vxlan: Avoid infinite loop when suppressing NS messages with invalid options

[ Upstream commit 8066e6b449e050675df48e7c4b16c29f00507ff0 ]

When proxy mode is enabled the vxlan device might reply to Neighbor
Solicitation (NS) messages on behalf of remote hosts.

In case the NS message includes the "Source link-layer address" option
[1], the vxlan device will use the specified address as the link-layer
destination address in its reply.

To avoid an infinite loop, break out of the options parsing loop when
encountering an option with length zero and disregard the NS message.

This is consistent with the IPv6 ndisc code and RFC 4886 which states
that "Nodes MUST silently discard an ND packet that contains an option
with length zero" [2].

[1] https://tools.ietf.org/html/rfc4861#section-4.3
[2] https://tools.ietf.org/html/rfc4861#section-4.6

Fixes: 4b29dba9c085 ("vxlan: fix nonfunctional neigh_reduce()")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index a5b415fed11efb8c6e2dcd30554ea6c10835d0ab..779e56c43d27b26f18bea8a45d93285702891bda 100644 (file)
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1924,6 +1924,10 @@ static struct sk_buff *vxlan_na_create(struct sk_buff *request,
        ns_olen = request->len - skb_network_offset(request) -
                sizeof(struct ipv6hdr) - sizeof(*ns);
        for (i = 0; i < ns_olen-1; i += (ns->opt[i+1]<<3)) {
+               if (!ns->opt[i + 1]) {
+                       kfree_skb(reply);
+                       return NULL;
+               }
                if (ns->opt[i] == ND_OPT_SOURCE_LL_ADDR) {
                        daddr = ns->opt + i + sizeof(struct nd_opt_hdr);
                        break;