From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 18 Jul 2018 10:12:31 +0300 From: Mike Rapoport To: Eric Biggers Cc: Andrea Arcangeli , syzbot , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: Re: kernel BUG at fs/userfaultfd.c:LINE! (2) References: <000000000000dcb1a1057112c66a@google.com> <20180717192806.GI75957@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180717192806.GI75957@gmail.com> Message-Id: <20180718071230.GA4302@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: On Tue, Jul 17, 2018 at 12:28:06PM -0700, Eric Biggers wrote: > [+Cc userfaultfd developers and linux-mm] > > The reproducer hits the BUG_ON() in userfaultfd_release(): > > BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ > !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); Thanks for the CC. The fix is below. -- Sincerely yours, Mike. >>From 3711b6a72abe3796b2b97fdba8eadd995b29f195 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Wed, 18 Jul 2018 09:45:54 +0300 Subject: [PATCH] userfaultfd: remove uffd flags from vma->vm_flags if UFFD_EVENT_FORK fails The fix in commit 0cbb4b4f4c44 ("userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails") cleared the vma->vm_userfaultfd_ctx but kept userfaultfd flags in vma->vm_flags that were copied from the parent process VMA. As the result, there is an inconsistency between the values of vma->vm_userfaultfd_ctx.ctx and vma->vm_flags which triggers BUG_ON in userfaultfd_release(). Clearing the uffd flags from vma->vm_flags in case of UFFD_EVENT_FORK failure resolves the issue. Signed-off-by: Mike Rapoport Reported-by: syzbot+121be635a7a35ddb7dcb@syzkaller.appspotmail.com Cc: Andrea Arcangeli Cc: Eric Biggers Cc: stable@vger.kernel.org --- fs/userfaultfd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 594d192b2331..bad9cea37f12 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -633,8 +633,10 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, /* the various vma->vm_userfaultfd_ctx still points to it */ down_write(&mm->mmap_sem); for (vma = mm->mmap; vma; vma = vma->vm_next) - if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) + if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; + vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); + } up_write(&mm->mmap_sem); userfaultfd_ctx_put(release_new_ctx); -- 2.7.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id 7BDA46B0003 for ; Wed, 18 Jul 2018 03:12:43 -0400 (EDT) Received: by mail-oi0-f71.google.com with SMTP id e23-v6so3439726oii.10 for ; Wed, 18 Jul 2018 00:12:43 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id t187-v6si1812131oie.262.2018.07.18.00.12.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 18 Jul 2018 00:12:42 -0700 (PDT) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6I78df4031217 for ; Wed, 18 Jul 2018 03:12:41 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ka03k21ky-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 18 Jul 2018 03:12:41 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 18 Jul 2018 08:12:38 +0100 Date: Wed, 18 Jul 2018 10:12:31 +0300 From: Mike Rapoport Subject: Re: kernel BUG at fs/userfaultfd.c:LINE! (2) References: <000000000000dcb1a1057112c66a@google.com> <20180717192806.GI75957@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180717192806.GI75957@gmail.com> Message-Id: <20180718071230.GA4302@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Eric Biggers Cc: Andrea Arcangeli , syzbot , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk On Tue, Jul 17, 2018 at 12:28:06PM -0700, Eric Biggers wrote: > [+Cc userfaultfd developers and linux-mm] > > The reproducer hits the BUG_ON() in userfaultfd_release(): > > BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ > !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); Thanks for the CC. The fix is below. -- Sincerely yours, Mike. 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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 38E1EECDFB8 for ; Wed, 18 Jul 2018 07:12:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD32C2084E for ; Wed, 18 Jul 2018 07:12:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DD32C2084E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726953AbeGRHtG (ORCPT ); Wed, 18 Jul 2018 03:49:06 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:53106 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726276AbeGRHtF (ORCPT ); Wed, 18 Jul 2018 03:49:05 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6I78eEL073478 for ; Wed, 18 Jul 2018 03:12:41 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ka0hxh0vv-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 18 Jul 2018 03:12:41 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 18 Jul 2018 08:12:34 +0100 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w6I7CXLj27590852 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 18 Jul 2018 07:12:33 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BE18842045; Wed, 18 Jul 2018 10:12:51 +0100 (BST) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 253884204D; Wed, 18 Jul 2018 10:12:51 +0100 (BST) Received: from rapoport-lnx (unknown [9.148.8.216]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Wed, 18 Jul 2018 10:12:51 +0100 (BST) Date: Wed, 18 Jul 2018 10:12:31 +0300 From: Mike Rapoport To: Eric Biggers Cc: Andrea Arcangeli , syzbot , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: Re: kernel BUG at fs/userfaultfd.c:LINE! (2) References: <000000000000dcb1a1057112c66a@google.com> <20180717192806.GI75957@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180717192806.GI75957@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 18071807-0008-0000-0000-000002547029 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18071807-0009-0000-0000-000021BAC50C Message-Id: <20180718071230.GA4302@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-18_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=869 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807180084 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 17, 2018 at 12:28:06PM -0700, Eric Biggers wrote: > [+Cc userfaultfd developers and linux-mm] > > The reproducer hits the BUG_ON() in userfaultfd_release(): > > BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ > !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); Thanks for the CC. The fix is below. -- Sincerely yours, Mike. >From 3711b6a72abe3796b2b97fdba8eadd995b29f195 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Wed, 18 Jul 2018 09:45:54 +0300 Subject: [PATCH] userfaultfd: remove uffd flags from vma->vm_flags if UFFD_EVENT_FORK fails The fix in commit 0cbb4b4f4c44 ("userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails") cleared the vma->vm_userfaultfd_ctx but kept userfaultfd flags in vma->vm_flags that were copied from the parent process VMA. As the result, there is an inconsistency between the values of vma->vm_userfaultfd_ctx.ctx and vma->vm_flags which triggers BUG_ON in userfaultfd_release(). Clearing the uffd flags from vma->vm_flags in case of UFFD_EVENT_FORK failure resolves the issue. Signed-off-by: Mike Rapoport Reported-by: syzbot+121be635a7a35ddb7dcb@syzkaller.appspotmail.com Cc: Andrea Arcangeli Cc: Eric Biggers Cc: stable@vger.kernel.org --- fs/userfaultfd.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 594d192b2331..bad9cea37f12 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -633,8 +633,10 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, /* the various vma->vm_userfaultfd_ctx still points to it */ down_write(&mm->mmap_sem); for (vma = mm->mmap; vma; vma = vma->vm_next) - if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) + if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; + vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); + } up_write(&mm->mmap_sem); userfaultfd_ctx_put(release_new_ctx); -- 2.7.4