[Patch net] net_sched: check noop_qdisc before qdisc_hash_add()

[Patch net] net_sched: check noop_qdisc before qdisc_hash_add()

[Cong Wang]

Dmitry reported a crash when injecting faults in
attach_one_default_qdisc() and dev->qdisc is still
a noop_disc, the check before qdisc_hash_add() fails
to catch it because it tests NULL. We should test
against noop_qdisc since it is the default qdisc
at this point.

Fixes: 59cc1f61f09c ("net: sched: convert qdisc linked list to hashtable")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 net/sched/sch_generic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index b052b27..1a2f9e9 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -794,7 +794,7 @@ static void attach_default_qdiscs(struct net_device *dev)
 		}
 	}
 #ifdef CONFIG_NET_SCHED
-	if (dev->qdisc)
+	if (dev->qdisc != &noop_qdisc)
 		qdisc_hash_add(dev->qdisc);
 #endif
 }
-- 
2.5.5

Re: [Patch net] net_sched: check noop_qdisc before qdisc_hash_add()

[Jiri Kosina]

On Tue, 4 Apr 2017, Cong Wang wrote:

> Dmitry reported a crash when injecting faults in
> attach_one_default_qdisc() and dev->qdisc is still
> a noop_disc, the check before qdisc_hash_add() fails
> to catch it because it tests NULL. We should test
> against noop_qdisc since it is the default qdisc
> at this point.
> 
> Fixes: 59cc1f61f09c ("net: sched: convert qdisc linked list to hashtable")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Jiri Kosina <jkosina@suse.cz>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Acked-by: Jiri Kosina <jkosina@suse.cz>

Thanks.

> ---
>  net/sched/sch_generic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index b052b27..1a2f9e9 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -794,7 +794,7 @@ static void attach_default_qdiscs(struct net_device *dev)
>  		}
>  	}
>  #ifdef CONFIG_NET_SCHED
> -	if (dev->qdisc)
> +	if (dev->qdisc != &noop_qdisc)
>  		qdisc_hash_add(dev->qdisc);
>  #endif
>  }
> -- 
> 2.5.5
> 

-- 
Jiri Kosina
SUSE Labs

Re: [Patch net] net_sched: check noop_qdisc before qdisc_hash_add()

[David Miller]

From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Tue,  4 Apr 2017 18:51:30 -0700

> Dmitry reported a crash when injecting faults in
> attach_one_default_qdisc() and dev->qdisc is still
> a noop_disc, the check before qdisc_hash_add() fails
> to catch it because it tests NULL. We should test
> against noop_qdisc since it is the default qdisc
> at this point.
> 
> Fixes: 59cc1f61f09c ("net: sched: convert qdisc linked list to hashtable")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Jiri Kosina <jkosina@suse.cz>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Applied and queued up for -stable.