From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A494CC433E0 for ; Tue, 7 Jul 2020 11:41:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 81B0C2073E for ; Tue, 7 Jul 2020 11:41:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728256AbgGGLlJ (ORCPT ); Tue, 7 Jul 2020 07:41:09 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:37729 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726805AbgGGLlI (ORCPT ); Tue, 7 Jul 2020 07:41:08 -0400 Received: from ip5f5af08c.dynamic.kabel-deutschland.de ([95.90.240.140] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jslyC-0003t7-Fn; Tue, 07 Jul 2020 11:41:04 +0000 Date: Tue, 7 Jul 2020 13:41:03 +0200 From: Christian Brauner To: Kees Cook Cc: linux-kernel@vger.kernel.org, Sargun Dhillon , Christian Brauner , Tycho Andersen , David Laight , Christoph Hellwig , "David S. Miller" , Jakub Kicinski , Alexander Viro , Aleksa Sarai , Matt Denton , Jann Horn , Chris Palmer , Robert Sesek , Giuseppe Scrivano , Greg Kroah-Hartman , Andy Lutomirski , Will Drewry , Shuah Khan , netdev@vger.kernel.org, containers@lists.linux-foundation.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v6 1/7] net/scm: Regularize compat handling of scm_detach_fds() Message-ID: <20200707114103.lkfbt3kdtturp42z@wittgenstein> References: <20200706201720.3482959-1-keescook@chromium.org> <20200706201720.3482959-2-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200706201720.3482959-2-keescook@chromium.org> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jul 06, 2020 at 01:17:14PM -0700, Kees Cook wrote: > Duplicate the cleanups from commit 2618d530dd8b ("net/scm: cleanup > scm_detach_fds") into the compat code. > > Move the check added in commit 1f466e1f15cf ("net: cleanly handle kernel > vs user buffers for ->msg_control") to before the compat call, even > though it should be impossible for an in-kernel call to also be compat. > > Correct the int "flags" argument to unsigned int to match fd_install() > and similar APIs. > > Regularize any remaining differences, including a whitespace issue, > a checkpatch warning, and add the check from commit 6900317f5eff ("net, > scm: fix PaX detected msg_controllen overflow in scm_detach_fds") which > fixed an overflow unique to 64-bit. To avoid confusion when comparing > the compat handler to the native handler, just include the same check > in the compat handler. > > Fixes: 48a87cc26c13 ("net: netprio: fd passed in SCM_RIGHTS datagram not set correctly") > Fixes: d84295067fc7 ("net: net_cls: fd passed in SCM_RIGHTS datagram not set correctly") > Signed-off-by: Kees Cook > --- Thanks. Just a comment below. Acked-by: Christian Brauner > include/net/scm.h | 1 + > net/compat.c | 55 +++++++++++++++++++++-------------------------- > net/core/scm.c | 18 ++++++++-------- > 3 files changed, 35 insertions(+), 39 deletions(-) > > diff --git a/include/net/scm.h b/include/net/scm.h > index 1ce365f4c256..581a94d6c613 100644 > --- a/include/net/scm.h > +++ b/include/net/scm.h > @@ -37,6 +37,7 @@ struct scm_cookie { > #endif > }; > > +int __scm_install_fd(struct file *file, int __user *ufd, unsigned int o_flags); > void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm); > void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm); > int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm); > diff --git a/net/compat.c b/net/compat.c > index 5e3041a2c37d..27d477fdcaa0 100644 > --- a/net/compat.c > +++ b/net/compat.c > @@ -281,39 +281,31 @@ int put_cmsg_compat(struct msghdr *kmsg, int level, int type, int len, void *dat > return 0; > } > > -void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm) > +static int scm_max_fds_compat(struct msghdr *msg) > { > - struct compat_cmsghdr __user *cm = (struct compat_cmsghdr __user *) kmsg->msg_control; > - int fdmax = (kmsg->msg_controllen - sizeof(struct compat_cmsghdr)) / sizeof(int); > - int fdnum = scm->fp->count; > - struct file **fp = scm->fp->fp; > - int __user *cmfptr; > - int err = 0, i; > + if (msg->msg_controllen <= sizeof(struct compat_cmsghdr)) > + return 0; > + return (msg->msg_controllen - sizeof(struct compat_cmsghdr)) / sizeof(int); > +} > > - if (fdnum < fdmax) > - fdmax = fdnum; > +void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm) > +{ > + struct compat_cmsghdr __user *cm = > + (struct compat_cmsghdr __user *)msg->msg_control; > + unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; > + int fdmax = min_t(int, scm_max_fds_compat(msg), scm->fp->count); Just a note that SCM_RIGHTS fd-sending is limited to 253 (SCM_MAX_FD) fds so min_t should never ouput > SCM_MAX_FD here afaict. > + int __user *cmsg_data = CMSG_USER_DATA(cm); > + int err = 0, i; > > - for (i = 0, cmfptr = (int __user *) CMSG_COMPAT_DATA(cm); i < fdmax; i++, cmfptr++) { > - int new_fd; > - err = security_file_receive(fp[i]); > + for (i = 0; i < fdmax; i++) { > + err = __scm_install_fd(scm->fp->fp[i], cmsg_data + i, o_flags); > if (err) > break; > - err = get_unused_fd_flags(MSG_CMSG_CLOEXEC & kmsg->msg_flags > - ? O_CLOEXEC : 0); > - if (err < 0) > - break; > - new_fd = err; > - err = put_user(new_fd, cmfptr); > - if (err) { > - put_unused_fd(new_fd); > - break; > - } > - /* Bump the usage count and install the file. */ > - fd_install(new_fd, get_file(fp[i])); > } > > if (i > 0) { > int cmlen = CMSG_COMPAT_LEN(i * sizeof(int)); > + > err = put_user(SOL_SOCKET, &cm->cmsg_level); > if (!err) > err = put_user(SCM_RIGHTS, &cm->cmsg_type); > @@ -321,16 +313,19 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm) > err = put_user(cmlen, &cm->cmsg_len); > if (!err) { > cmlen = CMSG_COMPAT_SPACE(i * sizeof(int)); > - kmsg->msg_control += cmlen; > - kmsg->msg_controllen -= cmlen; > + if (msg->msg_controllen < cmlen) > + cmlen = msg->msg_controllen; > + msg->msg_control += cmlen; > + msg->msg_controllen -= cmlen; > } > } > - if (i < fdnum) > - kmsg->msg_flags |= MSG_CTRUNC; > + > + if (i < scm->fp->count || (scm->fp->count && fdmax <= 0)) I think fdmax can't be < 0 after your changes? scm_max_fds() guarantees that fdmax is always >= 0 and min_t() guarantees that fdmax <= scm->fp->count. So the check should technically be :) if (i < scm->fp->count || scm->fp->count && fdmax == 0) > + msg->msg_flags |= MSG_CTRUNC; > > /* > - * All of the files that fit in the message have had their > - * usage counts incremented, so we just free the list. > + * All of the files that fit in the message have had their usage counts > + * incremented, so we just free the list. > */ > __scm_destroy(scm); > } > diff --git a/net/core/scm.c b/net/core/scm.c > index 875df1c2989d..6151678c73ed 100644 > --- a/net/core/scm.c > +++ b/net/core/scm.c > @@ -280,7 +280,7 @@ void put_cmsg_scm_timestamping(struct msghdr *msg, struct scm_timestamping_inter > } > EXPORT_SYMBOL(put_cmsg_scm_timestamping); > > -static int __scm_install_fd(struct file *file, int __user *ufd, int o_flags) > +int __scm_install_fd(struct file *file, int __user *ufd, unsigned int o_flags) > { > struct socket *sock; > int new_fd; > @@ -319,29 +319,29 @@ static int scm_max_fds(struct msghdr *msg) > > void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm) > { > - struct cmsghdr __user *cm > - = (__force struct cmsghdr __user*)msg->msg_control; > - int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; > + struct cmsghdr __user *cm = > + (__force struct cmsghdr __user *)msg->msg_control; > + unsigned int o_flags = (msg->msg_flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0; > int fdmax = min_t(int, scm_max_fds(msg), scm->fp->count); > int __user *cmsg_data = CMSG_USER_DATA(cm); > int err = 0, i; > > + /* no use for FD passing from kernel space callers */ > + if (WARN_ON_ONCE(!msg->msg_control_is_user)) > + return; > + > if (msg->msg_flags & MSG_CMSG_COMPAT) { > scm_detach_fds_compat(msg, scm); > return; > } > > - /* no use for FD passing from kernel space callers */ > - if (WARN_ON_ONCE(!msg->msg_control_is_user)) > - return; > - > for (i = 0; i < fdmax; i++) { > err = __scm_install_fd(scm->fp->fp[i], cmsg_data + i, o_flags); > if (err) > break; > } > > - if (i > 0) { > + if (i > 0) { > int cmlen = CMSG_LEN(i * sizeof(int)); > > err = put_user(SOL_SOCKET, &cm->cmsg_level); > -- > 2.25.1 >