[PATCH net] packet: fix heap info leak in PACKET_DIAG_MCLIST sock_diag interface

[Mathias Krause <minipli@googlemail.com>]

Because we miss to wipe the remainder of i->addr[] in packet_mc_add(),
pdiag_put_mclist() leaks uninitialized heap bytes via the
PACKET_DIAG_MCLIST netlink attribute.

Fix this by explicitly memset(0)ing the remaining bytes in i->addr[].

Fixes: eea68e2f1a00 ("packet: Report socket mclist info via diag module")
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
---
The bug itself precedes commit eea68e2f1a00 but the list wasn't exposed
to userland before the introduction of the packet_diag interface.
Therefore the "Fixes:" line on that commit.

 net/packet/af_packet.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 992396aa635c..86a408cf38d5 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3441,6 +3441,7 @@ static int packet_mc_add(struct sock *sk, struct packet_mreq_max *mreq)
 	i->ifindex = mreq->mr_ifindex;
 	i->alen = mreq->mr_alen;
 	memcpy(i->addr, mreq->mr_address, i->alen);
+	memset(i->addr + i->alen, 0, sizeof(i->addr) - i->alen);
 	i->count = 1;
 	i->next = po->mclist;
 	po->mclist = i;
-- 
1.7.10.4