util/mkhtemp: show path on error accessing it

a bit naughty the way i do it, but it works. without
this, the message gets clobbered by EINVAL due to
a bad call to vprintf in the err function.

in this way, we ensure that there is a path, and
thus the errno does not get clobbered. i also
removed the EPERM setting in the env_tmpdir
function, which also clobbered errno.

with this fix, if TMPDIR is set but invalid,
it should now show the error reliably.

Signed-off-by: Leah Rowe <leah@libreboot.org>

1 files changed, 25 insertions, 8 deletions

diff --git a/util/libreboot-utils/lib/mkhtemp.c b/util/libreboot-utils/lib/mkhtemp.c
index 8d58dcc5..e1ca0a10 100644
--- a/util/libreboot-utils/lib/mkhtemp.c
+++ b/util/libreboot-utils/lib/mkhtemp.c
@@ -63,6 +63,8 @@ new_tmp_common(int *fd, char **path, int type)
 
 	struct stat st_dir_initial;
 
+	char *fail_dir = NULL;
+
 	if (path == NULL || fd == NULL) {
 		errno = EFAULT;
 		goto err;
@@ -89,9 +91,9 @@ new_tmp_common(int *fd, char **path, int type)
 
 #if defined(PERMIT_NON_STICKY_ALWAYS) && \
     ((PERMIT_NON_STICKY_ALWAYS) > 0)
-	tmpdir = env_tmpdir(PERMIT_NON_STICKY_ALWAYS);
+	tmpdir = env_tmpdir(PERMIT_NON_STICKY_ALWAYS, &fail_dir);
 #else
-	tmpdir = env_tmpdir(0);
+	tmpdir = env_tmpdir(0, &fail_dir);
 #endif
 	if (tmpdir == NULL)
 		goto err;
@@ -176,6 +178,13 @@ err:
 		*fd = -1;
 	}
 
+	/* where a TMPDIR isn't found, and we err,
+	 * we pass this back through for the
+	 * error message
+	 */
+	if (fail_dir != NULL)
+		*path = fail_dir;
+
 	errno = saved_errno;
 	return -1;
 }
@@ -185,26 +194,31 @@ err:
  */
 
 char *
-env_tmpdir(int bypass_all_sticky_checks)
+env_tmpdir(int bypass_all_sticky_checks, char **tmpdir)
 {
 	char *t;
 	int allow_noworld_unsticky;
 	int saved_errno = errno;
 
+	char tmp[] = "/tmp";
+	char vartmp[] = "/var/tmp";
+
 	t = getenv("TMPDIR");
 
 	if (t != NULL && *t != '\0') {
 
 		if (tmpdir_policy(t,
 		    &allow_noworld_unsticky) < 0) {
-			errno = EPERM;
+			if (tmpdir != NULL)
+				*tmpdir = t;
 			return NULL; /* errno already set */
 		}
 
 		if (!world_writeable_and_sticky(t,
 		    allow_noworld_unsticky,
 		    bypass_all_sticky_checks)) {
-			errno = EPERM;
+			if (tmpdir != NULL)
+				*tmpdir = t;
 			return NULL;
 		}
 
@@ -218,6 +232,9 @@ env_tmpdir(int bypass_all_sticky_checks)
 	    allow_noworld_unsticky,
 	    bypass_all_sticky_checks)) {
 
+		if (tmpdir != NULL)
+			*tmpdir = tmp;
+
 		errno = saved_errno;
 		return "/tmp";
 	}
@@ -226,13 +243,13 @@ env_tmpdir(int bypass_all_sticky_checks)
 	    allow_noworld_unsticky,
 	    bypass_all_sticky_checks)) {
 
+		if (tmpdir != NULL)
+			*tmpdir = vartmp;
+
 		errno = saved_errno;
 		return "/var/tmp";
 	}
 
-	if (errno == saved_errno)
-		errno = EPERM;
-
 	return NULL;
 }