linux-kernel - Re: [PATCH] KEYS: close race between key lookup and freeing

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Message-ID: <30932.1420473588@warthog.procyon.org.uk>
Date:	Mon, 05 Jan 2015 15:59:48 +0000
From:	David Howells <dhowells@...hat.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	keyrings@...ux-nfs.org (open list:KEYS/KEYRINGS:),
	linux-security-module@...r.kernel.org (open list:SECURITY SUBSYSTEM)
Subject: Re: [PATCH] KEYS: close race between key lookup and freeing

Sasha Levin <sasha.levin@...cle.com> wrote:

> When a key is being garbage collected, it's key->user would get put before
> the ->destroy() callback is called, where the key is removed from it's
> respective tracking structures.
> 
> This leaves a key hanging in a semi-invalid state which leaves a window open
> for a different task to try an access key->user. An example is
> find_keyring_by_name() which would dereference key->user for a key that is
> in the process of being garbage collected (where key->user was freed but
> ->destroy() wasn't called yet - so it's still present in the linked list).
> 
> This would cause either a panic, or corrupt memory.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>

Applied.
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