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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 3293FC55186 for ; Wed, 22 Apr 2020 10:39:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F86220656 for ; Wed, 22 Apr 2020 10:39:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587551993; bh=SN/5j2Okkn1eVrwRTaxVF3OLAi+cty+PbHxBtT3BDG8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=R+o/ZbM5k8FKs/sRvftQM/ExknGcEg/Mxaj5EqFn8DlVmwKO1biVy3RvDswj4hHyE SQjwlqilLO/wf8i930ObcoXIFuBRU6PdulKsg28YtMl7xEYBAkZvdO44T6LMIO3w0a 0QvsCVVAJGJFrtK5YCMKF0BJruPzrDEND3oeNY04= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730191AbgDVKjw (ORCPT ); Wed, 22 Apr 2020 06:39:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:57346 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730161AbgDVKVR (ORCPT ); Wed, 22 Apr 2020 06:21:17 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.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 26B312076B; Wed, 22 Apr 2020 10:21:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587550876; bh=SN/5j2Okkn1eVrwRTaxVF3OLAi+cty+PbHxBtT3BDG8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WWNejAhca18lcqwuOGeh4ZCU26fk49NsQE8Gtz+2v3BbFzyM+HzYKEJXmk5kmH8dj McQEWU9gDl2FxjDG17hQUXKtfZbTEXBNYIwS5aCwQZYnuMVsR7YUr3Ci2Oms0/OHRZ nWPPVGnNj7/zOklXjYW+ujpF3ZnpwFqN1/xGSRWI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Andrii Nakryiko , Daniel Borkmann Subject: [PATCH 5.6 011/166] bpf: Prevent re-mmap()ing BPF map as writable for initially r/o mapping Date: Wed, 22 Apr 2020 11:55:38 +0200 Message-Id: <20200422095049.430771557@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200422095047.669225321@linuxfoundation.org> References: <20200422095047.669225321@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrii Nakryiko commit 1f6cb19be2e231fe092f40decb71f066eba090d7 upstream. VM_MAYWRITE flag during initial memory mapping determines if already mmap()'ed pages can be later remapped as writable ones through mprotect() call. To prevent user application to rewrite contents of memory-mapped as read-only and subsequently frozen BPF map, remove VM_MAYWRITE flag completely on initially read-only mapping. Alternatively, we could treat any memory-mapping on unfrozen map as writable and bump writecnt instead. But there is little legitimate reason to map BPF map as read-only and then re-mmap() it as writable through mprotect(), instead of just mmap()'ing it as read/write from the very beginning. Also, at the suggestion of Jann Horn, drop unnecessary refcounting in mmap operations. We can just rely on VMA holding reference to BPF map's file properly. Fixes: fc9702273e2e ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY") Reported-by: Jann Horn Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Reviewed-by: Jann Horn Link: https://lore.kernel.org/bpf/20200410202613.3679837-1-andriin@fb.com Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/syscall.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -592,9 +592,7 @@ static void bpf_map_mmap_open(struct vm_ { struct bpf_map *map = vma->vm_file->private_data; - bpf_map_inc_with_uref(map); - - if (vma->vm_flags & VM_WRITE) { + if (vma->vm_flags & VM_MAYWRITE) { mutex_lock(&map->freeze_mutex); map->writecnt++; mutex_unlock(&map->freeze_mutex); @@ -606,13 +604,11 @@ static void bpf_map_mmap_close(struct vm { struct bpf_map *map = vma->vm_file->private_data; - if (vma->vm_flags & VM_WRITE) { + if (vma->vm_flags & VM_MAYWRITE) { mutex_lock(&map->freeze_mutex); map->writecnt--; mutex_unlock(&map->freeze_mutex); } - - bpf_map_put_with_uref(map); } static const struct vm_operations_struct bpf_map_default_vmops = { @@ -641,14 +637,16 @@ static int bpf_map_mmap(struct file *fil /* set default open/close callbacks */ vma->vm_ops = &bpf_map_default_vmops; vma->vm_private_data = map; + vma->vm_flags &= ~VM_MAYEXEC; + if (!(vma->vm_flags & VM_WRITE)) + /* disallow re-mapping with PROT_WRITE */ + vma->vm_flags &= ~VM_MAYWRITE; err = map->ops->map_mmap(map, vma); if (err) goto out; - bpf_map_inc_with_uref(map); - - if (vma->vm_flags & VM_WRITE) + if (vma->vm_flags & VM_MAYWRITE) map->writecnt++; out: mutex_unlock(&map->freeze_mutex);