linux-kernel - Re: [PATCH] signals: check_kill_permission: don't check creds if same_thread

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 for Android: free password hash cracker in your pocket

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

Message-Id: <20100520124214.2ac81a21.akpm@linux-foundation.org>
Date:	Thu, 20 May 2010 12:42:14 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Tridgell <tridge@...ba.org>,
	David Howells <dhowells@...hat.com>,
	Eric Paris <eparis@...isplace.org>,
	Jakub Jelinek <jakub@...hat.com>,
	James Morris <jmorris@...ei.org>,
	Roland McGrath <roland@...hat.com>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] signals: check_kill_permission: don't check creds if
 same_thread_group()

On Mon, 17 May 2010 21:54:14 +0200
Oleg Nesterov <oleg@...hat.com> wrote:

> Andrew Tridgell reports that aio_read(SIGEV_SIGNAL) can fail if the
> the notification from the helper thread races with setresuid(), see
> http://samba.org/~tridge/junkcode/aio_uid.c
> 
> This happens because check_kill_permission() doesn't allow to send
> a signal to the task with the different cred->xids. But there is no
> any security reason to check ->cred's when the task sends a signal
> (private or group-wide) to its sub-thread. Whatever we do, any thread
> can bypass all security checks and send SIGKILL to all threads, or
> it can block a signal SIG and do kill(gettid(), SIG) to deliver this
> signal to another sub-thread. Not to mention that CLONE_THREAD implies
> CLONE_VM.
> 
> Change check_kill_permission() to avoid the credentials check when
> the sender and the target are from the same thread group.
> 
> Also, move "cred = current_cred()" down to avoid calling get_current()
> twice.
> 
> Note: David Howells pointed out we could relax this even more, the
> CLONE_SIGHAND (without CLONE_THREAD) case probably does not need
> these checks too.

So... which kernel(s) do we think this fix should be merged into?
--
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/