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=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 CD7AAC43381 for ; Thu, 28 Feb 2019 15:32:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9A4D220C01 for ; Thu, 28 Feb 2019 15:32:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551367946; bh=KEiIZz9xfVnTxdjO3KuNj0QnPOpROjgUVLibf7Lafis=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=XGALCCW5uyY4pUcdr18OZqJD+aL4YFo9v2CU76i9KVUghq82Zydk3NknVBTE5a5nl yNm7/JVm2xFZYxBPIdRPxXkph+8z0av/9qKSR0Plm1XW2SANMtdkGd47L1mIn9kjG1 Xw1CbsM9hUpGEskqyh2bwxlTri88M76TXfNNLkWM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389180AbfB1PcY (ORCPT ); Thu, 28 Feb 2019 10:32:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:34398 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732423AbfB1PcQ (ORCPT ); Thu, 28 Feb 2019 10:32:16 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A1A7F218B0; Thu, 28 Feb 2019 15:32:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551367935; bh=KEiIZz9xfVnTxdjO3KuNj0QnPOpROjgUVLibf7Lafis=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gspTyG7XERiaNULLr7bGpqEa1T8kJ130sR6hH31VbOL43oWxDTnpaHOOmXeiU4nAK nUko47PfLhsQwPaImSWtfbeEYdIUIU8JrJ0iegwI4UVZLORPZxm4l4zELAJlSx3mf5 oegnyLV5oedPNMAeACbeltzWHBUqh+11+io9jTXw= Date: Thu, 28 Feb 2019 16:32:12 +0100 From: Greg Kroah-Hartman To: Paolo Bonzini Cc: Radim =?utf-8?B?S3LEjW3DocWZ?= , Eric Biggers , kvm@vger.kernel.org, syzbot , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, penguin-kernel@i-love.sakura.ne.jp, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: Re: [PATCH] kvm: properly check debugfs dentry before using it Message-ID: <20190228153212.GH8481@kroah.com> References: <0000000000007e10c50580aa7684@google.com> <0000000000006164d205825fb497@google.com> <20190226191932.GB218103@gmail.com> <20190228150805.GA31904@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 28, 2019 at 04:14:50PM +0100, Paolo Bonzini wrote: > On 28/02/19 16:08, Greg Kroah-Hartman wrote: > > debugfs can now report an error code if something went wrong instead of > > just NULL. So if the return value is to be used as a "real" dentry, it > > needs to be checked if it is an error before dereferencing it. > > > > This is now happening because of ff9fb72bc077 ("debugfs: return error > > values, not NULL"). syzbot has found a way to trigger multiple debugfs > > files attempting to be created, which fails, and then the error code > > gets passed to dentry_path_raw() which obviously does not like it. > > > > Reported-by: Eric Biggers > > Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com > > Cc: Paolo Bonzini > > Cc: "Radim Krčmář" > > Cc: kvm@vger.kernel.org > > Signed-off-by: Greg Kroah-Hartman > > > > --- > > > > Paolo, this should be merged into 5.0-final, and if not there, then > > 5.1-rc1 and then backported to 5.0 through the stable tree. If you > > want me to send this to Linus, I will be glad to do so. > > > > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index 585845203db8..076bc38963bf 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -4044,7 +4044,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) > > } > > add_uevent_var(env, "PID=%d", kvm->userspace_pid); > > > > - if (kvm->debugfs_dentry) { > > + if (!IS_ERR_OR_NULL(kvm->debugfs_dentry)) { > > char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL); > > > > if (p) { > > > > Sure, go ahead. > > Acked-by: Paolo Bonzini Wonderful, will do so right now, thanks! greg k-h