Re: [PATCH v2] net: sched: Fix a possible null-pointer dereference in dequeue_func()

[Jia-Ju Bai]

On 2019/7/29 16:18, Jiri Pirko wrote:

Mon, Jul 29, 2019 at 10:00:18AM CEST, baijiaju1...@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 <eduma...@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