selinux: checkreqprot is deprecated, add some ssleep() discomfort

The checkreqprot functionality was disabled by default back in
Linux v4.4 (2015) with commit 2a35d19 ("selinux: change
CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE default") and it was
officially marked as deprecated in Linux v5.7.  It was always a
bit of a hack to workaround very old userspace and to the best of
our knowledge, the checkreqprot functionality has been disabled by
Linux distributions for quite some time.

This patch moves the deprecation messages from KERN_WARNING to
KERN_ERR and adds a five second sleep to anyone using it to help
draw their attention to the deprecation and provide a URL which
helps explain things in more detail.

Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: pcmoore

security/selinux/hooks.c

@@ -145,7 +145,7 @@ static int __init checkreqprot_setup(char *str)
 	if (!kstrtoul(str, 0, &checkreqprot)) {
 		selinux_checkreqprot_boot = checkreqprot ? 1 : 0;
 		if (checkreqprot)
-			pr_warn("SELinux: checkreqprot set to 1 via kernel parameter.  This is deprecated and will be rejected in a future kernel release.\n");
+			pr_err("SELinux: checkreqprot set to 1 via kernel parameter.  This is deprecated and will be rejected in a future kernel release.\n");
 	}
 	return 1;
 }
@@ -7293,6 +7293,8 @@ static __init int selinux_init(void)
 
 	memset(&selinux_state, 0, sizeof(selinux_state));
 	enforcing_set(&selinux_state, selinux_enforcing_boot);
+	if (CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE)
+		pr_err("SELinux: CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE is non-zero.  This is deprecated and will be rejected in a future kernel release.\n");
 	checkreqprot_set(&selinux_state, selinux_checkreqprot_boot);
 	selinux_avc_init(&selinux_state.avc);
 	mutex_init(&selinux_state.status_lock);

security/selinux/include/security.h

@@ -16,6 +16,8 @@
 #include <linux/rcupdate.h>
 #include <linux/refcount.h>
 #include <linux/workqueue.h>
+#include <linux/delay.h>
+#include <linux/printk.h>
 #include "flask.h"
 #include "policycap.h"
 
@@ -150,6 +152,10 @@ static inline bool checkreqprot_get(const struct selinux_state *state)
 
 static inline void checkreqprot_set(struct selinux_state *state, bool value)
 {
+	if (value) {
+		pr_err("SELinux: https://github.com/SELinuxProject/selinux-kernel/wiki/DEPRECATE-checkreqprot\n");
+		ssleep(5);
+	}
 	WRITE_ONCE(state->checkreqprot, value);
 }
 

security/selinux/selinuxfs.c

@@ -757,8 +757,8 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
 		char comm[sizeof(current->comm)];
 
 		memcpy(comm, current->comm, sizeof(comm));
-		pr_warn_once("SELinux: %s (%d) set checkreqprot to 1. This is deprecated and will be rejected in a future kernel release.\n",
-			     comm, current->pid);
+		pr_err("SELinux: %s (%d) set checkreqprot to 1. This is deprecated and will be rejected in a future kernel release.\n",
+		       comm, current->pid);
 	}
 
 	checkreqprot_set(fsi->state, (new_value ? 1 : 0));