packet: packet_getname_spkt: make sure string is always 0-terminated

[ Upstream commit 2dc85bf323515e59e15dfa858d1472bb25cad0fe ]

uaddr->sa_data is exactly of size 14, which is hard-coded here and
passed as a size argument to strncpy(). A device name can be of size
IFNAMSIZ (== 16), meaning we might leave the destination string
unterminated. Thus, use strlcpy() and also sizeof() while we're
at it. We need to memset the data area beforehand, since strlcpy
does not padd the remaining buffer with zeroes for user space, so
that we do not possibly leak anything.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index cfcd7835b6dd04a18c0a3a649f4ed97013e608b3..8ed5d9302e881a84e8becb07be810ba2d7da8324 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2848,12 +2848,11 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
                return -EOPNOTSUPP;
 
        uaddr->sa_family = AF_PACKET;
+       memset(uaddr->sa_data, 0, sizeof(uaddr->sa_data));
        rcu_read_lock();
        dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
        if (dev)
-               strncpy(uaddr->sa_data, dev->name, 14);
-       else
-               memset(uaddr->sa_data, 0, 14);
+               strlcpy(uaddr->sa_data, dev->name, sizeof(uaddr->sa_data));
        rcu_read_unlock();
        *uaddr_len = sizeof(*uaddr);