[syzbot] [gfs2?] WARNING in gfs2_fill_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 09c0f7f1bcdb Add linux-next specific files for 20260323
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=142ade02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0c30527ccbcb0f2
dashboard link: https://syzkaller.appspot.com/bug?extid=b441db1854c360b83221
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=145e16da580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b33b52580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c320a7a1bc69/disk-09c0f7f1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4a5b231960d2/vmlinux-09c0f7f1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8e2b84b9674d/bzImage-09c0f7f1.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/a4941369e2d2/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=170daa06580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b441db...@syzkaller.appspotmail.com

loop4: detected capacity change from 0 to 32768
------------[ cut here ]------------
kmem_cache of name 'gfs2-bufdata/syz:syz' already exists
WARNING: mm/slab_common.c:112 at kmem_cache_sanity_check mm/slab_common.c:111 [inline], CPU#1: syz.4.21/6090
WARNING: mm/slab_common.c:112 at __kmem_cache_create_args+0xac/0x440 mm/slab_common.c:352, CPU#1: syz.4.21/6090
Modules linked in:
CPU: 1 UID: 0 PID: 6090 Comm: syz.4.21 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:kmem_cache_sanity_check mm/slab_common.c:111 [inline]
RIP: 0010:__kmem_cache_create_args+0xaf/0x440 mm/slab_common.c:352
Code: 86 8e 4d 8b 24 24 49 81 fc 18 68 86 8e 74 20 49 8b 7c 24 f8 48 89 de e8 3f 5c 9c 09 85 c0 75 e2 48 8d 3d 54 70 06 0e 48 89 de <67> 48 0f b9 3a 48 89 df be 20 00 00 00 e8 df 5d 9c 09 48 85 c0 0f
RSP: 0018:ffffc900025f7948 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88807ac1dac0 RCX: 0000000000000005
RDX: 000000007ac1da04 RSI: ffff88807ac1dac0 RDI: ffffffff9016e0b0
RBP: 0000000000000000 R08: ffffffff901246f7 R09: 1ffffffff20248de
R10: dffffc0000000000 R11: fffffbfff20248df R12: ffff8881442f37e0
R13: ffff88807caa0000 R14: 0000000000000050 R15: ffffc900025f7a60
FS: 000055555c597500(0000) GS:ffff888125548000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fefd604b544 CR3: 0000000035aa2000 CR4: 00000000003526f0
Call Trace:
<TASK>
__kmem_cache_create include/linux/slab.h:390 [inline]
gfs2_fill_super+0x13a4/0x21d0 fs/gfs2/ops_fstype.c:1202
get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1342
vfs_get_tree+0x92/0x2a0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3764 [inline]
do_new_mount+0x341/0xd30 fs/namespace.c:3840
do_mount fs/namespace.c:4173 [inline]
__do_sys_mount fs/namespace.c:4372 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4349
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fefd5f9da0a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fff558aaf78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff558ab000 RCX: 00007fefd5f9da0a
RDX: 00002000000124c0 RSI: 0000200000012500 RDI: 00007fff558aafc0
RBP: 00002000000124c0 R08: 00007fff558ab000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000012500
R13: 00007fff558aafc0 R14: 00000000000125c7 R15: 0000200000000180
</TASK>
----------------
Code disassembly (best guess):
0: 86 8e 4d 8b 24 24 xchg %cl,0x24248b4d(%rsi)
6: 49 81 fc 18 68 86 8e cmp $0xffffffff8e866818,%r12
d: 74 20 je 0x2f
f: 49 8b 7c 24 f8 mov -0x8(%r12),%rdi
14: 48 89 de mov %rbx,%rsi
17: e8 3f 5c 9c 09 call 0x99c5c5b
1c: 85 c0 test %eax,%eax
1e: 75 e2 jne 0x2
20: 48 8d 3d 54 70 06 0e lea 0xe067054(%rip),%rdi # 0xe06707b
27: 48 89 de mov %rbx,%rsi
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 48 89 df mov %rbx,%rdi
32: be 20 00 00 00 mov $0x20,%esi
37: e8 df 5d 9c 09 call 0x99c5e1b
3c: 48 85 c0 test %rax,%rax
3f: 0f .byte 0xf


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