[PATCH v2] hooks: fix a missing-check bug in selinux_sb_eat_lsm_opts()

[Gen Zhang]

In selinux_sb_eat_lsm_opts(), 'arg' is allocated by kmemdup_nul(). It
returns NULL when fails. So 'arg' should be checked.

Signed-off-by: Gen Zhang <blackgod016...@gmail.com>
Fixes: 99dbbb593fe6 ("selinux: rewrite selinux_sb_eat_lsm_opts()")
---
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702c..5a9e959 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2635,6 +2635,8 @@ static int selinux_sb_eat_lsm_opts(char *options, void 
**mnt_opts)
                                                *q++ = c;
                                }
                                arg = kmemdup_nul(arg, q - arg, GFP_KERNEL);
+                               if (!arg)
+                                       return -ENOMEM;
                        }
                        rc = selinux_add_opt(token, arg, mnt_opts);
                        if (unlikely(rc)) {