From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759187Ab2CSPjO (ORCPT ); Mon, 19 Mar 2012 11:39:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7367 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755519Ab2CSPjM (ORCPT ); Mon, 19 Mar 2012 11:39:12 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20120319104432.56fe1e66@redhat.com> References: <20120319104432.56fe1e66@redhat.com> <20120208110254.4050.8856.stgit@warthog.procyon.org.uk> <20120208110400.4050.11565.stgit@warthog.procyon.org.uk> To: Jeff Layton Cc: dhowells@redhat.com, steved@redhat.com, jmorris@namei.org, linux-security-module@vger.kernel.org, keyrings@linux-nfs.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [Keyrings] [PATCH 7/9] KEYS: Permit in-place link replacement in keyring list Date: Mon, 19 Mar 2012 15:39:00 +0000 Message-ID: <14790.1332171540@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jeff Layton wrote: > Why is it safe to use key_put(rcu_access_pointer(...)) ? Clearly that > pointer will end up being dereferenced, right? Simple. This key_put() is called from within keyring_destroy() and that is only ever called from the garbage collector - which is non-reentrant. Add to that that key_put() never actually destroys a now-unused key, but merely schedules the gc for a future run, and it's *that* that searches out unused keys and deletes them. David