netfilter: nft_range: add the missing NULL pointer check

Otherwise, kernel panic will happen if the user does not specify
the related attributes.

Fixes: 0f3cd9b3 ("netfilter: nf_tables: add range expression")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_range.c

@@ -59,6 +59,12 @@ static int nft_range_init(const struct nft_ctx *ctx, const struct nft_expr *expr
 	int err;
 	u32 op;
 
+	if (!tb[NFTA_RANGE_SREG]      ||
+	    !tb[NFTA_RANGE_OP]	      ||
+	    !tb[NFTA_RANGE_FROM_DATA] ||
+	    !tb[NFTA_RANGE_TO_DATA])
+		return -EINVAL;
+
 	err = nft_data_init(NULL, &priv->data_from, sizeof(priv->data_from),
 			    &desc_from, tb[NFTA_RANGE_FROM_DATA]);
 	if (err < 0)