netlink_delinearize: Sanitize concat data element decoding

The call to netlink_get_register() might return NULL, catch this before
dereferencing the pointer.

Fixes: db59a5c1204c9 ("netlink_delinearize: fix decoding of concat data element")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Acked-by: Florian Westphal <fw@strlen.de>

diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c
index f4ab476e0345584731cf6a466b7cfbad4c3e092e..00221505f2899034b564691dfcf016604aecb82b 100644 (file)
--- a/src/netlink_delinearize.c
+++ b/src/netlink_delinearize.c
@@ -1749,7 +1749,7 @@ static void netlink_parse_dynset(struct netlink_parse_ctx *ctx,
                sreg_data = netlink_parse_register(nle, NFTNL_EXPR_DYNSET_SREG_DATA);
                expr_data = netlink_get_register(ctx, loc, sreg_data);
 
-               if (expr_data->len < set->data->len) {
+               if (expr_data && expr_data->len < set->data->len) {
                        expr_free(expr_data);
                        expr_data = netlink_parse_concat_expr(ctx, loc, sreg_data, set->data->len);
                        if (expr_data == NULL)