Fix logic for directory creation when saving state

When creating the /tmp/brightnessctl directory or its subdirectories, clear
errno before calling mkdir, and call stat a second time after mkdir.

Previously, errno was not cleared, so even if the error was handled (by
creating the missing directory with mkdir), subsequent error handling code
read the old errno value from the failed stat call and printed an error
message.

Additionally, because we did not call stat again after calling mkdir, the
stat buffer had outdated information, and so S_ISDIR returned a false
negative.

As a result of these defects, invoking brightnessctl -s when
/tmp/brightnessctl did not exist would create /tmp/brightnessctl and fail.
Invoking brightnessctl -s a second time would create
/tmp/brightnessctl/backlight and fail. Invoking the command a third time
would succeed and write the state file under /tmp/brightnessctl/backlight/.
After this commit, brightnessctl -s succeeds the first time.

1 files changed, 6 insertions, 0 deletions

diff --git a/brightnessctl.c b/brightnessctl.c
index 86a0e21..3f7cfc1 100644
--- a/brightnessctl.c
+++ b/brightnessctl.c
@@ -395,8 +395,11 @@ int save_device_data(struct device *dev) {
 	if (stat(c_path, &sb)) {
 		if (errno != ENOENT)
 			goto fail;
+		errno = 0;
 		if (mkdir(c_path, 0777))
 			goto fail;
+		if (stat(c_path, &sb))
+			goto fail;
 	}
 	if (!S_ISDIR(sb.st_mode))
 		goto fail;
@@ -442,9 +445,12 @@ static int ensure_run_dir() {
 	if (stat(run_dir, &sb)) {
 		if (errno != ENOENT)
 			return 0;
+		errno = 0;
 		if (mkdir(run_dir, 0777)) {
 			return 0;
 		}
+		if (stat(run_dir, &sb))
+			return 0;
 	}
 	return S_ISDIR(sb.st_mode);
 }