Date: Fri, 19 Feb 2016 14:19:18 -0800 From: Kees Cook <keescook@...omium.org> To: Laura Abbott <labbott@...hat.com> Cc: Laura Abbott <labbott@...oraproject.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCHv2] lkdtm: Add READ_AFTER_FREE test On Fri, Feb 19, 2016 at 2:11 PM, Laura Abbott <labbott@...hat.com> wrote: > On 02/19/2016 11:12 AM, Kees Cook wrote: >> >> On Thu, Feb 18, 2016 at 5:15 PM, Laura Abbott <labbott@...oraproject.org> >> wrote: >>> >>> >>> In a similar manner to WRITE_AFTER_FREE, add a READ_AFTER_FREE >>> test to test free poisoning features. Sample output when >>> no sanitization is present: >>> >>> [ 22.414170] lkdtm: Performing direct entry READ_AFTER_FREE >>> [ 22.415124] lkdtm: Value in memory before free: 12345678 >>> [ 22.415900] lkdtm: Attempting to read from freed memory >>> [ 22.416394] lkdtm: Successfully read value: 12345678 >>> >>> with sanitization: >>> >>> [ 25.874585] lkdtm: Performing direct entry READ_AFTER_FREE >>> [ 25.875527] lkdtm: Value in memory before free: 12345678 >>> [ 25.876382] lkdtm: Attempting to read from freed memory >>> [ 25.876900] general protection fault: 0000 [#1] SMP >>> >>> Signed-off-by: Laura Abbott <labbott@...oraproject.org> >> >> >> Excellent! Could you mention in the changelog which CONFIG (or runtime >> values) will change the lkdtm test? (I thought there was a poisoning >> style that would result in a zero-read instead of a GP?) >> > > There was a zeroing patch in the first draft but given the direction > things are going, I don't see it going in. I'll mention the debug > options which will show this though. Ah! Okay, I was having trouble following what was happening. What's the current state of the use-after-free protections you've been working on? -Kees -- Kees Cook Chrome OS & Brillo Security
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