[syzbot] [ext4?] WARNING: locking bug in ext4_xattr_inode_update_ref (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f2f80ac80987 Merge tag 'nfsd-6.9-2' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1734efc5180000
kernel config: https://syzkaller.appspot.com/x/.config?x=411644804960f423
dashboard link: https://syzkaller.appspot.com/bug?extid=3ca210b2c10e57015b3c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11e7f79d180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1614c105180000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-f2f80ac8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/226f497bcbfb/vmlinux-f2f80ac8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6cae4ca2cad5/bzImage-f2f80ac8.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2780392925e4/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3ca210...@syzkaller.appspotmail.com

------------[ cut here ]------------
Looking for class "&ea_inode->i_rwsem" with key ext4_fs_type, but found a different class "&sb->s_type->i_mutex_key" with the same key
WARNING: CPU: 0 PID: 5434 at kernel/locking/lockdep.c:932 look_up_lock_class+0x133/0x140 kernel/locking/lockdep.c:932
Modules linked in:
CPU: 0 PID: 5434 Comm: syz-executor760 Not tainted 6.9.0-rc2-syzkaller-00413-gf2f80ac80987 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:look_up_lock_class+0x133/0x140 kernel/locking/lockdep.c:932
Code: c7 c7 20 ca 2c 8b e8 dc 76 70 f6 90 0f 0b 90 90 90 31 db eb be c6 05 02 67 eb 04 01 90 48 c7 c7 40 cd 2c 8b e8 be 76 70 f6 90 <0f> 0b 90 90 e9 62 ff ff ff 0f 1f 40 00 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90003ef6ea0 EFLAGS: 00010082
RAX: 0000000000000000 RBX: ffffffff942543e8 RCX: ffffffff814fe349
RDX: ffff8880259da440 RSI: ffffffff814fe356 RDI: 0000000000000001
RBP: ffffffff8de72ed8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 000000006b6f6f4c R12: ffff8880329db600
R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff94af1aa0
FS: 00007fb2680336c0(0000) GS:ffff88806b000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555582e00778 CR3: 0000000019d34000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
register_lock_class+0xb1/0x1230 kernel/locking/lockdep.c:1284
__lock_acquire+0x111/0x3b30 kernel/locking/lockdep.c:5014
lock_acquire kernel/locking/lockdep.c:5754 [inline]
lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
down_write+0x3a/0x50 kernel/locking/rwsem.c:1579
inode_lock include/linux/fs.h:795 [inline]
ext4_xattr_inode_update_ref+0xa6/0x5e0 fs/ext4/xattr.c:1042
ext4_xattr_inode_inc_ref fs/ext4/xattr.c:1088 [inline]
ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1583 [inline]
ext4_xattr_set_entry+0x125f/0x3c70 fs/ext4/xattr.c:1718
ext4_xattr_block_set+0xcc3/0x3100 fs/ext4/xattr.c:2037
ext4_xattr_set_handle+0xdb6/0x1480 fs/ext4/xattr.c:2443
ext4_xattr_set+0x149/0x380 fs/ext4/xattr.c:2545
__vfs_setxattr+0x173/0x1e0 fs/xattr.c:200
__vfs_setxattr_noperm+0x127/0x5e0 fs/xattr.c:234
__vfs_setxattr_locked+0x182/0x260 fs/xattr.c:295
vfs_setxattr+0x146/0x350 fs/xattr.c:321
do_setxattr+0x146/0x170 fs/xattr.c:629
setxattr+0x15d/0x180 fs/xattr.c:652
path_setxattr+0x179/0x1e0 fs/xattr.c:671
__do_sys_setxattr fs/xattr.c:687 [inline]
__se_sys_setxattr fs/xattr.c:683 [inline]
__x64_sys_setxattr+0xc4/0x160 fs/xattr.c:683
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x72/0x7a
RIP: 0033:0x7fb26807cf79
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb268033218 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fb26807cf79
RDX: 00000000200005c0 RSI: 0000000020000180 RDI: 0000000020000080
RBP: 00007fb2681056a8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000002000 R11: 0000000000000246 R12: 00007fb2681056a0
R13: 0072657070752e79 R14: 0030656c69662f2e R15: 2f30656c69662f2e
</TASK>


---
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[Hillf Danton]

On Thu, 11 Apr 2024 02:48:27 -0700

> syzbot found the following issue on:
>
> HEAD commit: f2f80ac80987 Merge tag 'nfsd-6.9-2' of git://git.kernel.or..
> git tree: upstream

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1614c105180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f2f80ac80987

--- x/fs/ext4/xattr.c
+++ y/fs/ext4/xattr.c
@@ -119,11 +119,12 @@ ext4_expand_inode_array(struct ext4_xatt
struct inode *inode);

#ifdef CONFIG_LOCKDEP
+static struct lock_class_key ea_i_rwsem_key;
void ext4_xattr_inode_set_class(struct inode *ea_inode)
{
struct ext4_inode_info *ei = EXT4_I(ea_inode);

- lockdep_set_subclass(&ea_inode->i_rwsem, 1);
+ lockdep_set_class(&ea_inode->i_rwsem, &ea_i_rwsem_key);
(void) ei; /* shut up clang warning if !CONFIG_LOCKDEP */
lockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_EA);
}
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+3ca210...@syzkaller.appspotmail.com

Tested on:

commit: f2f80ac8 Merge tag 'nfsd-6.9-2' of git://git.kernel.or..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=17315a47180000

kernel config: https://syzkaller.appspot.com/x/.config?x=411644804960f423
dashboard link: https://syzkaller.appspot.com/bug?extid=3ca210b2c10e57015b3c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=12a085cb180000

Note: testing is done by a robot and is best-effort only.