805ab7cbd8 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x170/0x2f0 fs/ext4/inode.c:2806

stack backtrace:
CPU: 0 PID: 7278 Comm: syz.1.519 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_noncircular+0x2bd/0x3c0 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+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 down_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
 ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
 ext4_destroy_inline_data+0x28/0xe0 fs/ext4/inline.c:1884
 ext4_do_writepages+0x4c2/0x38d0 fs/ext4/inode.c:2604
 ext4_writepages+0x1a8/0x2f0 fs/ext4/inode.c:2807
 do_writepages+0x3a2/0x600 mm/page-writeback.c:2575
 filemap_fdatawrite_wbc+0x122/0x180 mm/filemap.c:390
 __filemap_fdatawrite_range mm/filemap.c:423 [inline]
 __filemap_fdatawrite mm/filemap.c:429 [inline]
 filemap_flush+0xc5/0x120 mm/filemap.c:456
 ext4_release_file+0x82/0x310 fs/ext4/file.c:169
 __fput+0x234/0x970 fs/file_table.c:384
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb403f8f6c9
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:00007fffb938e1d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 0000000000024c79 RCX: 00007fb403f8f6c9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fb4041e7da0 R08: 0000000000000001 R09: 00000004b938e4cf
R10: 0000001b2d520000 R11: 0000000000000246 R12: 00007fb4041e5fac
R13: 00007fb4041e5fa0 R14: ffffffffffffffff R15: 00007fffb938e2f0
 </TASK>
EXT4-fs error (device loop1): ext4_mb_generate_buddy:1215: group 0, block bitmap and bg descriptor inconsistent: 25 vs 4278190105 free clusters
EXT4-fs (loop1): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 32 with error 28
EXT4-fs (loop1): This should not happen!! Data will be lost

EXT4-fs (loop1): Total free blocks count 0
EXT4-fs (loop1): Free/Dirty block details
EXT4-fs (loop1): free_blocks=68451041280
EXT4-fs (loop1): dirty_blocks=32
EXT4-fs (loop1): Block reservation details
EXT4-fs (loop1): i_reserved_data_blocks=2