linux-kernel - Re: [PATCHv2] lkdtm: Add READ_AFTER

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Message-ID: <56CDFD8A.1040000@redhat.com>
Date:	Wed, 24 Feb 2016 10:59:22 -0800
From:	Laura Abbott <labbott@...hat.com>
To:	Kees Cook <keescook@...omium.org>
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 02/23/2016 02:37 PM, Kees Cook wrote:
> On Tue, Feb 23, 2016 at 1:25 PM, Kees Cook <keescook@...omium.org> wrote:
>
>> zero poison only:
>> DEBUG_PAGEALLOC=n
>> PAGE_POISONING=y
>> PAGE_POISONING_NO_SANITY=y
>> PAGE_POISONING_ZERO=y
>> page_poison=on
>
> This combo (in next-20160223) results in an unusable system. :(
>
> [    1.754183] random: init urandom read with 11 bits of entropy available
> [    1.768449] hostname (1171) used greatest stack depth: 11808 bytes left
> [    1.787954] BUG: Bad page map in process init  pte:3d656c6f736e6f63
> pmd:00020067
> [    1.789177] addr:00007f9f68200000 vm_flags:00000070 anon_vma:
>     (null) mapping:ffff88007c314058 index:141
> [    1.790564] file:libdl-2.19.so fault:ext4_filemap_fault
> mmap:ext4_file_mmap readpage:ext4_readpage
>
> -Kees
>

Hmmm, it looks like the -mm tree currently only has the v1 of the
poisoning patches and not the v2. The v1 had a bug which would
cause issues like this due to some pages not getting zeroed fully. I should
follow up on that today.

Thanks,
Laura