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Date: Wed, 15 Apr 2015 15:14:33 -0700
From: Tavis Ormandy <taviso@...gle.com>
To: oss-security@...ts.openwall.com
Subject: Re: Re: Problems in automatic crash analysis frameworks
On Wed, Apr 15, 2015 at 1:44 PM, Tavis Ormandy <taviso@...gle.com> wrote:
> On Wed, Apr 15, 2015 at 2:45 AM, Jakub Filak <jfilak@...hat.com> wrote:
>> Hello,
>>
>> I have a question regarding the ABRT vulnerabilities. I don't particularly understand how an attacker can use /proc/pid/exe symlink to force ABRT to read an arbitrary file if the symlink cannot be changed and kernel refuses to create the process if the symlink's target is not executable.
>>
>>> This code trusts the /proc/pid/exe symlink, even though it is possible
>>> to link it anywhere you want.
>>>
>>> https://github.com/abrt/abrt/blob/master/src/hooks/abrt-hook-ccpp.c#L368
>>>
>>> sprintf(buf, "/proc/%lu/exe", (long)pid);
>>> int src_fd_binary = open(buf, O_RDONLY); /* might fail and
>>> return -1, it's ok */
>>
>> Thank you for clarifying this for me.
>>
>
> My description was incorrect, It can't be an arbitrary file, just a
> file you have execute but not read permission.
>
> Tavis.
Apparently I'm wrong again, spender points out it may still be possible.
https://twitter.com/grsecurity/status/588459661805817858
Tavis.
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