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[23.128.96.18]) by mx.google.com with ESMTP id b18si17150971plz.193.2021.10.12.10.32.17; Tue, 12 Oct 2021 10:32:30 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=xmission.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232494AbhJLRdM (ORCPT + 99 others); Tue, 12 Oct 2021 13:33:12 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:55466 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232705AbhJLRdK (ORCPT ); Tue, 12 Oct 2021 13:33:10 -0400 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 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa06.xmission.com X-Spam-Level: X-Spam-Status: No, score=0.2 required=8.0 tests=ALL_TRUSTED,BAYES_05, DCC_CHECK_NEGATIVE,T_TM2_M_HEADER_IN_MSG,T_XMDrugObfuBody_12,XMSubLong autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * -0.5 BAYES_05 BODY: Bayes spam probability is 1 to 5% * [score: 0.0486] * 0.7 XMSubLong Long Subject * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 1.0 T_XMDrugObfuBody_12 obfuscated drug references X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Rune Kleveland X-Spam-Relay-Country: X-Spam-Timing: total 287 ms - load_scoreonly_sql: 0.06 (0.0%), signal_user_changed: 12 (4.3%), b_tie_ro: 11 (3.8%), parse: 1.11 (0.4%), extract_message_metadata: 13 (4.6%), get_uri_detail_list: 1.11 (0.4%), tests_pri_-1000: 5 (1.8%), tests_pri_-950: 1.28 (0.4%), tests_pri_-900: 1.08 (0.4%), tests_pri_-90: 57 (19.9%), check_bayes: 55 (19.3%), b_tokenize: 6 (1.9%), b_tok_get_all: 4.7 (1.6%), b_comp_prob: 1.93 (0.7%), b_tok_touch_all: 40 (13.9%), b_finish: 0.91 (0.3%), tests_pri_0: 174 (60.7%), check_dkim_signature: 0.59 (0.2%), check_dkim_adsp: 3.0 (1.0%), poll_dns_idle: 0.76 (0.3%), tests_pri_10: 2.2 (0.8%), tests_pri_500: 16 (5.5%), rewrite_mail: 0.00 (0.0%) 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) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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