full-disclosure - linux bugs (survival stories)?

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Message-ID: <200504122145.j3CLjI0t026676@turing-police.cc.vt.edu>
Date: Tue Apr 12 22:45:34 2005
From: Valdis.Kletnieks at vt.edu (Valdis.Kletnieks@...edu)
Subject: linux bugs (survival stories)? 

On Tue, 12 Apr 2005 21:20:03 -0000, Eduardo Tongson said:

> Stuff like for example circumventing noexec flags on mounted filesystems 
> still is trivial even with the latest and development versions of the
> linux kernel

"like for example" is always a bad way to discuss things, because it's
unclear what exactly you're talking about. ;)

Now, going with specifics...  The last really big "trivial" issue with
bypassing noexec on mounted filesystems was closed by a patch from Ulrich
Drepper in 2.6.0 - basically forcing you to mmap() the binary in and then
mprotect() it to add the exec flag.  And at *that* point, it gets ugly, because
even if you stop them from calling mprotect() to get it executable, they can
still use some variant of "unexec()" (see the Emacs/XEmacs source tree) to dump
it out, twiddle the headers, and then exec() it off some other file system.

So what specific issue with noexec are *you* thinking of, and what is your
proposed fix for it?

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