commit 444dad86beaaa60bd96790c7097aa66bb331e645
from: Omar Polo <op@omarpolo.com>
date: Thu Oct 07 21:57:04 2021 UTC

dirname fix

dirname(3) is really one of the worst part of POSIX, portability-wise.
Implementors can decide to either modify the passed string or return a
pointer to an internal storage.

The current code fails when dirname returns a pointer to an internal
storage because between the strcmp call and the mkdir we go into a
recursion that can modify `path'.  We can't use copy either because
*some* implementation of dirname would have changed that.

How to escape from this hell?  Take yet another copy of the path!

commit - eb2ed626f304f3f1e00711c20d76ecfd8dcc5ce7
commit + 444dad86beaaa60bd96790c7097aa66bb331e645
blob - fe5290ef682562a940933715bda1bf34554c84d7
blob + e645e7b3ee272bc80cbf72eb8d497f07c7520b1b
--- fs.c
+++ fs.c
@@ -581,18 +581,19 @@ getenv_default(char *buf, const char *name, const char
 static void
 mkdirs(const char *path, mode_t mode)
 {
-	char copy[PATH_MAX+1], *parent;
+	char copy[PATH_MAX+1], orig[PATH_MAX+1], *parent;
 
 	strlcpy(copy, path, sizeof(copy));
+	strlcpy(orig, path, sizeof(orig));
 	parent = dirname(copy);
 	if (!strcmp(parent, "/"))
 		return;
 	mkdirs(parent, mode);
 
-	if (mkdir(path, mode) != 0) {
+	if (mkdir(orig, mode) != 0) {
 		if (errno == EEXIST)
 			return;
-		err(1, "can't mkdir %s", path);
+		err(1, "can't mkdir %s", orig);
 	}
 }