Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751349AbdH2RKS (ORCPT ); Tue, 29 Aug 2017 13:10:18 -0400 Received: from out2-smtp.messagingengine.com ([66.111.4.26]:51253 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751180AbdH2RKQ (ORCPT ); Tue, 29 Aug 2017 13:10:16 -0400 X-ME-Sender: X-Sasl-enc: H73YR4jwB4r/PcaHT7T3VPXU+TqKiA02J68F8bHq9bBQ 1504026616 Subject: Re: [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache slab cache To: Kees Cook Cc: LKML , David Windsor , Salah Triki , Linux-MM , "kernel-hardening@lists.openwall.com" References: <1503956111-36652-1-git-send-email-keescook@chromium.org> <1503956111-36652-11-git-send-email-keescook@chromium.org> <4bcfaf44-a951-f730-638c-65e44bb2cec4@kernel.org> From: Luis de Bethencourt Message-ID: <6a2eb4e1-1654-5025-4edd-dd3faf978aad@kernel.org> Date: Tue, 29 Aug 2017 18:10:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4176 Lines: 120 On 08/29/2017 04:36 PM, Kees Cook wrote: > On Tue, Aug 29, 2017 at 3:12 AM, Luis de Bethencourt wrote: >> Hello Kees, >> >> This is great. Thanks :) >> >> Will merge into my befs tree. > > Hi! Actually, this depends on the rest of the series, which should be > merged together. If you can Ack this, I'll include it in my usercopy > tree. > > Thanks! > > -Kees > Sure! Acked-by: Luis de Bethencourt >> >> Luis >> >> >> On 08/28/2017 10:34 PM, Kees Cook wrote: >>> >>> From: David Windsor >>> >>> befs symlink pathnames, stored in struct befs_inode_info.i_data.symlink >>> and therefore contained in the befs_inode_cache slab cache, need to be >>> copied to/from userspace. >>> >>> cache object allocation: >>> fs/befs/linuxvfs.c: >>> befs_alloc_inode(...): >>> ... >>> bi = kmem_cache_alloc(befs_inode_cachep, GFP_KERNEL); >>> ... >>> return &bi->vfs_inode; >>> >>> befs_iget(...): >>> ... >>> strlcpy(befs_ino->i_data.symlink, raw_inode->data.symlink, >>> BEFS_SYMLINK_LEN); >>> ... >>> inode->i_link = befs_ino->i_data.symlink; >>> >>> example usage trace: >>> readlink_copy+0x43/0x70 >>> vfs_readlink+0x62/0x110 >>> SyS_readlinkat+0x100/0x130 >>> >>> fs/namei.c: >>> readlink_copy(..., link): >>> ... >>> copy_to_user(..., link, len); >>> >>> (inlined in vfs_readlink) >>> generic_readlink(dentry, ...): >>> struct inode *inode = d_inode(dentry); >>> const char *link = inode->i_link; >>> ... >>> readlink_copy(..., link); >>> >>> In support of usercopy hardening, this patch defines a region in the >>> befs_inode_cache slab cache in which userspace copy operations are >>> allowed. >>> >>> This region is known as the slab cache's usercopy region. Slab caches can >>> now check that each copy operation involving cache-managed memory falls >>> entirely within the slab's usercopy region. >>> >>> This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY >>> whitelisting code in the last public patch of grsecurity/PaX based on my >>> understanding of the code. Changes or omissions from the original code are >>> mine and don't reflect the original grsecurity/PaX code. >>> >>> Signed-off-by: David Windsor >>> [kees: adjust commit log, provide usage trace] >>> Cc: Luis de Bethencourt >>> Cc: Salah Triki >>> Signed-off-by: Kees Cook >>> --- >>> fs/befs/linuxvfs.c | 14 +++++++++----- >>> 1 file changed, 9 insertions(+), 5 deletions(-) >>> >>> diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c >>> index 4a4a5a366158..1c2dcbee79dd 100644 >>> --- a/fs/befs/linuxvfs.c >>> +++ b/fs/befs/linuxvfs.c >>> @@ -444,11 +444,15 @@ static struct inode *befs_iget(struct super_block >>> *sb, unsigned long ino) >>> static int __init >>> befs_init_inodecache(void) >>> { >>> - befs_inode_cachep = kmem_cache_create("befs_inode_cache", >>> - sizeof (struct >>> befs_inode_info), >>> - 0, (SLAB_RECLAIM_ACCOUNT| >>> - >>> SLAB_MEM_SPREAD|SLAB_ACCOUNT), >>> - init_once); >>> + befs_inode_cachep = kmem_cache_create_usercopy("befs_inode_cache", >>> + sizeof(struct befs_inode_info), 0, >>> + (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD| >>> + SLAB_ACCOUNT), >>> + offsetof(struct befs_inode_info, >>> + i_data.symlink), >>> + sizeof_field(struct befs_inode_info, >>> + i_data.symlink), >>> + init_once); >>> if (befs_inode_cachep == NULL) >>> return -ENOMEM; >>> >> >> > > >