oss-security - Re: CVE request - kernel: DoS on x86

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Date: Thu, 18 Feb 2010 10:23:36 +0800
From: Eugene Teo <eugene@...hat.com>
To: oss-security@...ts.openwall.com
CC: dann frazier <dannf@...nf.org>,
        "Steven M. Christey" <coley@...us.mitre.org>
Subject: Re: CVE request - kernel: DoS on x86_64

On 02/05/2010 06:46 AM, dann frazier wrote:
> On Thu, Feb 04, 2010 at 01:09:09PM +0800, Eugene Teo wrote:
>> On 02/04/2010 10:28 AM, dann frazier wrote:
>>> On Mon, Feb 01, 2010 at 01:09:12PM +0800, Eugene Teo wrote:
>>>> Reported by Mathias Krause. The problem seams to be located in
>>>> fs/binfmt_elf.c:load_elf_binary(). It calls SET_PERSONALITY() prior
>>>> checking that the ELF interpreter is available. This in turn makes the
>>>> previously 32 bit process a 64 bit one which would be fine if execve()
>>>> would succeed. But after the SET_PERSONALITY() the open_exec() call
>>>> fails (because it cannot find the interpreter) and execve() almost
>>>> instantly returns with an error. If you now look at /proc/PID/maps
>>>> you'll see, that it has the vsyscall page mapped which shouldn't be. But
>>>> the process is not dead yet, it's still running. By now generating a
>>>> segmentation fault and in turn trying to generate a core dump the
>>>> kernel just dies.
>>>>
>>>> Steps to Reproduce:
>>>> 1. Enable core dumps
>>>> 2. Start an 32 bit program that tries to execve() an 64 bit program
>>>> 3. The 64 bit program cannot be started by the kernel because it can't
>>>> find the interpreter, i.e. execve returns with an error
>>>> 4. Generate a segmentation fault
>>>> 5. panic
>>>>
>>>> Upstream commit:
>>>> http://git.kernel.org/linus/221af7f87b97431e3ee21ce4b0e77d5411cf1549
>>>
>>> Thanks Eugene.
>>>
>>> Also note this fix for a regression in the above:
>>>     http://git.kernel.org/linus/7ab02af428c2d312c0cf8fb0b01cc1eb21131a3d
>>
>> Ben Hutchings reported (via stable review list) that the fix did not
>> work for him. Will monitor the list if there are other follow-ups.
>
> Indeed, it also needs this change for x86:
>   http://git.kernel.org/linus/05d43ed8a89c159ff641d472f970e3f1baa66318
>
> And the corresponding changes for powerpc&  sparc:
>   http://git.kernel.org/linus/94f28da8409c6059135e89ac64a0839993124155
>   http://git.kernel.org/linus/94673e968cbcce07fa78dac4b0ae05d24b5816e1
>
> All are in queue-2.6.32 now, btw.

Here's my updated list of patches to backport for this vulnerability:
  - 221af7f87 ("Split 'flush_old_exec' into two functions")
  - 05d43ed8a ("x86: get rid of the insane TIF_ABI_PENDING bit")
  - 7ab02af42 ("Fix 'flush_old_exec()/setup_new_exec()' split")
  - 94f28da84 ("powerpc: TIF_ABI_PENDING bit removal")
  - 1252f238d ("x86: set_personality_ia32() misses force_personality32")

Thanks, Eugene
-- 
Eugene Teo / Red Hat Security Response Team

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