threads / patch / 35745

patch, 2 partsexpand_user_path: do not look at NULL path

Subject: [PATCH 1/2] expand_user_path: do not look at NULL path

## tl;dr

2 messages between Jan 28, 2014 and Jan 28, 2014. Diffs are folded; open one to read it.

replies: 1people: 1as markdown or json

Jeff King· Jan 28, 2014, 01:36 UTC · lore

We explicitly check for and handle the case that the incoming "path" variable is NULL, but before doing so we call strchrnul on it, leading to a potential segfault.

We can fix this simply by moving the strchrnul call down; as a bonus, we can tighten the scope on the associated variable.

Signed-off-by: Jeff King <peff@peff.net>
---
Most of the callers already check for NULL, so the only way to trigger
this is via an empty "include.path". That is addressed separately in the
next patch, so technically this is not needed if we apply that one. But
in that case, the "path == NULL" check here is useless, so I think this
makes things safer overall.

 path.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Show changes to path.c +1 −1

diff --git a/path.c b/path.c
index 24594c4..f9c5062 100644
--- a/path.c
+++ b/path.c
@@ -265,12 +265,12 @@ static struct passwd *getpw_str(const char *username, size_t len)
 char *expand_user_path(const char *path)
 {
 	struct strbuf user_path = STRBUF_INIT;
-	const char *first_slash = strchrnul(path, '/');
 	const char *to_copy = path;
 
 	if (path == NULL)
 		goto return_null;
 	if (path[0] == '~') {
+		const char *first_slash = strchrnul(path, '/');
 		const char *username = path + 1;
 		size_t username_len = first_slash - username;
 		if (username_len == 0) {

-- 
1.8.5.2.500.g8060133

Jeff King· Jan 28, 2014, 01:37 UTC · re: Jeff King · lore

[PATCH 2/2] handle_path_include: don't look at NULL value

When we see config like:

  [include]
  path

the expand_user_path helper notices that the config value is empty, but we then dereference NULL while printing the error message (glibc will helpfully print "(null)" for us here, but we cannot rely on that).

  $ git -c include.path rev-parse
  error: Could not expand include path '(null)'
  fatal: unable to parse command-line config

Instead of tweaking our message, let's actually use config_error_nonbool to match other config variables that expect a value:

  $ git -c include.path rev-parse
  error: Missing value for 'include.path'
  fatal: unable to parse command-line config

Signed-off-by: Jeff King <peff@peff.net>
---
 config.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Show changes to config.c +5 −1

diff --git a/config.c b/config.c
index d969a5a..314d8ee 100644
--- a/config.c
+++ b/config.c
@@ -84,8 +84,12 @@ static int handle_path_include(const char *path, struct config_include_data *inc
 {
 	int ret = 0;
 	struct strbuf buf = STRBUF_INIT;
-	char *expanded = expand_user_path(path);
+	char *expanded;
 
+	if (!path)
+		return config_error_nonbool("include.path");
+
+	expanded = expand_user_path(path);
 	if (!expanded)
 		return error("Could not expand include path '%s'", path);
 	path = expanded;

-- 
1.8.5.2.500.g8060133