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 6A452C433EF for ; Thu, 30 Sep 2021 13:06:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F36CE615A2 for ; Thu, 30 Sep 2021 13:06:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org F36CE615A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 5238494009E; Thu, 30 Sep 2021 09:06:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4D2C294003A; Thu, 30 Sep 2021 09:06:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3741B94009E; Thu, 30 Sep 2021 09:06:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0253.hostedemail.com [216.40.44.253]) by kanga.kvack.org (Postfix) with ESMTP id 14BE494003A for ; Thu, 30 Sep 2021 09:06:45 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id C25821822BC4D for ; Thu, 30 Sep 2021 13:06:44 +0000 (UTC) X-FDA: 78644264328.01.309D8CC Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf03.hostedemail.com (Postfix) with ESMTP id 6C3C4300399B for ; Thu, 30 Sep 2021 13:06:44 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 45CAC6126A; Thu, 30 Sep 2021 13:06:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633007203; bh=2E12lxsILybA6TcVpH3Clkx1XYrdgQW3E8uFB2oiPBg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lgdiosn93AauLXFMrr9Usc2pvpe/W79Bk/F24VYCqaajlvOZW38VnA1SHe8Q5ZSSR +k3SeIa2jPtwhRk/pPRUWlUZAStkuID2g1hXF+eOCILkYNcrT6F8tgExarm1azlP59 IWMXzzwDbwBujNxfnprNQQlud94H2E+Bmzn6p3LmfTJuG7yY0eIt98OHAl85+m5PCg luTsXtXHX+um80MmKnbFnREoX1fuqEi2ClAZZ80vQbX5NZHKPJtFHxjEqzojsCMrAZ y67L2Yqv8blaQ8m0lyqaSvs1+3vuj0jv3FxirIFYE4mOx2dQSqgynxx5qXjAKnP1Fh 5VbBl+zV7oh/A== Date: Thu, 30 Sep 2021 15:06:40 +0200 From: Alexey Gladkov To: Jordan Glover Cc: ebiederm@xmission.com, LKML , linux-mm@kvack.org, containers@lists.linux-foundation.org, Yu Zhao Subject: Re: linux 5.14.3: free_user_ns causes NULL pointer dereference Message-ID: <20210930130640.wudkpmn3cmah2cjz@example.org> References: <1M9_d6wrcu6rdPe1ON0_k0lOxJMyyot3KAb1gdyuwzDPC777XVUWPHoTCEVmcK3fYfgu7sIo3PSaLe9KulUdm4TWVuqlbKyYGxRAjsf_Cpk=@protonmail.ch> <87ee9pa6xw.fsf@disp2133> <878rzw77i3.fsf@disp2133> <20210929173611.fo5traia77o63gpw@example.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6C3C4300399B X-Stat-Signature: 4nzm3k9uu8jo5t38rht1ay7mwro6mjyf Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=lgdiosn9; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf03.hostedemail.com: domain of legion@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=legion@kernel.org X-HE-Tag: 1633007204-255366 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000028, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 29, 2021 at 09:39:06PM +0000, Jordan Glover wrote: > > I'm still investigating, but I would like to rule out one option. > > > > Could you check out the patch? > > > Thx, I added it to my kernel and will report in few days. > Does this patch try to fix the issue or make it easier to track? I suspect the error is caused by a race between allow_ucounts() and put_ucounts(). I think this patch could solve the problem. -- Rgrds, legion