Date: Mon, 12 Apr 2004 15:02:52 -0700
From: Chris Wright <chrisw@osdl.org>
To: Andy Lutomirski <luto@myrealbox.com>
Cc: Olaf Dietsche <olaf+list.linux-kernel@olafdietsche.de>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: fix must_not_trace_exec() test
Message-ID: <20040412150252.D21045@build.pdx.osdl.net>
References: <20040410200551.31866667.akpm@osdl.org> <878yh1y1gs.fsf@goat.bogus.local> <407AA51F.5020205@myrealbox.com>
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* Andy Lutomirski (luto@myrealbox.com) wrote:
> Olaf Dietsche wrote:
> > Although, I'd rather not lump together unrelated tests without
> > renaming must_not_trace_exec(). Btw, can someone enlighten me what
> > this atomic_read() test is all about.
> 
> I assumed that the test was to check if the caller is a thread, but that
> sounds odd -- wouldn't it stop being a thread after the exec anyway?
> Maybe that part happens after compute_creds, so this prevents a race?
> Although I don't see how it could be triggered if the thread never
> entered usermode before getting a new fs/files/sighand.

There's no requirement for CLONE_THREAD when using at least CLONE_FS
and CLONE_FILES.  And all of the latter are inherited across execve().
These tests are needed to keep a malicious program from controlling the
setuid program in ways other than ptrace.

thanks,
-chris
-- 
Linux Security Modules     http://lsm.immunix.org     http://lsm.bkbits.net
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