netlink: make sure nladdr has correct size in netlink_connect()

commit 7880287981b60a6808f39f297bb66936e8bdf57a upstream.

KMSAN reports use of uninitialized memory in the case when |alen| is
smaller than sizeof(struct sockaddr_nl), and therefore |nladdr| isn't
fully copied from the userspace.

Signed-off-by: Alexander Potapenko <glider@google.com>
Fixes: 1da177e4c3f41524 ("Linux-2.6.12-rc2")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 2369e96..d1017ad 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -706,6 +706,9 @@ static int netlink_connect(struct socket *sock, struct sockaddr *addr,
        if (addr->sa_family != AF_NETLINK)
                return -EINVAL;
 
+       if (alen < sizeof(struct sockaddr_nl))
+               return -EINVAL;
+
        /* Only superuser is allowed to send multicasts */
        if (nladdr->nl_groups && !netlink_capable(sock, NL_NONROOT_SEND))
                return -EPERM;