[v5.15] possible deadlock in ext4_move_extents (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ac56c046adf4 Linux 5.15.195
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1029ac92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=5cbbe39beb13abc8459b
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/c11ec9487150/disk-ac56c046.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f1130a72d3a0/vmlinux-ac56c046.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7608cb6a3be5/bzImage-ac56c046.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5cbbe3...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.6.303/6091 is trying to acquire lock:
ffff8880730f1668 (&ei->i_data_sem/1){+.+.}-{3:3}, at: ext4_move_extents+0x31e/0xbd0 fs/ext4/move_extent.c:609

but task is already holding lock:
ffff8880730f0278 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40 fs/ext4/move_extent.c:-1

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ei->i_data_sem/2){++++}-{3:3}
:
down_write+0x38/0x60 kernel/locking/rwsem.c:1551
ext4_map_blocks+0x8b2/0x1b30 fs/ext4/inode.c:666
ext4_getblk+0x16d/0x630 fs/ext4/inode.c:870
ext4_bread+0x26/0x180 fs/ext4/inode.c:923
ext4_quota_write+0x230/0x570 fs/ext4/super.c:6596
write_blk fs/quota/quota_tree.c:64 [inline]
find_free_dqentry fs/quota/quota_tree.c:307 [inline]
do_insert_tree+0x115c/0x1970 fs/quota/quota_tree.c:364
do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
dq_insert_tree fs/quota/quota_tree.c:392 [inline]
qtree_write_dquot+0x361/0x4b0 fs/quota/quota_tree.c:411
v2_write_dquot+0x108/0x190 fs/quota/quota_v2.c:358
dquot_acquire+0x2d5/0x520 fs/quota/dquot.c:472
ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6205
dqget+0x778/0xeb0 fs/quota/dquot.c:988
__dquot_initialize+0x3b6/0xcb0 fs/quota/dquot.c:1517
ext4_process_orphan+0x54/0x300 fs/ext4/orphan.c:325
ext4_orphan_cleanup+0xaa9/0x12e0 fs/ext4/orphan.c:470
ext4_fill_super+0x92f0/0x9a60 fs/ext4/super.c:4975
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+0x2d6/0x3c0 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

-> #2 (&s->s_dquot.dqio_sem){++++}-{3:3}
:
down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
v2_read_dquot+0x4a/0x110 fs/quota/quota_v2.c:332
dquot_acquire+0x152/0x520 fs/quota/dquot.c:463
ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6205
dqget+0x778/0xeb0 fs/quota/dquot.c:988
__dquot_initialize+0x3b6/0xcb0 fs/quota/dquot.c:1517
ext4_file_open+0x2d1/0x6a0 fs/ext4/file.c:855
do_dentry_open+0x7ff/0xf80 fs/open.c:826
do_open fs/namei.c:3616 [inline]
path_openat+0x2682/0x2f30 fs/namei.c:3750
do_filp_open+0x1b3/0x3e0 fs/namei.c:3777
do_sys_openat2+0x142/0x4a0 fs/open.c:1253
do_sys_open fs/open.c:1269 [inline]
__do_sys_openat fs/open.c:1285 [inline]
__se_sys_openat fs/open.c:1280 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1280
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

-> #1 (&dquot->dq_lock){+.+.}-{3:3}:
__mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
dquot_commit+0x5a/0x410 fs/quota/dquot.c:507
ext4_write_dquot+0x1f0/0x360 fs/ext4/super.c:6185
mark_dquot_dirty fs/quota/dquot.c:372 [inline]
mark_all_dquot_dirty+0xf9/0x400 fs/quota/dquot.c:412
__dquot_free_space+0x7ca/0xb90 fs/quota/dquot.c:1942
dquot_free_space_nodirty include/linux/quotaops.h:376 [inline]
dquot_free_space+0x1b/0x30 include/linux/quotaops.h:381
swap_inode_boot_loader+0xc6a/0x10f0 fs/ext4/ioctl.c:241
__ext4_ioctl fs/ext4/ioctl.c:1056 [inline]
ext4_ioctl+0x18f3/0x3590 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

-> #0 (&ei->i_data_sem/1){+.+.}-{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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
down_write_nested+0x3b/0x60 kernel/locking/rwsem.c:1667
ext4_move_extents+0x31e/0xbd0 fs/ext4/move_extent.c:609
__ext4_ioctl fs/ext4/ioctl.c:990 [inline]
ext4_ioctl+0x2ce3/0x3590 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:

Chain exists of:
&ei->i_data_sem/1 --> &s->s_dquot.dqio_sem --> &ei->i_data_sem/2

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ei->i_data_sem/2);
lock(&s->s_dquot.dqio_sem);
lock(&ei->i_data_sem/2);
lock(&ei->i_data_sem/1);

*** DEADLOCK ***

4 locks held by syz.6.303/6091:
#0: ffff88807c61a460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
#1: ffff8880730f03f0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
#1: ffff8880730f03f0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: lock_two_nondirectories+0xd5/0x150 fs/inode.c:1147
#2: ffff8880730f17e0 (&sb->s_type->i_mutex_key#9/4){+.+.}-{3:3}, at: ext4_move_extents+0x303/0xbd0 fs/ext4/move_extent.c:602
#3: ffff8880730f0278 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40 fs/ext4/move_extent.c:-1

stack backtrace:
CPU: 1 PID: 6091 Comm: syz.6.303 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
check_noncircular+0x274/0x310 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+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
down_write_nested+0x3b/0x60 kernel/locking/rwsem.c:1667
ext4_move_extents+0x31e/0xbd0 fs/ext4/move_extent.c:609
__ext4_ioctl fs/ext4/ioctl.c:990 [inline]
ext4_ioctl+0x2ce3/0x3590 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: 0033:0x7f11f4a19fc9
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:00007f11f2c81038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f11f4c70fa0 RCX: 00007f11f4a19fc9
RDX: 0000200000000080 RSI: 00000000c028660f RDI: 0000000000000005
RBP: 00007f11f4a9cf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f11f4c71038 R14: 00007f11f4c70fa0 R15: 00007fff9ae09fb8
</TASK>


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