[v6.6] WARNING in free_conf

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 79643295eba1 Linux 6.6.157
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1764b915580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7be9809cedd6b69c
dashboard link: https://syzkaller.appspot.com/bug?extid=54132eadfe0879fb7554
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14e4b915580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17400005580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a1af8d16581c/disk-79643295.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/66be9bddb1ec/vmlinux-79643295.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0329b316645d/bzImage-79643295.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+54132e...@syzkaller.appspotmail.com

Object 0xffff88805b96d838 @offset=6200
Object 0xffff88805b96dd10 @offset=7440
Object 0xffff88805b96e1e8 @offset=8680
Object 0xffff88805b96e6c0 @offset=9920
------------[ cut here ]------------
kmem_cache_destroy raid5-md0: Slab cache still has objects when called from shrink_stripes drivers/md/raid5.c:2726 [inline]
kmem_cache_destroy raid5-md0: Slab cache still has objects when called from free_conf+0x227/0x4b0 drivers/md/raid5.c:7442
WARNING: CPU: 1 PID: 6111 at mm/slab_common.c:499 kmem_cache_destroy+0x74/0x160 mm/slab_common.c:498
Modules linked in:
CPU: 1 PID: 6111 Comm: syz.2.33 Tainted: G B syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:kmem_cache_destroy+0x74/0x160 mm/slab_common.c:498
Code: 52 9d 1a 00 48 89 df e8 ea f3 19 00 85 c0 74 33 48 8b 53 60 48 c7 c7 84 49 89 8c 48 c7 c6 31 71 a6 8c 4c 89 f1 e8 7c e5 8b ff <0f> 0b 48 c7 c7 f0 0a 20 8d e8 5e 83 d4 08 5b 41 5e 41 5f 5d e9 63
RSP: 0018:ffffc90003947930 EFLAGS: 00010246
RAX: 32346eef81984600 RBX: ffff88806bd7a780 RCX: ffff888079e93c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: 0000000048000000 R08: ffffc90003947527 R09: 1ffff92000728ea4
R10: dffffc0000000000 R11: fffff52000728ea5 R12: ffff888026d96000
R13: dffffc0000000000 R14: ffffffff8777c207 R15: 0000000000000000
FS: 00007f51ca9bb6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000292f0a9d4000 CR3: 0000000061a20000 CR4: 00000000003506e0
Call Trace:
<TASK>
shrink_stripes drivers/md/raid5.c:2726 [inline]
free_conf+0x227/0x4b0 drivers/md/raid5.c:7442
setup_conf+0x16c4/0x2a30 drivers/md/raid5.c:7772
raid5_takeover_raid1 drivers/md/raid5.c:8825 [inline]
raid5_takeover+0x61d/0x8a0 drivers/md/raid5.c:8936
level_store+0x6b1/0x1a90 drivers/md/md.c:4028
md_attr_store+0x196/0x380 drivers/md/md.c:5637
kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x474/0x9a0 fs/read_write.c:584
ksys_write+0x151/0x260 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f51c9b9e159
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:00007f51ca9bb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f51c9e26180 RCX: 00007f51c9b9e159
RDX: 0000000000000005 RSI: 0000200000000300 RDI: 0000000000000007
RBP: 00007f51c9c3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f51c9e26218 R14: 00007f51c9e26180 R15: 00007ffeee866e38
</TASK>


---
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