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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02594C4332F for ; Tue, 12 Oct 2021 17:31:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 89BD460F23 for ; Tue, 12 Oct 2021 17:31:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 89BD460F23 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id F2C24900003; Tue, 12 Oct 2021 13:31:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EDB93900002; Tue, 12 Oct 2021 13:31:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DCA0A900003; Tue, 12 Oct 2021 13:31:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0053.hostedemail.com [216.40.44.53]) by kanga.kvack.org (Postfix) with ESMTP id CCF2E900002 for ; Tue, 12 Oct 2021 13:31:09 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 7916D181DD416 for ; Tue, 12 Oct 2021 17:31:09 +0000 (UTC) X-FDA: 78688476258.27.CA20E0D Received: from out02.mta.xmission.com (out02.mta.xmission.com [166.70.13.232]) by imf03.hostedemail.com (Postfix) with ESMTP id 0858230000B4 for ; Tue, 12 Oct 2021 17:31:08 +0000 (UTC) Received: from in02.mta.xmission.com ([166.70.13.52]:51984) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1maLcJ-00Ca0L-CA; Tue, 12 Oct 2021 11:31:07 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95]:60918 helo=email.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1maLcI-00Gtkd-Gi; Tue, 12 Oct 2021 11:31:06 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Rune Kleveland Cc: Yu Zhao , Alexey Gladkov , Jordan Glover , LKML , linux-mm@kvack.org, containers@lists.linux-foundation.org References: <1M9_d6wrcu6rdPe1ON0_k0lOxJMyyot3KAb1gdyuwzDPC777XVUWPHoTCEVmcK3fYfgu7sIo3PSaLe9KulUdm4TWVuqlbKyYGxRAjsf_Cpk=@protonmail.ch> <87ee9pa6xw.fsf@disp2133> <878rzw77i3.fsf@disp2133> <20210929173611.fo5traia77o63gpw@example.org> <20210930130640.wudkpmn3cmah2cjz@example.org> <878rz8wwb6.fsf@disp2133> <87v92cvhbf.fsf@disp2133> Date: Tue, 12 Oct 2021 12:31:00 -0500 In-Reply-To: (Rune Kleveland's message of "Sun, 10 Oct 2021 10:59:10 +0200") Message-ID: <87o87u2lrf.fsf@disp2133> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1maLcI-00Gtkd-Gi;;;mid=<87o87u2lrf.fsf@disp2133>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/mi8WNgfr/F/tuuyDRQWaOtXEfsPIVixM= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: linux 5.14.3: free_user_ns causes NULL pointer dereference X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Authentication-Results: imf03.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=xmission.com; spf=pass (imf03.hostedemail.com: domain of ebiederm@xmission.com designates 166.70.13.232 as permitted sender) smtp.mailfrom=ebiederm@xmission.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0858230000B4 X-Stat-Signature: yumbjxkw5p46gqgt6tdyn5m44dqtnzjf X-HE-Tag: 1634059868-659623 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Rune Kleveland writes: > Hi! > > Just wanted to let you know that I still get these on stock Fedora kernel > 5.14.10 on the IBM blades. But it took 10 hours before the first server > crashed. The other 4 still runs fine since 15 hours ago. So for me it seems more > stable now, but that could just be a coincidence. Alex and I have been working on this and we are still tracking down whatever is going on. While we haven't found the issue yet we have found a trivially correct change that allows us to reproduce the issue faster. Hopefully this will allow us to narrow down on whatever it is soon. diff --git a/kernel/ucount.c b/kernel/ucount.c index bb51849e6375..3b7e176cf7a2 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -203,6 +203,7 @@ void put_ucounts(struct ucounts *ucounts) if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) { hlist_del_init(&ucounts->node); + ucounts->ns = NULL; spin_unlock_irqrestore(&ucounts_lock, flags); kfree(ucounts); } Eric