Re: fix must_not_trace_exec() test

[Chris Wright]

* Andy Lutomirski (luto@xxxxxxxxxxxxx) 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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