From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754104AbcG1KHU (ORCPT ); Thu, 28 Jul 2016 06:07:20 -0400 Received: from smtp-2.httrack.com ([195.154.67.106]:57815 "EHLO smtp-2.httrack.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752056AbcG1KHP (ORCPT ); Thu, 28 Jul 2016 06:07:15 -0400 X-Greylist: delayed 1035 seconds by postgrey-1.27 at vger.kernel.org; Thu, 28 Jul 2016 06:07:15 EDT X-Spam-Filter: check_local@smtp-2.httrack.com by digitalanswers.org Date: Thu, 28 Jul 2016 11:49:47 +0200 (CEST) From: Xavier Roche X-X-Sender: rocheml@proliant.localnet To: LKML Subject: Question on page length clamping in hash walk fix and syscall crashes Message-ID: User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII X-Greylist: Default is to whitelist mail, not delayed by milter-greylist-4.3.9 (smtp-2.httrack.com [IPv6:2001:bc8:30e2::1]); Thu, 28 Jul 2016 11:49:57 +0200 (CEST) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.11 (smtp-1.httrack.com [192.168.1.250]); Thu, 28 Jul 2016 11:49:47 +0200 (CEST) X-SPF-Scan-By: smf-spf v2.0.2 - http://smfs.sf.net/ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi folks, We stumble upon an issue while using an AF_ALG socket to compute a hash (crc32) directly in the kernel (using splice magic) The issue has been fixed AFAICS by Herbert Xu in cc440a5b68873b7b98c3130d09a69a1b13acb0b7 in a rather isolated patch (three lines diff) I could validate that the patch does indeed fix the issue we were having. This bug seems to be more than a computation issue, as we experienced weird crashes in random syscall when it is triggered (ie. unpatched), such as fork, or futex-related primitives (!). The issue can be reproduced with this standalone program: https://bitbucket.org/scality/xavier-sandbox-public/raw/HEAD/kernel/issues/splicertest.c Most up-to-date stable distro are using the buggy version (Centos 7: 3.10.0, Ubuntu trusty: 3.13.0, Fedora 22: 4.3.6, etc.) Question: is the weird behavior observed (crashes inside kernel) "normal" w.r.t this issue, and how cherry-pick policy is organized w.r.t older kernel releases (LTS only ?) [ Typically the bug does not appear in 3.14.70, 3.16.0, 3.19.0 or 4.2.0 ] And sorry in advance if this question has already been answered, but I could not find any clear hint.