vxlan: validate ND option lengths in vxlan_na_create

commit afa9a05e6c4971bd5586f1b304e14d61fb3d9385 upstream.

vxlan_na_create() walks ND options according to option-provided
lengths. A malformed option can make the parser advance beyond the
computed option span or use a too-short source LLADDR option payload.

Validate option lengths against the remaining NS option area before
advancing, and only read source LLADDR when the option is large enough
for an Ethernet address.

Fixes: 4b29dba9c085 ("vxlan: fix nonfunctional neigh_reduce()")
Cc: stable@vger.kernel.org
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Tested-by: Ao Zhou <n05ec@lzu.edu.cn>
Co-developed-by: Yuan Tan <tanyuan98@outlook.com>
Signed-off-by: Yuan Tan <tanyuan98@outlook.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Yang Yang <n05ec@lzu.edu.cn>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260326034441.2037420-4-n05ec@lzu.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 2a140be86bafc0ec01a57866096f545307666c05..d2d0e0bd43716cb9641fb336efabdaf3011d1c5f 100644 (file)
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -1965,12 +1965,14 @@ 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]) {
+               if (!ns->opt[i + 1] || i + (ns->opt[i + 1] << 3) > ns_olen) {
                        kfree_skb(reply);
                        return NULL;
                }
                if (ns->opt[i] == ND_OPT_SOURCE_LL_ADDR) {
-                       daddr = ns->opt + i + sizeof(struct nd_opt_hdr);
+                       if ((ns->opt[i + 1] << 3) >=
+                           sizeof(struct nd_opt_hdr) + ETH_ALEN)
+                               daddr = ns->opt + i + sizeof(struct nd_opt_hdr);
                        break;
                }
        }