hard-wire legacy checkreqprot option to 0

The userspace API is left intact for compatibility.

Author: thestinger

Documentation/admin-guide/kernel-parameters.txt

@@ -490,16 +490,6 @@
 			nosocket -- Disable socket memory accounting.
 			nokmem -- Disable kernel memory accounting.
 
-	checkreqprot	[SELINUX] Set initial checkreqprot flag value.
-			Format: { "0" | "1" }
-			See security/selinux/Kconfig help text.
-			0 -- check protection applied by kernel (includes
-				any implied execute protection).
-			1 -- check protection requested by application.
-			Default value is set via a kernel config option.
-			Value can be changed at runtime via
-				/selinux/checkreqprot.
-
 	cio_ignore=	[S390]
 			See Documentation/s390/CommonIO for details.
 	clk_ignore_unused

security/selinux/Kconfig

@@ -79,23 +79,3 @@ config SECURITY_SELINUX_AVC_STATS
 	  This option collects access vector cache statistics to
 	  /selinux/avc/cache_stats, which may be monitored via
 	  tools such as avcstat.
-
-config SECURITY_SELINUX_CHECKREQPROT_VALUE
-	int "NSA SELinux checkreqprot default value"
-	depends on SECURITY_SELINUX
-	range 0 1
-	default 0
-	help
-	  This option sets the default value for the 'checkreqprot' flag
-	  that determines whether SELinux checks the protection requested
-	  by the application or the protection that will be applied by the
-	  kernel (including any implied execute for read-implies-exec) for
-	  mmap and mprotect calls.  If this option is set to 0 (zero),
-	  SELinux will default to checking the protection that will be applied
-	  by the kernel.  If this option is set to 1 (one), SELinux will
-	  default to checking the protection requested by the application.
-	  The checkreqprot flag may be changed from the default via the
-	  'checkreqprot=' boot parameter.  It may also be changed at runtime
-	  via /selinux/checkreqprot if authorized by policy.
-
-	  If you are unsure how to answer this question, answer 0.

security/selinux/include/objsec.h

@@ -150,6 +150,6 @@ struct pkey_security_struct {
 	u32	sid;	/* SID of pkey */
 };
 
-extern unsigned int selinux_checkreqprot;
+extern const unsigned int selinux_checkreqprot;
 
 #endif /* _SELINUX_OBJSEC_H_ */

security/selinux/selinuxfs.c

@@ -41,16 +41,7 @@
 #include "objsec.h"
 #include "conditional.h"
 
-unsigned int selinux_checkreqprot = CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE;
-
-static int __init checkreqprot_setup(char *str)
-{
-	unsigned long checkreqprot;
-	if (!kstrtoul(str, 0, &checkreqprot))
-		selinux_checkreqprot = checkreqprot ? 1 : 0;
-	return 1;
-}
-__setup("checkreqprot=", checkreqprot_setup);
+const unsigned int selinux_checkreqprot;
 
 static DEFINE_MUTEX(sel_mutex);
 
@@ -610,10 +601,9 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
 		return PTR_ERR(page);
 
 	length = -EINVAL;
-	if (sscanf(page, "%u", &new_value) != 1)
+	if (sscanf(page, "%u", &new_value) != 1 || new_value)
 		goto out;
 
-	selinux_checkreqprot = new_value ? 1 : 0;
 	length = count;
 out:
 	kfree(page);