linux-kernel - Re: [syzbot] [cgroups?] WARNING in css_rstat

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Message-ID: <fd40f2db-66e2-4bc1-9a16-4a301d807a88@gmail.com>
Date: Mon, 16 Jun 2025 21:46:52 -0700
From: JP Kobryn <inwardvessel@...il.com>
To: Michal Koutný <mkoutny@...e.com>,
 syzbot <syzbot+8d052e8b99e40bc625ed@...kaller.appspotmail.com>
Cc: cgroups@...r.kernel.org, hannes@...xchg.org,
 linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, tj@...nel.org
Subject: Re: [syzbot] [cgroups?] WARNING in css_rstat_exit

On 6/16/25 2:49 AM, Michal Koutný wrote:
> +Cc: JP

Thanks. Looking into this.

> 
> On Fri, Jun 13, 2025 at 09:55:30AM -0700, syzbot <syzbot+8d052e8b99e40bc625ed@...kaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    27605c8c0f69 Merge tag 'net-6.16-rc2' of git://git.kernel...
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=103b1e0c580000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=89df02a4e09cb64d
>> dashboard link: https://syzkaller.appspot.com/bug?extid=8d052e8b99e40bc625ed
>> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/79ab1e186123/disk-27605c8c.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/d37bf85b966d/vmlinux-27605c8c.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/eed2865abf8f/bzImage-27605c8c.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+8d052e8b99e40bc625ed@...kaller.appspotmail.com
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 5887 at kernel/cgroup/rstat.c:497 css_rstat_exit+0x368/0x470 kernel/cgroup/rstat.c:497
>> Modules linked in:
>> CPU: 0 UID: 0 PID: 5887 Comm: kworker/0:5 Not tainted 6.16.0-rc1-syzkaller-00101-g27605c8c0f69 #0 PREEMPT(full)
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
>> Workqueue: cgroup_destroy css_free_rwork_fn
>> RIP: 0010:css_rstat_exit+0x368/0x470 kernel/cgroup/rstat.c:497
>> Code: 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 0e 01 00 00 49 c7 85 70 05 00 00 00 00 00 00 e9 00 ff ff ff e8 c9 07 07 00 90 <0f> 0b 90 e9 3e ff ff ff e8 bb 07 07 00 90 0f 0b 90 e9 30 ff ff ff
>> RSP: 0000:ffffc9000b6afbc0 EFLAGS: 00010293
>> RAX: 0000000000000000 RBX: ffff888057c7a800 RCX: ffff888124754000
>> RDX: ffff8880308b8000 RSI: ffffffff81b514e7 RDI: ffffffff8df26da0
>> RBP: ffff888057c7a808 R08: 0000000000000005 R09: 0000000000000007
>> R10: 0000000000000000 R11: 0000000000000001 R12: ffff888057c7a820
>> R13: 0000000000000000 R14: 0000000000000003 R15: dffffc0000000000
>> FS:  0000000000000000(0000) GS:ffff888124754000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000001b31b10ff8 CR3: 0000000079092000 CR4: 00000000003526f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>   <TASK>
>>   css_free_rwork_fn+0x80/0x12e0 kernel/cgroup/cgroup.c:5449
>>   process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
>>   process_scheduled_works kernel/workqueue.c:3321 [inline]
>>   worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
>>   kthread+0x3c5/0x780 kernel/kthread.c:464
>>   ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
>>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>>   </TASK>
>>
>>
>> ---
>> This report is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@...glegroups.com.
>>
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>
>> If the report is already addressed, let syzbot know by replying with:
>> #syz fix: exact-commit-title
>>
>> If you want to overwrite report's subsystems, reply with:
>> #syz set subsystems: new-subsystem
>> (See the list of subsystem names on the web dashboard)
>>
>> If the report is a duplicate of another one, reply with:
>> #syz dup: exact-subject-of-another-report
>>
>> If you want to undo deduplication, reply with:
>> #syz undup