syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.893/9383 is trying to acquire lock:
ffff8880a97e4610 (sb_internal){++++}-{0:0}, at: evict+0x3c2/0xad0 fs/inode.c:846

but task is already holding lock:
ffff888025da6b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1825 [inline]
ffff888025da6b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x3bf/0x2000 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_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       ext4_writepages_down_read fs/ext4/ext4.h:1813 [inline]
       ext4_writepages+0x21d/0x790 fs/ext4/inode.c:3018
       do_writepages+0x278/0x600 mm/page-writeback.c:2554
       __writeback_single_inode+0x164/0x13c0 fs/fs-writeback.c:1749
       writeback_single_inode+0x4d3/0xf30 fs/fs-writeback.c:1868
       write_inode_now+0x174/0x1f0 fs/fs-writeback.c:2953
       iput_final fs/inode.c:1956 [inline]
       iput.part.0+0x7f3/0xf50 fs/inode.c:2015
       iput+0x35/0x40 fs/inode.c:1981
       ext4_xattr_block_set+0x6f7/0x3660 fs/ext4/xattr.c:2204
       ext4_xattr_move_to_block fs/ext4/xattr.c:2669 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2744 [inline]
       ext4_expand_extra_isize_ea+0x17c6/0x1d70 fs/ext4/xattr.c:2832
       __ext4_expand_extra_isize+0x346/0x480 fs/ext4/inode.c:6297
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:6340 [inline]
       __ext4_mark_inode_dirty+0x693/0x8b0 fs/ext4/inode.c:6418
       ext4_evict_inode+0x860/0x17c0 fs/ext4/inode.c:255
       evict+0x3c2/0xad0 fs/inode.c:846
       iput_final fs/inode.c:1966 [inline]
       iput.part.0+0x605/0xf50 fs/inode.c:2015
       iput+0x35/0x40 fs/inode.c:1981
       ext4_orphan_cleanup+0x71e/0x11e0 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5668 [inline]
       ext4_fill_super+0x9009/0xb470 fs/ext4/super.c:5791
       get_tree_bdev_flags+0x38c/0x620 fs/super.c:1694
       vfs_get_tree+0x92/0x320 fs/super.c:1754
       fc_mount fs/namespace.c:1193 [inline]
       do_new_mount_fc fs/namespace.c:3760 [inline]
       do_new_mount fs/namespace.c:3836 [inline]
       path_mount+0x7d0/0x23d0 fs/namespace.c:4146
       do_mount fs/namespace.c:4159 [inline]
       __do_sys_mount fs/namespace.c:4348 [inline]
       __se_sys_mount fs/namespace.c:4325 [inline]
       __x64_sys_mount+0x293/0x310 fs/namespace.c:4325
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sb_internal){++++}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
       __sb_start_write include/linux/fs/super.h:19 [inline]
       sb_start_intwrite include/linux/fs/super.h:177 [inline]
       ext4_evict_inode+0xd3c/0x17c0 fs/ext4/inode.c:216
       evict+0x3c2/0xad0 fs/inode.c:846
       iput_final fs/inode.c:1966 [inline]
       iput.part.0+0x605/0xf50 fs/inode.c:2015
       iput+0x35/0x40 fs/inode.c:1981
       ext4_ext_migrate+0xd61/0x2000 fs/ext4/migrate.c:594
       __ext4_ioctl+0xd7e/0x42a0 fs/ext4/ioctl.c:1693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 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(sb_internal);
                               lock(&sbi->s_writepages_rwsem);
  rlock(sb_internal);

 *** DEADLOCK ***

3 locks held by syz.2.893/9383:
 #0: ffff8880a97e4420 (sb_writers#4){++++}-{0:0}, at: __ext4_ioctl+0xd4e/0x42a0 fs/ext4/ioctl.c:1683
 #1: ffff888083234708 (&sb->s_type->i_mutex_key#12){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline]
 #1: ffff888083234708 (&sb->s_type->i_mutex_key#12){++++}-{4:4}, at: __ext4_ioctl+0xd76/0x42a0 fs/ext4/ioctl.c:1692
 #2: ffff888025da6b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1825 [inline]
 #2: ffff888025da6b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_ext_migrate+0x3bf/0x2000 fs/ext4/migrate.c:438

stack backtrace:
CPU: 1 UID: 0 PID: 9383 Comm: syz.2.893 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 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 kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs/super.h:19 [inline]
 sb_start_intwrite include/linux/fs/super.h:177 [inline]
 ext4_evict_inode+0xd3c/0x17c0 fs/ext4/inode.c:216
 evict+0x3c2/0xad0 fs/inode.c:846
 iput_final fs/inode.c:1966 [inline]
 iput.part.0+0x605/0xf50 fs/inode.c:2015
 iput+0x35/0x40 fs/inode.c:1981
 ext4_ext_migrate+0xd61/0x2000 fs/ext4/migrate.c:594
 __ext4_ioctl+0xd7e/0x42a0 fs/ext4/ioctl.c:1693
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f499bb9c629
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:00007f499ca5e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f499be16090 RCX: 00007f499bb9c629
RDX: 0000000000000000 RSI: 0000000000006609 RDI: 0000000000000008
RBP: 00007f499bc32b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f499be16128 R14: 00007f499be16090 R15: 00007ffc501a69c8
 </TASK>