libebgenv: Only release CONFIG_PART::mountpoint early on errors

This fixes a regression caused by premature cleanup: If
probe_config_file() ran successfully and found an already mounted
partition, its mountpoint must not be released yet. bgenv_finalize()
will take care of that.

However, if probe_config_file() failed, it must free any previously
created mountpoint string prior to returning. That is what c2be7c1
was actually trying to resolve.

Reported-by: Ingo Rah <ingo.rah@linutronix.de>
Fixes: c2be7c1 ("libebgenv: fix memory leak in partition probing")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

Author: jan-kiszka

env/env_config_file.c

@@ -85,7 +85,7 @@ bool probe_config_file(CONFIG_PART *cfgpart)
 		}
 		if (do_unmount) {
 			unmount_partition(cfgpart);
-		} else {
+		} else if (!result) {
 			free(cfgpart->mountpoint);
 			cfgpart->mountpoint = NULL;
 		}