linux-kernel - Re: [PATCH 1/1] cred: copy_process() should clear child->replacement_session

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Message-ID: <14057.1334141269@redhat.com>
Date:	Wed, 11 Apr 2012 11:47:49 +0100
From:	David Howells <dhowells@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] cred: copy_process() should clear child->replacement_session_keyring

Oleg Nesterov <oleg@...hat.com> wrote:

> keyctl_session_to_parent(task) sets ->replacement_session_keyring,
> it should be processed and cleared by key_replace_session_keyring().
> 
> However, this task can fork before it notices TIF_NOTIFY_RESUME and
> the new child gets the bogus ->replacement_session_keyring copied by
> dup_task_struct(). This is obviously wrong and, if nothing else, this
> leads to put_cred(already_freed_cred).
> 
> change copy_creds() to clear this member. If copy_process() fails
> before this point the wrong ->replacement_session_keyring doesn't
> matter, exit_creds() won't be called.
> 
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: David Howells <dhowells@...hat.com>
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