[PATCH] bridge: don't try to update timers in case of broken MLD queries

[PATCH] bridge: don't try to update timers in case of broken MLD queries

[Linus Lüssing]

Currently we are reading an uninitialized value for the max_delay
variable when snooping an MLD query message of invalid length and would
update our timers with that.

Fixing this by simply ignoring such broken MLD queries (just like we do
for IGMP already).

This is a regression introduced by:
"bridge: disable snooping if there is no querier" (b00589af3b04)

Reported-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Linus Lüssing <linus.luessing@web.de>
---
 net/bridge/br_multicast.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 61c5e81..08e576a 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -1195,7 +1195,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
 		max_delay = msecs_to_jiffies(ntohs(mld->mld_maxdelay));
 		if (max_delay)
 			group = &mld->mld_mca;
-	} else if (skb->len >= sizeof(*mld2q)) {
+	} else {
 		if (!pskb_may_pull(skb, sizeof(*mld2q))) {
 			err = -EINVAL;
 			goto out;
-- 
1.7.10.4

Re: [PATCH] bridge: don't try to update timers in case of broken MLD queries

[Stephen Hemminger]

On Tue,  6 Aug 2013 00:32:05 +0200
Linus Lüssing <linus.luessing@web.de> wrote:

> Currently we are reading an uninitialized value for the max_delay
> variable when snooping an MLD query message of invalid length and would
> update our timers with that.
> 
> Fixing this by simply ignoring such broken MLD queries (just like we do
> for IGMP already).
> 
> This is a regression introduced by:
> "bridge: disable snooping if there is no querier" (b00589af3b04)
> 
> Reported-by: Paul Bolle <pebolle@tiscali.nl>
> Signed-off-by: Linus Lüssing <linus.luessing@web.de>
> ---
>  net/bridge/br_multicast.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index 61c5e81..08e576a 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1195,7 +1195,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
>  		max_delay = msecs_to_jiffies(ntohs(mld->mld_maxdelay));
>  		if (max_delay)
>  			group = &mld->mld_mca;
> -	} else if (skb->len >= sizeof(*mld2q)) {
> +	} else {
>  		if (!pskb_may_pull(skb, sizeof(*mld2q))) {
>  			err = -EINVAL;
>  			goto out;

Why not use else if here, other than that looks great.

Re: [PATCH] bridge: don't try to update timers in case of broken MLD queries

[David Miller]

From: Linus Lüssing <linus.luessing@web.de>
Date: Tue,  6 Aug 2013 00:32:05 +0200

> Currently we are reading an uninitialized value for the max_delay
> variable when snooping an MLD query message of invalid length and would
> update our timers with that.
> 
> Fixing this by simply ignoring such broken MLD queries (just like we do
> for IGMP already).
> 
> This is a regression introduced by:
> "bridge: disable snooping if there is no querier" (b00589af3b04)
> 
> Reported-by: Paul Bolle <pebolle@tiscali.nl>
> Signed-off-by: Linus Lüssing <linus.luessing@web.de>

Applied, thanks.

Re: [PATCH] bridge: don't try to update timers in case of broken MLD queries

[Linus Lüssing]

On Mon, Aug 05, 2013 at 03:42:22PM -0700, Stephen Hemminger wrote:
> On Tue,  6 Aug 2013 00:32:05 +0200
> Linus Lüssing <linus.luessing@web.de> wrote:
> 
> > Currently we are reading an uninitialized value for the max_delay
> > variable when snooping an MLD query message of invalid length and would
> > update our timers with that.
> > 
> > Fixing this by simply ignoring such broken MLD queries (just like we do
> > for IGMP already).
> > 
> > This is a regression introduced by:
> > "bridge: disable snooping if there is no querier" (b00589af3b04)
> > 
> > Reported-by: Paul Bolle <pebolle@tiscali.nl>
> > Signed-off-by: Linus Lüssing <linus.luessing@web.de>
> > ---
> >  net/bridge/br_multicast.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> > index 61c5e81..08e576a 100644
> > --- a/net/bridge/br_multicast.c
> > +++ b/net/bridge/br_multicast.c
> > @@ -1195,7 +1195,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
> >  		max_delay = msecs_to_jiffies(ntohs(mld->mld_maxdelay));
> >  		if (max_delay)
> >  			group = &mld->mld_mca;
> > -	} else if (skb->len >= sizeof(*mld2q)) {
> > +	} else {
> >  		if (!pskb_may_pull(skb, sizeof(*mld2q))) {
> >  			err = -EINVAL;
> >  			goto out;
> 
> Why not use else if here, other than that looks great.

Because it isn't really necessary, it is basically included
in the pskb_may_pull() already, just like it is in the according IGMP
code path.

And I thought it'd be nicer to handle it the same way as in the
IGMP code path to avoid diverging too much.

Cheers, Linus