linux-kernel - Re: [PATCH] net: sched: Fix a possible null-pointer dereference in dequeue

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Message-ID: <5a8fc4cb-4ee8-b2be-2b14-90e8285fef07@gmail.com>
Date:   Mon, 29 Jul 2019 15:59:10 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: sched: Fix a possible null-pointer dereference in
 dequeue_func()



On 2019/7/29 15:41, Jiri Pirko wrote:
> Mon, Jul 29, 2019 at 09:32:00AM CEST, baijiaju1990@...il.com wrote:
>>
>> On 2019/7/29 14:56, Jiri Pirko wrote:
>>> Mon, Jul 29, 2019 at 04:21:57AM CEST, baijiaju1990@...il.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.
>>>>
>>>> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
>>> Fixes tag, please?
>> Sorry, I do not know what "fixes tag" means...
>> I just find a possible bug and fix it in this patch.
> git log |grep Fixes:
>
> If A fix goes to -net tree, it most probably fixes some bug introduced
> by some commit in the past. So this tag is to put a reference.

Thanks for the explanation.
I will add it and submit a v2 patch.


Best wishes,
Jia-Ju Bai