[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 <blackgod016574@xxxxxxxxx>
Reviewed-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
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)) {