Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751990AbdH2KMv (ORCPT ); Tue, 29 Aug 2017 06:12:51 -0400 Received: from out2-smtp.messagingengine.com ([66.111.4.26]:54653 "EHLO out2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751710AbdH2KMt (ORCPT ); Tue, 29 Aug 2017 06:12:49 -0400 X-ME-Sender: X-Sasl-enc: HQbaFtnMu6fB8l19Y7XQgt2Cg9wFIdv6kwDXzwH/+tR7 1504001568 Subject: Re: [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache slab cache To: Kees Cook , linux-kernel@vger.kernel.org Cc: David Windsor , Salah Triki , linux-mm@kvack.org, kernel-hardening@lists.openwall.com References: <1503956111-36652-1-git-send-email-keescook@chromium.org> <1503956111-36652-11-git-send-email-keescook@chromium.org> From: Luis de Bethencourt Message-ID: <4bcfaf44-a951-f730-638c-65e44bb2cec4@kernel.org> Date: Tue, 29 Aug 2017 11:12:47 +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: <1503956111-36652-11-git-send-email-keescook@chromium.org> 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: 3209 Lines: 95 Hello Kees, This is great. Thanks :) Will merge into my befs tree. 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; > >