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Subject: Re: [PATCH v2] net: sched: Fix a possible null-pointer dereference in
 dequeue_func()
To:     Jiri Pirko <jiri@resnulli.us>
Cc:     jhs@mojatatu.com, xiyou.wangcong@gmail.com, davem@davemloft.net,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190729080018.28678-1-baijiaju1990@gmail.com>
 <20190729081854.GC2211@nanopsycho>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <4619ec69-b800-1a61-7082-85ef4fa9af74@gmail.com>
Date:   Mon, 29 Jul 2019 16:25:41 +0800
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On 2019/7/29 16:18, Jiri Pirko wrote:
> Mon, Jul 29, 2019 at 10:00:18AM CEST, baijiaju1990@gmail.com wrote:
>> In dequeue_func(), there is an if statement on line 74 to check whether
>> skb is NULL:
>>     if (skb)
>>
>> When skb is NULL, it is used on line 77:
>>     prefetch(&skb->end);
>>
>> Thus, a possible null-pointer dereference may occur.
>>
>> To fix this bug, skb->end is used when skb is not NULL.
>>
>> This bug is found by a static analysis tool STCheck written by us.
>>
>> Fixes: 79bdc4c862af ("codel: generalize the implementation")
> Looks like this is something being there since the beginning:
> commit 76e3cc126bb223013a6b9a0e2a51238d1ef2e409
> Author: Eric Dumazet <edumazet@google.com>
> Date:   Thu May 10 07:51:25 2012 +0000
>
>      codel: Controlled Delay AQM
>
>
> Please adjust "Fixes:".

Thanks for the advice :)
I have sent a v3 patch.


Best wishes,
Jia-Ju Bai