Re: [PATCH] [SECURITY] suid procs exec'd with bad 0,1,2 fds

Zachary Amsden (amsdenz@aavid.com)
Mon, 3 Aug 1998 13:18:07 -0400

-----Original Message-----
From: David S. Miller <davem@dm.cobaltmicro.com>
To: amsdenz@aavid.com <amsdenz@aavid.com>
Cc: sstone@ume.pht.co.jp <sstone@ume.pht.co.jp>; alan@lxorguk.ukuu.org.uk
<alan@lxorguk.ukuu.org.uk>; torvalds@transmeta.com <torvalds@transmeta.com>;
linux-kernel@vger.rutgers.edu <linux-kernel@vger.rutgers.edu>
Date: Monday, August 03, 1998 12:26 PM
Subject: Re: [PATCH] [SECURITY] suid procs exec'd with bad 0,1,2 fds

>
>What if a root process wants to put a suid program at the end of a
>shell pipeline for example? This changes core unix semantics, and is
>a bandaid at best.

So it runs an suid program at the end of a pipeline...

The only cases where execution is denied are when there is an ID
change i.e. UID 172->4 and one of fds 0,1,2 is missing or is set
to close on exec.

No root call to exec will ever fail with EPERM.

If a user wants to put an suid program at the end of a pipeline,
they do. They just better make sure that the pipeline is complete,
i.e. no missing stdin/stdout/stderr.

Zachary Amsden
amsden@andrew.cmu.edu

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