linux-kernel - Re: [kernel-hardening] [RFC V2 0/6] add more kernel pointer filter options

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Message-ID: <20171004085756.GD28247@kroah.com>
Date:   Wed, 4 Oct 2017 10:57:56 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        William Roberts <william.c.roberts@...el.com>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>
Subject: Re: [kernel-hardening] [RFC V2 0/6] add more kernel pointer filter
 options

On Sun, Oct 01, 2017 at 11:11:05AM +1100, Tobin C. Harding wrote:
> On Sun, Oct 01, 2017 at 11:06:44AM +1100, Tobin C. Harding wrote:
> > Version 2 of Greg's patch series with changes made as suggested by comments to V1.
> 
> Patch set tested by setting /proc/sys/kernel/kptr_restrict and inserting the following module
> 
> #include <linux/init.h>
> #include <linux/module.h>
> 
> #define DRIVER_AUTHOR "Tobin C. Harding <me@...in.cc>"
> #define DRIVER_DESC "Testing module"
> 
> static void test_printk(void)
> {
> 	char *ptr = "";
> 
> 	pr_alert("printing with p: %p\n", ptr);
> 	pr_alert("printing with pK: %pK\n", ptr);
> 	pr_alert("printing with pP: %pP\n", ptr);
> 
> 	pr_alert("printing with pa: %pa\n", ptr);
> 	pr_alert("printing with pad: %pad\n", ptr);
> 	pr_alert("printing with pap: %pap\n", ptr);
> 
> 	pr_alert("printing with paP: %paP\n", ptr);
> 	pr_alert("printing with padP: %padP\n", ptr);
> 	pr_alert("printing with papP: %papP\n", ptr);
> 
> 	pr_alert("printing with pr: %pr\n", ptr);
> 	pr_alert("printing with pR: %pR\n", ptr);
> }
> 
> static int hello_init(void)
> {
> 	pr_alert("Hello, world\n");
> 
> 	test_printk();
> 
> 	return 0;
> }
> module_init(hello_init);
> 
> static void hello_exit(void)
> {
> 	pr_alert("Goodbye, world\n");
> }
> module_exit(hello_exit);
> 
> MODULE_DESCRIPTION(DRIVER_DESC);
> MODULE_AUTHOR(DRIVER_AUTHOR);
> MODULE_LICENSE("GPL");


Hm, any way to add something like this to the testing infrastructure?
Or maybe just at boot time?  It's nice to keep tests around to ensure
things do not break :)

thanks,

greg k-h