Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752070AbdITUq6 (ORCPT ); Wed, 20 Sep 2017 16:46:58 -0400 Received: from mail-pf0-f176.google.com ([209.85.192.176]:44818 "EHLO mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751928AbdITUqN (ORCPT ); Wed, 20 Sep 2017 16:46:13 -0400 X-Google-Smtp-Source: AOwi7QBudTs6+9IokAgC0t94vW1UuTut8UTpOKHtxDrxTNGgs9P862/RfSJ9M5Sf09tj7XhRwV69ug== From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , David Windsor , Christoph Hellwig , linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com Subject: [PATCH v3 14/31] vxfs: Define usercopy region in vxfs_inode slab cache Date: Wed, 20 Sep 2017 13:45:20 -0700 Message-Id: <1505940337-79069-15-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1505940337-79069-1-git-send-email-keescook@chromium.org> References: <1505940337-79069-1-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: 2585 Lines: 78 From: David Windsor vxfs symlink pathnames, stored in struct vxfs_inode_info field vii_immed.vi_immed and therefore contained in the vxfs_inode slab cache, need to be copied to/from userspace. cache object allocation: fs/freevxfs/vxfs_super.c: vxfs_alloc_inode(...): ... vi = kmem_cache_alloc(vxfs_inode_cachep, GFP_KERNEL); ... return &vi->vfs_inode; fs/freevxfs/vxfs_inode.c: cxfs_iget(...): ... inode->i_link = vip->vii_immed.vi_immed; 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 vxfs_inode 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: Christoph Hellwig Signed-off-by: Kees Cook --- fs/freevxfs/vxfs_super.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/freevxfs/vxfs_super.c b/fs/freevxfs/vxfs_super.c index 455ce5b77e9b..c143e18d5a65 100644 --- a/fs/freevxfs/vxfs_super.c +++ b/fs/freevxfs/vxfs_super.c @@ -332,9 +332,13 @@ vxfs_init(void) { int rv; - vxfs_inode_cachep = kmem_cache_create("vxfs_inode", + vxfs_inode_cachep = kmem_cache_create_usercopy("vxfs_inode", sizeof(struct vxfs_inode_info), 0, - SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL); + SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, + offsetof(struct vxfs_inode_info, vii_immed.vi_immed), + sizeof_field(struct vxfs_inode_info, + vii_immed.vi_immed), + NULL); if (!vxfs_inode_cachep) return -ENOMEM; rv = register_filesystem(&vxfs_fs_type); -- 2.7.4