Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751349AbdH1V5R (ORCPT ); Mon, 28 Aug 2017 17:57:17 -0400 Received: from mail-io0-f174.google.com ([209.85.223.174]:38405 "EHLO mail-io0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750841AbdH1V5P (ORCPT ); Mon, 28 Aug 2017 17:57:15 -0400 X-Google-Smtp-Source: ADKCNb4VhvpEj4lj7iRGfyQ5gvMutY1S08u1SURcx66fY8lowX3HrcZ5qY/znHUt4EDnjNGd3JHKnuX52UUxTlE2N+I= MIME-Version: 1.0 In-Reply-To: <20170828214957.GJ4757@magnolia> References: <1503956111-36652-1-git-send-email-keescook@chromium.org> <1503956111-36652-16-git-send-email-keescook@chromium.org> <20170828214957.GJ4757@magnolia> From: Kees Cook Date: Mon, 28 Aug 2017 14:57:14 -0700 X-Google-Sender-Auth: 9jGwgRQhf97ZywEaVGU4YoPHejM Message-ID: Subject: Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache To: "Darrick J. Wong" Cc: LKML , David Windsor , linux-xfs@vger.kernel.org, Linux-MM , "kernel-hardening@lists.openwall.com" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1567 Lines: 43 On Mon, Aug 28, 2017 at 2:49 PM, Darrick J. Wong wrote: > On Mon, Aug 28, 2017 at 02:34:56PM -0700, Kees Cook wrote: >> 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; > > Hmm, what happens when mem_size > sizeof(if_inline_data)? A slab object > will be allocated for ifp->if_u1.if_data which can then be used for > readlink in the same manner as the example usage trace below. Does > that allocated object have a need for a usercopy annotation like > the one we're adding for if_inline_data? Or is that already covered > elsewhere? Yeah, the xfs helper kmem_alloc() is used in the other case, which ultimately boils down to a call to kmalloc(), which is entirely whitelisted by an earlier patch in the series: https://lkml.org/lkml/2017/8/28/1026 (It's possible that at some future time we can start segregating kernel-only kmallocs from usercopy-able kmallocs, but for now, there are no plans for this.) -Kees -- Kees Cook Pixel Security