SELinux: Abstract use of inode security blob

Don't use the inode->i_security pointer directly.
Provide a helper function that provides the security blob pointer.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

security/selinux/include/objsec.h

@@ -170,4 +170,10 @@ static inline struct file_security_struct *selinux_file(const struct file *file)
 	return file->f_security + selinux_blob_sizes.lbs_file;
 }
 
+static inline struct inode_security_struct *selinux_inode(
+						const struct inode *inode)
+{
+	return inode->i_security;
+}
+
 #endif /* _SELINUX_OBJSEC_H_ */