bridge br_multicast: BUG: unable to handle kernel NULL pointer dereference

bridge br_multicast: BUG: unable to handle kernel NULL pointer dereference

On Tue, Jul 06, 2010 at 08:48:35AM +0800, Herbert Xu wrote:
>
> bridge: Restore NULL check in br_mdb_ip_get

Resend with proper attribution.

bridge: Restore NULL check in br_mdb_ip_get

Somewhere along the line the NULL check in br_mdb_ip_get went
AWOL, causing crashes when we receive an IGMP packet with no
multicast table allocated.

This patch restores it and ensures all br_mdb_*_get functions
use it.

Reported-by: Frank Arnold <frank.arnold@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Thanks,
Signed-off-by: David S. Miller <davem@davemloft.net>