* [PATCH v2] net: sched: Fix a possible null-pointer dereference in dequeue_func()
@ 2019-07-29 8:00 Jia-Ju Bai
2019-07-29 8:18 ` Jiri Pirko
0 siblings, 1 reply; 3+ messages in thread
From: Jia-Ju Bai @ 2019-07-29 8:00 UTC (permalink / raw)
To: jhs, xiyou.wangcong, jiri, davem; +Cc: netdev, linux-kernel, Jia-Ju Bai
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")
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
v2:
* Add a fix tag.
Thank Jiri Pirko for helpful advice.
---
net/sched/sch_codel.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index 25ef172c23df..30169b3adbbb 100644
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -71,10 +71,10 @@ static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
struct Qdisc *sch = ctx;
struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
- if (skb)
+ if (skb) {
sch->qstats.backlog -= qdisc_pkt_len(skb);
-
- prefetch(&skb->end); /* we'll need skb_shinfo() */
+ prefetch(&skb->end); /* we'll need skb_shinfo() */
+ }
return skb;
}
--
2.17.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] net: sched: Fix a possible null-pointer dereference in dequeue_func()
2019-07-29 8:00 [PATCH v2] net: sched: Fix a possible null-pointer dereference in dequeue_func() Jia-Ju Bai
@ 2019-07-29 8:18 ` Jiri Pirko
2019-07-29 8:25 ` Jia-Ju Bai
0 siblings, 1 reply; 3+ messages in thread
From: Jiri Pirko @ 2019-07-29 8:18 UTC (permalink / raw)
To: Jia-Ju Bai; +Cc: jhs, xiyou.wangcong, davem, netdev, linux-kernel
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:".
The fix itself looks fine to me.
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
>Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>---
>v2:
>* Add a fix tag.
> Thank Jiri Pirko for helpful advice.
>
>---
> net/sched/sch_codel.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
>index 25ef172c23df..30169b3adbbb 100644
>--- a/net/sched/sch_codel.c
>+++ b/net/sched/sch_codel.c
>@@ -71,10 +71,10 @@ static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
> struct Qdisc *sch = ctx;
> struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);
>
>- if (skb)
>+ if (skb) {
> sch->qstats.backlog -= qdisc_pkt_len(skb);
>-
>- prefetch(&skb->end); /* we'll need skb_shinfo() */
>+ prefetch(&skb->end); /* we'll need skb_shinfo() */
>+ }
> return skb;
> }
>
>--
>2.17.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] net: sched: Fix a possible null-pointer dereference in dequeue_func()
2019-07-29 8:18 ` Jiri Pirko
@ 2019-07-29 8:25 ` Jia-Ju Bai
0 siblings, 0 replies; 3+ messages in thread
From: Jia-Ju Bai @ 2019-07-29 8:25 UTC (permalink / raw)
To: Jiri Pirko; +Cc: jhs, xiyou.wangcong, davem, netdev, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-07-29 8:18 ` Jiri Pirko
2019-07-29 8:25 ` Jia-Ju Bai
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