Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751814AbdH1Vgf (ORCPT ); Mon, 28 Aug 2017 17:36:35 -0400 Received: from mail-pg0-f53.google.com ([74.125.83.53]:35407 "EHLO mail-pg0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751586AbdH1Vf2 (ORCPT ); Mon, 28 Aug 2017 17:35:28 -0400 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , David Windsor , "Darrick J. Wong" , linux-xfs@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com Subject: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache Date: Mon, 28 Aug 2017 14:34:56 -0700 Message-Id: <1503956111-36652-16-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: 3733 Lines: 113 From: David Windsor The XFS inline inode data, stored in struct xfs_inode_t field i_df.if_u2.if_inline_data and therefore contained in the xfs_inode slab cache, needs to be copied to/from userspace. cache object allocation: fs/xfs/xfs_icache.c: xfs_inode_alloc(...): ... ip = kmem_zone_alloc(xfs_inode_zone, KM_SLEEP); fs/xfs/libxfs/xfs_inode_fork.c: xfs_init_local_fork(...): ... if (mem_size <= sizeof(ifp->if_u2.if_inline_data)) ifp->if_u1.if_data = ifp->if_u2.if_inline_data; ... fs/xfs/xfs_symlink.c: xfs_symlink(...): ... xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen); example usage trace: readlink_copy+0x43/0x70 vfs_readlink+0x62/0x110 SyS_readlinkat+0x100/0x130 fs/xfs/xfs_iops.c: (via inode->i_op->get_link) xfs_vn_get_link_inline(...): ... return XFS_I(inode)->i_df.if_u1.if_data; fs/namei.c: readlink_copy(..., link): ... copy_to_user(..., link, len); generic_readlink(dentry, ...): struct inode *inode = d_inode(dentry); const char *link = inode->i_link; ... if (!link) { link = inode->i_op->get_link(dentry, inode, &done); ... readlink_copy(..., link); In support of usercopy hardening, this patch defines a region in the xfs_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: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org Signed-off-by: Kees Cook --- fs/xfs/kmem.h | 10 ++++++++++ fs/xfs/xfs_super.c | 7 +++++-- 2 files changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/xfs/kmem.h b/fs/xfs/kmem.h index 4d85992d75b2..08358f38dee6 100644 --- a/fs/xfs/kmem.h +++ b/fs/xfs/kmem.h @@ -110,6 +110,16 @@ kmem_zone_init_flags(int size, char *zone_name, unsigned long flags, return kmem_cache_create(zone_name, size, 0, flags, construct); } +static inline kmem_zone_t * +kmem_zone_init_flags_usercopy(int size, char *zone_name, unsigned long flags, + size_t useroffset, size_t usersize, + void (*construct)(void *)) +{ + return kmem_cache_create_usercopy(zone_name, size, 0, flags, + useroffset, usersize, construct); +} + + static inline void kmem_zone_free(kmem_zone_t *zone, void *ptr) { diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index 38aaacdbb8b3..6ca428c6f943 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -1829,9 +1829,12 @@ xfs_init_zones(void) goto out_destroy_efd_zone; xfs_inode_zone = - kmem_zone_init_flags(sizeof(xfs_inode_t), "xfs_inode", + kmem_zone_init_flags_usercopy(sizeof(xfs_inode_t), "xfs_inode", KM_ZONE_HWALIGN | KM_ZONE_RECLAIM | KM_ZONE_SPREAD | - KM_ZONE_ACCOUNT, xfs_fs_inode_init_once); + KM_ZONE_ACCOUNT, + offsetof(xfs_inode_t, i_df.if_u2.if_inline_data), + sizeof_field(xfs_inode_t, i_df.if_u2.if_inline_data), + xfs_fs_inode_init_once); if (!xfs_inode_zone) goto out_destroy_efi_zone; -- 2.7.4