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=-0.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, FREEMAIL_REPLYTO_END_DIGIT,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 1F76DC433EF for ; Wed, 15 Sep 2021 22:42:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B24C160FC0 for ; Wed, 15 Sep 2021 22:42:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B24C160FC0 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=protonmail.ch Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id EADAD900002; Wed, 15 Sep 2021 18:42:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E5CF16B0072; Wed, 15 Sep 2021 18:42:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D73AC900002; Wed, 15 Sep 2021 18:42:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0217.hostedemail.com [216.40.44.217]) by kanga.kvack.org (Postfix) with ESMTP id C8BC16B0071 for ; Wed, 15 Sep 2021 18:42:24 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 7197F181286FE for ; Wed, 15 Sep 2021 22:42:24 +0000 (UTC) X-FDA: 78591283008.22.7B091F8 Received: from mail-40138.protonmail.ch (mail-40138.protonmail.ch [185.70.40.138]) by imf28.hostedemail.com (Postfix) with ESMTP id E1C4B90000A2 for ; Wed, 15 Sep 2021 22:42:23 +0000 (UTC) Date: Wed, 15 Sep 2021 22:42:21 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.ch; s=protonmail; t=1631745741; bh=pAmIuVPKbq7xlzn31sYFI/isG8w/U8GGJ4v5onsDWC0=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=DLhldFRJ8CsC+qiaP/levzeqkXdIldnUige1c/rUeEs+mbNAD7D2usbL/xdw7Vmav OfWiLThJheIqdmVNyjS21r+Wj6MtQzoEUd0JmWBrInbQvnk1K3L3evHzSI9vcTC6Om VixLfArB7cNLJBWylpcE7lSqXoQNZOKPtT+qkzIM= To: ebiederm@xmission.com From: Jordan Glover Cc: LKML , "linux-mm\\@kvack.org" , "legion\\@kernel.org" , "containers\\@lists.linux-foundation.org" Reply-To: Jordan Glover Subject: Re: linux 5.14.3: free_user_ns causes NULL pointer dereference Message-ID: In-Reply-To: <87ee9pa6xw.fsf@disp2133> References: <1M9_d6wrcu6rdPe1ON0_k0lOxJMyyot3KAb1gdyuwzDPC777XVUWPHoTCEVmcK3fYfgu7sIo3PSaLe9KulUdm4TWVuqlbKyYGxRAjsf_Cpk=@protonmail.ch> <87ee9pa6xw.fsf@disp2133> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=protonmail.ch header.s=protonmail header.b=DLhldFRJ; spf=pass (imf28.hostedemail.com: domain of Golden_Miller83@protonmail.ch designates 185.70.40.138 as permitted sender) smtp.mailfrom=Golden_Miller83@protonmail.ch; dmarc=pass (policy=quarantine) header.from=protonmail.ch X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E1C4B90000A2 X-Stat-Signature: gdgy4hhjqkmbm18n8auymibxbfns11nj X-HE-Tag: 1631745743-161982 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: On Wednesday, September 15th, 2021 at 9:02 PM, wrot= e: > Jordan Glover Golden_Miller83@protonmail.ch writes: > > > Hi, recently I hit system freeze after I was closing few containerized = apps on my system. As for now it occurred only once on linux 5.14.3. I thin= k it maybe be related to "Count rlimits in each user namespace" patchset me= rged during 5.14 window > > > > https://lore.kernel.org/all/257aa5fb1a7d81cf0f4c34f39ada2320c4284771.16= 19094428.git.legion@kernel.org/T/#u > > So that warning comes from: > > void dec_ucount(struct ucounts *ucounts, enum ucount_type type) > > { > > struct ucounts *iter; > > for (iter =3D ucounts; iter; iter =3D iter->ns->ucounts) { > > =09long dec =3D atomic_long_dec_if_positive(&iter->ucount[type]); > > =09WARN_ON_ONCE(dec < 0); > } > put_ucounts(ucounts); > > > } > > Which certainly looks like a reference count bug. It could also be a > > memory stomp somewhere close. > > Do you have any idea what else was going on? This location is the > > symptom but not the actual cause. > > Eric I had about 2 containerized (flatpak/bubblewrap) apps (browser + music play= er) running . I quickly closed them with intent to shutdown the system but = instead get the freeze and had to use magic sysrq to reboot. System logs en= d with what I posted and before there is nothing suspicious. Maybe it's some random fluke. I'll reply if I hit it again. Jordan