kernel/sys.c: avoid argv_free(NULL)

If argv_split() failed, the code will end up calling argv_free(NULL).  Fix
it up and clean things up a bit.

Addresses Coverity report 703573.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sys.c

@@ -2186,46 +2186,52 @@ static void argv_cleanup(struct subprocess_info *info)
 	argv_free(info->argv);
 }
 
-/**
- * orderly_poweroff - Trigger an orderly system poweroff
- * @force: force poweroff if command execution fails
- *
- * This may be called from any context to trigger a system shutdown.
- * If the orderly shutdown fails, it will force an immediate shutdown.
- */
-int orderly_poweroff(bool force)
+static int __orderly_poweroff(void)
 {
 	int argc;
-	char **argv = argv_split(GFP_ATOMIC, poweroff_cmd, &argc);
+	char **argv;
 	static char *envp[] = {
 		"HOME=/",
 		"PATH=/sbin:/bin:/usr/sbin:/usr/bin",
 		NULL
 	};
-	int ret = -ENOMEM;
+	int ret;
 
+	argv = argv_split(GFP_ATOMIC, poweroff_cmd, &argc);
 	if (argv == NULL) {
 		printk(KERN_WARNING "%s failed to allocate memory for \"%s\"\n",
 		       __func__, poweroff_cmd);
-		goto out;
+		return -ENOMEM;
 	}
 
 	ret = call_usermodehelper_fns(argv[0], argv, envp, UMH_NO_WAIT,
 				      NULL, argv_cleanup, NULL);
-out:
-	if (likely(!ret))
-		return 0;
-
 	if (ret == -ENOMEM)
 		argv_free(argv);
 
-	if (force) {
+	return ret;
+}
+
+/**
+ * orderly_poweroff - Trigger an orderly system poweroff
+ * @force: force poweroff if command execution fails
+ *
+ * This may be called from any context to trigger a system shutdown.
+ * If the orderly shutdown fails, it will force an immediate shutdown.
+ */
+int orderly_poweroff(bool force)
+{
+	int ret = __orderly_poweroff();
+
+	if (ret && force) {
 		printk(KERN_WARNING "Failed to start orderly shutdown: "
 		       "forcing the issue\n");
 
-		/* I guess this should try to kick off some daemon to
-		   sync and poweroff asap.  Or not even bother syncing
-		   if we're doing an emergency shutdown? */
+		/*
+		 * I guess this should try to kick off some daemon to sync and
+		 * poweroff asap.  Or not even bother syncing if we're doing an
+		 * emergency shutdown?
+		 */
 		emergency_sync();
 		kernel_power_off();
 	}