cache_lock: do xstrdup/free on lockfile

Since fmt() uses 8 alternating static buffers, and cache_lock might call
cache_create_dirs() multiple times, which in turn might call fmt() twice,
after four iterations lockfile would be overwritten by a cachedirectory
path.

In worst case, this could cause the cachedirectory to be unlinked and replaced
by a cachefile.

Fix: use xstrdup() on the result from fmt() before assigning to lockfile, and
call free(lockfile) before exit.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/cache.c b/cache.c
index b947a34..39e63a5 100644
--- a/cache.c
+++ b/cache.c
@@ -65,40 +65,41 @@ int cache_refill_overdue(const char *lockfile)
 {
 	struct stat st;
 
 	if (stat(lockfile, &st))
 		return 0;
 	else
 		return (time(NULL) - st.st_mtime > cgit_cache_max_create_time);
 }
 
 int cache_lock(struct cacheitem *item)
 {
 	int i = 0;
-	char *lockfile = fmt("%s.lock", item->name);
+	char *lockfile = xstrdup(fmt("%s.lock", item->name));
 
  top:
 	if (++i > cgit_max_lock_attempts)
 		die("cache_lock: unable to lock %s: %s",
 		    item->name, strerror(errno));
 
        	item->fd = open(lockfile, O_WRONLY|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR);
 
 	if (item->fd == NOLOCK && errno == ENOENT && cache_create_dirs())
 		goto top;
 
 	if (item->fd == NOLOCK && errno == EEXIST &&
 	    cache_refill_overdue(lockfile) && !unlink(lockfile))
 			goto top;
 
+	free(lockfile);
 	return (item->fd > 0);
 }
 
 int cache_unlock(struct cacheitem *item)
 {
 	close(item->fd);
 	return (rename(fmt("%s.lock", item->name), item->name) == 0);
 }
 
 int cache_cancel_lock(struct cacheitem *item)
 {
 	return (unlink(fmt("%s.lock", item->name)) == 0);