From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) by kanga.kvack.org (Postfix) with ESMTP id 661126B7C54 for ; Thu, 6 Dec 2018 16:20:33 -0500 (EST) Received: by mail-qt1-f197.google.com with SMTP id q33so1680555qte.23 for ; Thu, 06 Dec 2018 13:20:33 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j93si950125qtb.131.2018.12.06.13.20.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Dec 2018 13:20:32 -0800 (PST) From: Andrea Arcangeli Subject: [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered Date: Thu, 6 Dec 2018 16:20:28 -0500 Message-Id: <20181206212028.18726-2-aarcange@redhat.com> In-Reply-To: <20181206212028.18726-1-aarcange@redhat.com> References: <20181206212028.18726-1-aarcange@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Mike Rapoport , Mike Kravetz , Jann Horn , Peter Xu , "Dr. David Alan Gilbert" Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd could trigger an harmless false positive WARN_ON. Check the vma is already registered before checking VM_MAYWRITE to shut off the false positive warning. Cc: Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas") Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com Signed-off-by: Andrea Arcangeli --- fs/userfaultfd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index cd58939dc977..7a85e609fc27 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1566,7 +1566,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, cond_resched(); BUG_ON(!vma_can_userfault(vma)); - WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); /* * Nothing to do: this vma is already registered into this @@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, if (!vma->vm_userfaultfd_ctx.ctx) goto skip; + WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); + if (vma->vm_start > start) start = vma->vm_start; vma_end = min(end, vma->vm_end);