[syzbot] [cgroups?] WARNING in cgroup_freeze

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 50c19e20ed2e Merge tag 'nolibc-20250928-for-6.18-1' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=137446e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=cfc4e6ee70d55834
dashboard link: https://syzkaller.appspot.com/bug?extid=27a2519eb4dad86d0156
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11eba42c580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15de5d04580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/10a80b79b188/disk-50c19e20.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e782595cfe10/vmlinux-50c19e20.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9166ef44f6be/bzImage-50c19e20.xz

The issue was bisected to:

commit afa3701c0e45ecb9e4d160048ca4e353c7489948
Author: Tiffany Yang <yna...@google.com>
Date: Fri Aug 22 01:37:52 2025 +0000

cgroup: cgroup.stat.local time accounting

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12c22092580000
final oops: https://syzkaller.appspot.com/x/report.txt?x=11c22092580000
console output: https://syzkaller.appspot.com/x/log.txt?x=16c22092580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+27a251...@syzkaller.appspotmail.com
Fixes: afa3701c0e45 ("cgroup: cgroup.stat.local time accounting")

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6062 at ./include/linux/seqlock.h:221 __seqprop_assert include/linux/seqlock.h:221 [inline]
WARNING: CPU: 0 PID: 6062 at ./include/linux/seqlock.h:221 cgroup_do_freeze kernel/cgroup/freezer.c:182 [inline]
WARNING: CPU: 0 PID: 6062 at ./include/linux/seqlock.h:221 cgroup_freeze+0x80a/0xf90 kernel/cgroup/freezer.c:309
Modules linked in:
CPU: 0 UID: 0 PID: 6062 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__seqprop_assert include/linux/seqlock.h:221 [inline]
RIP: 0010:cgroup_do_freeze kernel/cgroup/freezer.c:182 [inline]
RIP: 0010:cgroup_freeze+0x80a/0xf90 kernel/cgroup/freezer.c:309
Code: 90 e9 9e fb ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c e7 f9 ff ff 4c 89 f7 e8 e1 43 67 00 e9 da f9 ff ff e8 17 68 06 00 90 <0f> 0b 90 e9 10 fc ff ff 44 89 f9 80 e1 07 38 c1 48 8b 0c 24 0f 8c
RSP: 0018:ffffc90003e7f8e0 EFLAGS: 00010293
RAX: ffffffff81b6c6a9 RBX: 0000000000000000 RCX: ffff88802ff60000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003e7fa70 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1d6d2a7 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000001 R15: ffff888031790791
FS: 0000555589dcd500(0000) GS:ffff888127017000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f163fff CR3: 000000002f824000 CR4: 00000000003526f0
Call Trace:
<TASK>
cgroup_freeze_write+0x156/0x1c0 kernel/cgroup/cgroup.c:4174
cgroup_file_write+0x39b/0x740 kernel/cgroup/cgroup.c:4312
kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5d5/0xb40 fs/read_write.c:686
ksys_write+0x14b/0x260 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f717e32eec9
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:00007ffe6a7c7c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f717e585fa0 RCX: 00007f717e32eec9
RDX: 0000000000000012 RSI: 0000200000000200 RDI: 0000000000000004
RBP: 00007f717e3b1f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f717e585fa0 R14: 00007f717e585fa0 R15: 0000000000000003
</TASK>


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