linux-kernel - Re: [PATCH] exec: do not leave bprm->interp on stack

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 13 Nov 2012 06:50:11 +0000
From:	halfdog <me@...fdog.net>
To:	Kees Cook <keescook@...omium.org>
CC:	P J P <ppandit@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Josh Triplett <josh@...htriplett.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] exec: do not leave bprm->interp on stack

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Kees Cook wrote:
> On Tue, Nov 6, 2012 at 12:10 AM, P J P <ppandit@...hat.com> wrote:
>> 
>> Hello Kees, Al,
>> 
>> +-- On Sat, 27 Oct 2012, Kees Cook wrote --+ | If we change
>> binfmt_script to not make a recursive call, then we still | need
>> to keep the interp change somewhere off the stack. I still think 
>> | my patchset is the least bad. | | Al, do you have something
>> else in mind?
>> 
>> Guys, are there any updates further?
>> 
>> Al, what's your take on the *rare* extra call to request_module?
> 
> Without any other feedback, I'd like to use my minimal allocation 
> patch, since it fixes the problem and doesn't change any of the 
> semantics of how/when loading happens.

As a first step, I think that we can go with the Keess'
(nice/small/simple) patch. On the long run, exec should be reworked. Not
only interp is modified, also credentials are set, e.g. when using
"ping" as interpreter. With intransparent error handling and
retry-logic, this might be a future local-root-exploit in the beginning
(I tried to, but did not manage yet).


Also a remark from Prasad Pandit did not make it to the list (or at
least I missed the replies).

> Yesterday, while testing Keess' patch I was reading through
> execve(2) manual which says: path name must be a valid executable
> which is NOT a script.
> 
> $ man execve ... Interpreter scripts An interpreter script is a
> text file that has execute permission enabled and whose first line
> is of the form:
> 
> #! interpreter [optional-arg]
> 
> The interpreter must be a valid path name for an executable which
> is not itself a script.

Does someone know what POSIX says about that? I guess that interp
recursion might have some usecases: Script uses interp, but interp was
wrapped by admin or distribution folks into another script to fix
something, e.g. to pass an additional arg.

hd

- -- 
http://www.halfdog.net/
PGP: 156A AE98 B91F 0114 FE88  2BD8 C459 9386 feed a bee
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)

iEYEARECAAYFAlCh7ZEACgkQxFmThv7tq+4X/QCeLN+0qUtP6Hhag1d4iwZ4PZbL
evEAn2iPQH9mJ0zTHMs3qOsaWLRs9UWW
=Ow3u
-----END PGP SIGNATURE-----
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/