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Message-ID: <177cc1f5-3b11-cde1-5769-f18e87890083@redhat.com>
Date:   Mon, 5 Jun 2023 10:51:50 -0400
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Subject: Re: [PATCH] cgroup: fixed the cset refcnt leak when fork() failed
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From:   Waiman Long <longman@redhat.com>
To:     Zou Cao <zoucaox@gmail.com>, linux-kernel@vger.kernel.org,
        tj@kernel.org
Cc:     cgroups@vger.kernel.org, lizefan.x@bytedance.com,
        hannes@cmpxchg.org, brauner@kernel.org,
        Zou Cao <zoucao@kuaishou.com>
References: <20230605130444.1421-1-zoucao@kuaishou.com>
 <e0d1998f-c081-30e6-7646-cf6460c2d67c@redhat.com>
In-Reply-To: <e0d1998f-c081-30e6-7646-cf6460c2d67c@redhat.com>
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On 6/5/23 10:12, Waiman Long wrote:
>> kernel/cgroup/cgroup.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
>> index d18c2ef..5ecd706 100644
>> --- a/kernel/cgroup/cgroup.c
>> +++ b/kernel/cgroup/cgroup.c
>> @@ -6284,6 +6284,11 @@ void cgroup_cancel_fork(struct task_struct 
>> *child,
>>           if (ss->cancel_fork)
>>               ss->cancel_fork(child, kargs->cset);
>>   +    if (!(kargs->flags & CLONE_INTO_CGROUP) &&
>> +            kargs->cset) {
>> +        put_css_set(kargs->cset);
>> +    }
>> +
> I believe the out_revert error path of cgroup_can_fork() has a similar 
> issue. Perhaps you may want to put the put_css_set() call in 
> cgroup_css_set_put_fork().

Sorry, it should not be done in cgroup_css_set_put_fork(). As the 
increase in reference is properly matched in css_post_fork(). That means 
similar change will be needed in cgroup_can_fork().

Cheers,
Longman