linux-kernel - Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call filtering

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Date:	Thu, 26 May 2011 11:34:16 -0700 (PDT)
From:	david@...g.hm
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Will Drewry <wad@...omium.org>, Colin Walters <walters@...bum.org>,
	Kees Cook <kees.cook@...onical.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call
 filtering

On Thu, 26 May 2011, Linus Torvalds wrote:
> 
> On Thu, May 26, 2011 at 9:33 AM, Will Drewry <wad@...omium.org> wrote:
>>
>> FWIW, none of the patches deal with privilege escalation via setuid
>> files or file capabilities.
>
> That is NOT AT ALL what I'm talking about.
>
> I'm talking about the "setuid()" system call (and all its cousins:
> setgit/setreuid etc). And the whole thread has been about filtering
> system calls, no?
>
> Do a google code search for setuid.
>
> In good code, it will look something like
>
>  uid = getuid();
>
>  if (setuid(uid)) {
>    fprintf(stderr, "Unable to drop provileges\n");
>    exit(1);
>  }
>
> but I guarantee you that there are cases where people just blindly
> drop privileges. google code search found me at least the "heirloom"
> source code doing exactly that.

I believe that sendmail had this exact vunerability when capibilities were 
used to control setuid a couple of years ago.

David Lang
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