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SubjectRe: [PATCH] net: sched: fix potential null pointer deref
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Hi Jianhao,

On 6/10/22 4:14 AM, Jianhao Xu wrote:
> mq_queue_get() may return NULL, a check is needed to avoid using
> the NULL pointer.
>
> Signed-off-by: Jianhao Xu <jianhao_xu@smail.nju.edu.cn>

Do you have a reproducer where this is triggered?

> ---
> net/sched/sch_mq.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/net/sched/sch_mq.c b/net/sched/sch_mq.c
> index 83d2e54bf303..9aca4ca82947 100644
> --- a/net/sched/sch_mq.c
> +++ b/net/sched/sch_mq.c
> @@ -201,6 +201,8 @@ static int mq_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
> static struct Qdisc *mq_leaf(struct Qdisc *sch, unsigned long cl)
> {
> struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
> + if (!dev_queue)
> + return NULL;
>
> return dev_queue->qdisc_sleeping;
> }
> @@ -218,6 +220,8 @@ static int mq_dump_class(struct Qdisc *sch, unsigned long cl,
> struct sk_buff *skb, struct tcmsg *tcm)
> {
> struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
> + if (!dev_queue)
> + return -1;
>
> tcm->tcm_parent = TC_H_ROOT;
> tcm->tcm_handle |= TC_H_MIN(cl);
> @@ -229,6 +233,8 @@ static int mq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
> struct gnet_dump *d)
> {
> struct netdev_queue *dev_queue = mq_queue_get(sch, cl);
> + if (!dev_queue)
> + return -1;
>
> sch = dev_queue->qdisc_sleeping;
> if (gnet_stats_copy_basic(d, sch->cpu_bstats, &sch->bstats, true) < 0 ||
>

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