From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1150EC3A59B for ; Fri, 30 Aug 2019 15:12:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5F5023407 for ; Fri, 30 Aug 2019 15:12:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728194AbfH3PMg (ORCPT ); Fri, 30 Aug 2019 11:12:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48628 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727948AbfH3PMg (ORCPT ); Fri, 30 Aug 2019 11:12:36 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 143BB881346; Fri, 30 Aug 2019 15:12:36 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-255.rdu2.redhat.com [10.10.120.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id C4492100197A; Fri, 30 Aug 2019 15:12:34 +0000 (UTC) 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: <20190830145454.B91DF125411@zmta02.collab.prod.int.phx2.redhat.com> References: <20190830145454.B91DF125411@zmta02.collab.prod.int.phx2.redhat.com> <20190830085646.14740-1-hdanton@sina.com> <4384.1567174383@warthog.procyon.org.uk> To: Hillf Danton Cc: dhowells@redhat.com, Sachin Sant , "linuxppc-dev@ozlabs.org" , "keyrings@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: Oops (request_key_auth_describe) while running cve-2016-7042 from LTP MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <11907.1567177954.1@warthog.procyon.org.uk> Date: Fri, 30 Aug 2019 16:12:34 +0100 Message-ID: <11908.1567177954@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.69]); Fri, 30 Aug 2019 15:12:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hillf Danton wrote: > 1, callee has no pre defined duty to help caller in general; they should not > try to do anything, however, to help their callers in principle due to > limited info on their hands IMO. Ah, no. It's entirely reasonable for an API to specify that one of its methods will be called with one or more locks held - and that the method must be aware of this and may make use of this. > 3, no comment can be found in security/keys/request_key_auth.c about > the rcu already documented. There is API documentation in Documentation/security/keys/core.rst. If you look at about line 1538 onwards: * ``void (*describe)(const struct key *key, struct seq_file *p);`` This method is optional. It is called during /proc/keys reading to summarise a key's description and payload in text form. This method will be called with the RCU read lock held. rcu_dereference() should be used to read the payload pointer if the payload is to be accessed. key->datalen cannot be trusted to stay consistent with the contents of the payload. The description will not change, though the key's state may. It is not safe to sleep in this method; the RCU read lock is held by the caller. David