netfilter: nft_compat: use-after-free when deleting targets

Fetch pointer to module before target object is released.

Fixes: 29e38801 ("netfilter: nf_tables: fix use-after-free when deleting compat expressions")
Fixes: 0ca743a5 ("netfilter: nf_tables: add compatibility layer for x_tables")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_compat.c

@@ -315,6 +315,7 @@ nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
 {
 	struct xt_target *target = expr->ops->data;
 	void *info = nft_expr_priv(expr);
+	struct module *me = target->me;
 	struct xt_tgdtor_param par;
 
 	par.net = ctx->net;
@@ -325,7 +326,7 @@ nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
 		par.target->destroy(&par);
 
 	if (nft_xt_put(container_of(expr->ops, struct nft_xt, ops)))
-		module_put(target->me);
+		module_put(me);
 }
 
 static int nft_extension_dump_info(struct sk_buff *skb, int attr,