conf: ignore the prefix if the config file name is an absolute path

Fixes:
$ export PIPEWIRE_CONFIG_PREFIX=/usr/share/pipewire
$ pipewire -c /etc/pipewire/bar.conf
[W][11925.530591][          conf.c:  253 conf_load()] config 0x560039ac6510: error loading config '/usr/share/pipewire//etc/pipewire/pipewire.conf': No such file or directory
[W][11925.530721][       context.c:  178 try_load_conf()] context 0x560039ac6190: can't load config /usr/share/pipewire//etc/pipewire/pipewire.conf: No such file or directory

src/pipewire/conf.c

@@ -69,13 +69,27 @@ static int get_read_path(char *path, size_t size, const char *prefix, const char
 	const char *dir;
 	char buffer[4096];
 
-	if (prefix[0] == '/') {
+	if (name[0] == '/') {
+		const char *paths[] = { name, NULL };
+		if (make_path(path, size, paths) == 0 &&
+		    access(path, R_OK) == 0)
+			return 1;
+		return -ENOENT;
+	}
+
+	if (prefix && prefix[0] == '/') {
 		const char *paths[] = { prefix, name, NULL };
 		if (make_path(path, size, paths) == 0 &&
 		    access(path, R_OK) == 0)
 			return 1;
 		return -ENOENT;
 	}
+
+	if (prefix == NULL) {
+		prefix = name;
+		name = NULL;
+	}
+
 	if (pw_check_option("no-config", "true"))
 		goto no_config;
 
@@ -240,11 +254,6 @@ static int conf_load(const char *prefix, const char *name, struct pw_properties
 	struct stat sbuf;
 	int fd;
 
-	if (prefix == NULL) {
-		prefix = name;
-		name = NULL;
-	}
-
 	if (get_read_path(path, sizeof(path), prefix, name) == 0) {
 		pw_log_debug(NAME" %p: can't load config '%s': %m", conf, path);
 		return -ENOENT;

src/pipewire/context.c

@@ -175,10 +175,11 @@ static int try_load_conf(struct pw_context *this, const char *conf_prefix,
 	if (spa_streq(conf_name, "null"))
 		return 0;
 	if ((res = pw_conf_load_conf(conf_prefix, conf_name, conf)) < 0) {
+		bool skip_prefix = conf_prefix == NULL || conf_name[0] == '/';
 		pw_log_warn(NAME" %p: can't load config %s%s%s: %s",
 				this,
-				conf_prefix ? conf_prefix : "",
-				conf_prefix ? "/" : "",
+				skip_prefix ? "" : conf_prefix,
+				skip_prefix ? "" : "/",
 				conf_name, spa_strerror(res));
 	}
 	return res;

test/meson.build

@@ -63,6 +63,7 @@ test('test lib',
 test('test context',
     executable('test-context',
                'test-context.c',
+               'test-config.c',
                include_directories: pwtest_inc,
                link_with: pwtest_lib)
 )

test/test-config.c

@@ -0,0 +1,83 @@
+/* PipeWire
+ *
+ * Copyright © 2021 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "pwtest.h"
+
+#include <pipewire/conf.h>
+
+PWTEST(config_load_abspath)
+{
+	char path[PATH_MAX];
+	int r;
+	FILE *fp;
+	struct pw_properties *props;
+	char *basename;
+
+	pwtest_mkstemp(path);
+	fp = fopen(path, "w");
+	fputs("data = x", fp);
+	fclose(fp);
+
+	/* Load with NULL prefix and abs path */
+	props = pw_properties_new("ignore", "me", NULL);
+	r = pw_conf_load_conf(NULL, path, props);
+	pwtest_neg_errno_ok(r);
+	pwtest_str_eq(pw_properties_get(props, "data"), "x");
+	pw_properties_free(props);
+
+	/* Load with non-NULL abs prefix and abs path */
+	props = pw_properties_new("ignore", "me", NULL);
+	r = pw_conf_load_conf("/dummy", path, props);
+	pwtest_neg_errno_ok(r);
+	pwtest_str_eq(pw_properties_get(props, "data"), "x");
+	pw_properties_free(props);
+
+	/* Load with non-NULL relative prefix and abs path */
+	props = pw_properties_new("ignore", "me", NULL);
+	r = pw_conf_load_conf("dummy", path, props);
+	pwtest_neg_errno_ok(r);
+	pwtest_str_eq(pw_properties_get(props, "data"), "x");
+	pw_properties_free(props);
+
+	/* Load with non-NULL abs prefix and relative path */
+	basename = rindex(path, '/'); /* basename(3) and dirname(3) are terrible */
+	pwtest_ptr_notnull(basename);
+	*basename = '\0';
+	basename++;
+
+	props = pw_properties_new("ignore", "me", NULL);
+	r = pw_conf_load_conf(path, basename, props);
+	pwtest_neg_errno_ok(r);
+	pwtest_str_eq(pw_properties_get(props, "data"), "x");
+	pw_properties_free(props);
+
+	return PWTEST_PASS;
+}
+
+PWTEST_SUITE(context)
+{
+	pwtest_add(config_load_abspath, PWTEST_NOARG);
+
+	return PWTEST_PASS;
+}