BUG/MINOR: config: check capture pool creations for failures

A few capture pools can fail in case of too large values for example.
These include the req_uri, capture, and caphdr pools, and may be triggered
with "tune.http.logurilen 2147483647" in the global section, or one of
these in a frontend:

  capture request header name len 2147483647
  http-request capture src len 2147483647
  tcp-request content capture src len 2147483647

These seem to be the only occurrences where create_pool()'s return value
is assigned without being checked, so let's add the proper check for
errors there. This can be backported as a hardening measure though the
risks and impacts are extremely low.

src/cfgparse.c

@@ -2324,6 +2324,12 @@ int check_config_validity()
 
 	pool_head_capture = create_pool("capture", global.tune.cookie_len, MEM_F_SHARED);
 
+	/* both will have already emitted an error message if needed */
+	if (!pool_head_requri || !pool_head_capture) {
+		err_code |= ERR_ALERT | ERR_FATAL;
+		goto out;
+	}
+
 	/* Post initialisation of the users and groups lists. */
 	err_code = userlist_postinit();
 	if (err_code != ERR_NONE)

src/http_act.c

@@ -960,6 +960,12 @@ static enum act_parse_ret parse_http_req_capture(const char **args, int *orig_ar
 		hdr->namelen = 0;
 		hdr->len = len;
 		hdr->pool = create_pool("caphdr", hdr->len + 1, MEM_F_SHARED);
+		if (!hdr->pool) {
+			memprintf(err, "out of memory");
+			free(hdr);
+			release_sample_expr(expr);
+			return ACT_RET_PRS_ERR;
+		}
 		hdr->index = px->nb_req_cap++;
 
 		px->req_cap = hdr;

src/proxy.c

@@ -878,6 +878,11 @@ static int proxy_parse_declare(char **args, int section, struct proxy *curpx,
 		hdr->namelen = 0;
 		hdr->len = len;
 		hdr->pool = create_pool("caphdr", hdr->len + 1, MEM_F_SHARED);
+		if (!hdr->pool) {
+			memprintf(err, "out of memory");
+			free(hdr);
+			return -1;
+		}
 
 		if (strcmp(args[2], "request") == 0) {
 			hdr->next = curpx->req_cap;

src/tcp_rules.c

@@ -970,6 +970,12 @@ static int tcp_parse_request_rule(char **args, int arg, int section_type,
 		hdr->namelen = 0;
 		hdr->len = len;
 		hdr->pool = create_pool("caphdr", hdr->len + 1, MEM_F_SHARED);
+		if (!hdr->pool) {
+			memprintf(err, "parsing [%s:%d] : out of memory", file, line);
+			free(hdr);
+			release_sample_expr(expr);
+			return -1;
+		}
 		hdr->index = curpx->nb_req_cap++;
 
 		curpx->req_cap = hdr;