Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751885AbdH1Vhr (ORCPT ); Mon, 28 Aug 2017 17:37:47 -0400 Received: from mail-pf0-f172.google.com ([209.85.192.172]:34429 "EHLO mail-pf0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751523AbdH1VfY (ORCPT ); Mon, 28 Aug 2017 17:35:24 -0400 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , David Windsor , Luis de Bethencourt , Salah Triki , linux-mm@kvack.org, kernel-hardening@lists.openwall.com Subject: [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache slab cache Date: Mon, 28 Aug 2017 14:34:51 -0700 Message-Id: <1503956111-36652-11-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1503956111-36652-1-git-send-email-keescook@chromium.org> References: <1503956111-36652-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2896 Lines: 87 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; -- 2.7.4