[PATCH] hooks: fix a missing-check bug in selinux_add_mnt_opt()

[Gen Zhang]

In selinux_add_mnt_opt(), 'val' is allcoted by kmemdup_nul(). It returns
NULL when fails. So 'val' should be checked.

Signed-off-by: Gen Zhang <blackgod016...@gmail.com>
---
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702c..4797c63 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1052,8 +1052,11 @@ static int selinux_add_mnt_opt(const char *option, const 
char *val, int len,
        if (token == Opt_error)
                return -EINVAL;
 
-       if (token != Opt_seclabel)
-               val = kmemdup_nul(val, len, GFP_KERNEL);
+       if (token != Opt_seclabel) {
+                       val = kmemdup_nul(val, len, GFP_KERNEL);
+                       if (!val)
+                               return -ENOMEM;
+       }
        rc = selinux_add_opt(token, val, mnt_opts);
        if (unlikely(rc)) {
                kfree(val);