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 2BD53C3A59B for ; Fri, 30 Aug 2019 14:13:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0904823427 for ; Fri, 30 Aug 2019 14:13:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727984AbfH3ONG (ORCPT ); Fri, 30 Aug 2019 10:13:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61352 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727914AbfH3ONF (ORCPT ); Fri, 30 Aug 2019 10:13:05 -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 617ED308620B; Fri, 30 Aug 2019 14:13:05 +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 125E11001925; Fri, 30 Aug 2019 14:13:03 +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: <20190830085646.14740-1-hdanton@sina.com> References: <20190830085646.14740-1-hdanton@sina.com> 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: <4383.1567174383.1@warthog.procyon.org.uk> Date: Fri, 30 Aug 2019 15:13:03 +0100 Message-ID: <4384.1567174383@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-4.5.16 (mx1.redhat.com [10.5.110.42]); Fri, 30 Aug 2019 14:13:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hillf Danton wrote: > - struct request_key_auth *rka = dereference_key_rcu(key); > + struct request_key_auth *rka; > + > + rcu_read_lock(); > + rka = dereference_key_rcu(key); This shouldn't help as the caller, proc_keys_show(), is holding the RCU read lock across the call. The end of the function reads: if (key->type->describe) key->type->describe(key, m); seq_putc(m, '\n'); rcu_read_unlock(); return 0; } and the documentation says "This method will be called with the RCU read lock held". I suspect the actual bugfix is this bit: > + if (!rka) > + goto out; David