fix possible out-of-bound access

While computing the parent directory it an out-of-bound access can
occur, which usually means the server process dies.

In particular, it can be triggered by making a request for a
non-existent file in the root of a virtual host if the path matches
the `cgi` pattern.

Thanks cage for helping in debugging!

1 files changed, 5 insertions, 1 deletions

diff --git a/server.c b/server.c
index 473e111..e07d6bc 100644
--- a/server.c
+++ b/server.c
@@ -406,8 +406,12 @@ check_for_cgi(struct client *c)
 		 * dirname, with its ambiguities on if the given
 		 * pointer is changed or not, gives me headaches.
 		 */
-		while (*end != '/')
+		while (*end != '/' && end > path)
 			end--;
+
+		if (end == path)
+			break;
+
 		*end = '\0';
 
 		switch (check_path(c, path, &c->pfd)) {