tomoyo: fix potential use after free

The original code returns a freed pointer.  This function is expected to
return NULL on errors.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>

security/tomoyo/common.c

@@ -886,6 +886,7 @@ static struct tomoyo_profile *tomoyo_find_or_assign_new_profile(const unsigned
 	ptr = kmalloc(sizeof(*ptr), GFP_KERNEL);
 	if (!tomoyo_memory_ok(ptr)) {
 		kfree(ptr);
+		ptr = NULL;
 		goto ok;
 	}
 	for (i = 0; i < TOMOYO_MAX_CONTROL_INDEX; i++)