From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-175092-1519307314-2-12214674599678744520 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1519307313; b=F48LZo0YMOo04vEs7QOV2PTdjcJVQf+nLECF6hI3zrkRc50 wCX3MasRt5Phozcj9u54sFaRDPfMpWCQ+IuWFMo+hnNdQxp3laJtdV14rmIvTgYy WC6dbZ4XcWmRYKA+EbXYFNdceyBH4G/sNaojbZxZNLCWshtXlIA7rFnumVTPhCZw SSjFeXvf5OvdKi3YxPWmnG6eRVqxxfVun+xy+C9ucGdGJqtoa9JeunMYHGX1jPev VyTq19yNnQcTE1AoIqLmkQD+WGZhwfo7yumlsc78W1d71x+SXTgy/kTQwR9NnS1N DjKtS8GXw0XDild7/Zc3DggkR6qPw9n3/UrMwFA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1519307313; bh=n1HtRBXa4k+zURa5N/bxP2AHSI oB5Mn23bInl3grk3s=; b=BsxglCBNk2aCF3lr0cNMxhOPHz33MhCfCn7j4R8RED mkwwvoXrCRdpDvkdldbopgCAXIuGCNhIGiXf2yOi/rvJnmEC3ju7hrOg2wbTxYyL k47e6IA3uWSFMoNNBL4ddXOfHb03NJXfy+S6sDOFcbuHwO++tFVhZEZYmlYCyWZQ KSHig4ZP4oFacQ2E5H5B3t7QgbDKlMXYbZWEAc33MTM3qTpg1RGbqPvXvjbUZxCU 8JXRQ8EdWmZuvVoic2Ll+gXjOhia7V1PEgVxBGeTacHGpiGz+J3XIyUB5UazXnLb 9TOoMoQzCuEySXFcZ64ZffNdrM1KXwRIKtg68/PgVwwA== ARC-Authentication-Results: i=1; mx5.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Authentication-Results: mx5.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=linuxfoundation.org; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932516AbeBVNsc (ORCPT ); Thu, 22 Feb 2018 08:48:32 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58920 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932467AbeBVNsb (ORCPT ); Thu, 22 Feb 2018 08:48:31 -0500 Date: Thu, 22 Feb 2018 14:48:32 +0100 From: Greg Kroah-Hartman To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, Todd Kjos , Arve Hjonnevag , Greg Hackmann , stable@vger.kernel.org Subject: Re: [PATCH v2] staging: android: ashmem: Fix lockdep issue during llseek Message-ID: <20180222134832.GA1400@kroah.com> References: <20180216190201.59572-1-joelaf@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180216190201.59572-1-joelaf@google.com> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, Feb 16, 2018 at 11:02:01AM -0800, Joel Fernandes wrote: > ashmem_mutex create a chain of dependencies like so: > > (1) > mmap syscall -> > mmap_sem -> (acquired) > ashmem_mmap > ashmem_mutex (try to acquire) > (block) > > (2) > llseek syscall -> > ashmem_llseek -> > ashmem_mutex -> (acquired) > inode_lock -> > inode->i_rwsem (try to acquire) > (block) > > (3) > getdents -> > iterate_dir -> > inode_lock -> > inode->i_rwsem (acquired) > copy_to_user -> > mmap_sem (try to acquire) > > There is a lock ordering created between mmap_sem and inode->i_rwsem > causing a lockdep splat [2] during a syzcaller test, this patch fixes > the issue by unlocking the mutex earlier. Functionally that's Ok since > we don't need to protect vfs_llseek. > > [1] https://patchwork.kernel.org/patch/10185031/ > [2] https://lkml.org/lkml/2018/1/10/48 > > Cc: Todd Kjos > Cc: Arve Hjonnevag > Cc: Greg Hackmann > Cc: Greg Kroah-Hartman > Cc: stable@vger.kernel.org > Reported-by: syzbot+8ec30bb7bf1a981a2012@syzkaller.appspotmail.com > Signed-off-by: Joel Fernandes > --- > Changes since first version: > Don't relock after vfs call since its not needed. Only reason we lock is > to protect races with asma->file. > https://patchwork.kernel.org/patch/10185031/ I'd like some acks from others before I take this patch. Joel, did the original reporter say this patch solved their issue or not? For some reason I didn't think it worked properly... thanks, greg k-h