linux-kernel - Re: execve-under-ptrace API bug (was Re: Ptrace documentation, draft #3)

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]

Message-ID: <20110530135623.GC4739@redhat.com>
Date:	Mon, 30 May 2011 15:56:23 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>,
	jan.kratochvil@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	indan@....nu
Subject: Re: execve-under-ptrace API bug (was Re: Ptrace documentation,
	draft #3)

On 05/30, Tejun Heo wrote:
>
> A problem is that by the time de-threading is in progress, it's
> already too deep and there's no way back and the exec'ing thread has
> to wait for completion in uninterruptible sleeps - ie. it expects
> de-threading to finish in finite amount of time and to achieve that it
> basically sends SIGKILL to all other threads.  If we introduce a trap
> in de-threading itself, we can easily end up with an unkillable
> task.

"unkillable" is not the problem, afaics. But the new trap is problematic,
we do not want the TASK_TRACED task holding the mutexes taken by the
callers of de_thread.

> 1. Don't allow more than one thread in the same group enter exec(2)
>    path at all.

This is already done, see do_execve()->prepare_bprm_creds().
cred_guard_mutex serializes exec. Btw, probably this allows us to do
more cleanups/simplifications in do_execve() paths.

> 2. Add another trap point right before de-threading commences.

See above.

Oleg.

--
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/