git-config: fix regexp memory leaks on error conditions

The get_value function has a goto label for cleaning up on
errors, but it only cleans up half of what the function
might allocate. Let's also clean up the key and regexp
variables there.

Note that we need to take special care when compiling the
regex fails to clean it up ourselves, since it is in a
half-constructed state (we would want to free it, but not
regfree it).

Similarly, we fix git_config_parse_key to return NULL when
it fails, not a pointer to some already-freed memory.

Signed-off-by: Jeff King <peff@peff.net>

2 files changed, 14 insertions, 10 deletions

diff --git a/builtin/config.c b/builtin/config.c
index e660d4830..60d36e734 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -195,7 +195,8 @@ static int get_value(const char *key_, const char *regex_)
 		key_regexp = (regex_t*)xmalloc(sizeof(regex_t));
 		if (regcomp(key_regexp, key, REG_EXTENDED)) {
 			fprintf(stderr, "Invalid key pattern: %s\n", key_);
-			free(key);
+			free(key_regexp);
+			key_regexp = NULL;
 			ret = CONFIG_INVALID_PATTERN;
 			goto free_strings;
 		}
@@ -215,6 +216,8 @@ static int get_value(const char *key_, const char *regex_)
 		regexp = (regex_t*)xmalloc(sizeof(regex_t));
 		if (regcomp(regexp, regex_, REG_EXTENDED)) {
 			fprintf(stderr, "Invalid pattern: %s\n", regex_);
+			free(regexp);
+			regexp = NULL;
 			ret = CONFIG_INVALID_PATTERN;
 			goto free_strings;
 		}
@@ -247,6 +250,15 @@ static int get_value(const char *key_, const char *regex_)
 	if (!do_all && !seen && system_wide)
 		git_config_from_file(fn, system_wide, data);
 
+	if (do_all)
+		ret = !seen;
+	else
+		ret = (seen == 1) ? 0 : seen > 1 ? 2 : 1;
+
+free_strings:
+	free(repo_config);
+	free(global);
+	free(xdg);
 	free(key);
 	if (key_regexp) {
 		regfree(key_regexp);
@@ -257,15 +269,6 @@ static int get_value(const char *key_, const char *regex_)
 		free(regexp);
 	}
 
-	if (do_all)
-		ret = !seen;
-	else
-		ret = (seen == 1) ? 0 : seen > 1 ? 2 : 1;
-
-free_strings:
-	free(repo_config);
-	free(global);
-	free(xdg);
 	return ret;
 }
 
diff --git a/config.c b/config.c
index 08e47e2e4..2fbe634b1 100644
--- a/config.c
+++ b/config.c
@@ -1280,6 +1280,7 @@ int git_config_parse_key(const char *key, char **store_key, int *baselen_)
 
 out_free_ret_1:
 	free(*store_key);
+	*store_key = NULL;
 	return -CONFIG_INVALID_KEY;
 }