From patchwork Wed Sep 14 07:24:10 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 9330573 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 346B060231 for ; Wed, 14 Sep 2016 07:28:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 26F8729A12 for ; Wed, 14 Sep 2016 07:28:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 18F0E29A5D; Wed, 14 Sep 2016 07:28:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 98CB929A12 for ; Wed, 14 Sep 2016 07:28:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761280AbcINH1r (ORCPT ); Wed, 14 Sep 2016 03:27:47 -0400 Received: from smtp-sh.infomaniak.ch ([128.65.195.4]:41893 "EHLO smtp-sh.infomaniak.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759721AbcINH0J (ORCPT ); Wed, 14 Sep 2016 03:26:09 -0400 Received: from smtp6.infomaniak.ch (smtp6.infomaniak.ch [83.166.132.19]) by smtp-sh.infomaniak.ch (8.14.5/8.14.5) with ESMTP id u8E7P7hJ011245 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 14 Sep 2016 09:25:07 +0200 Received: from localhost (ns3096276.ip-94-23-54.eu [94.23.54.103]) (authenticated bits=0) by smtp6.infomaniak.ch (8.14.5/8.14.5) with ESMTP id u8E7P7ws008265; Wed, 14 Sep 2016 09:25:07 +0200 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Alexei Starovoitov , Andy Lutomirski , Arnd Bergmann , Casey Schaufler , Daniel Borkmann , Daniel Mack , David Drysdale , "David S . Miller" , Elena Reshetova , "Eric W . Biederman" , James Morris , Kees Cook , Paul Moore , Sargun Dhillon , "Serge E . Hallyn" , Tejun Heo , Will Drewry , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, netdev@vger.kernel.org, cgroups@vger.kernel.org Subject: [RFC v3 17/22] cgroup: Add access check for cgroup_get_from_fd() Date: Wed, 14 Sep 2016 09:24:10 +0200 Message-Id: <20160914072415.26021-18-mic@digikod.net> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20160914072415.26021-1-mic@digikod.net> References: <20160914072415.26021-1-mic@digikod.net> MIME-Version: 1.0 X-Antivirus: Dr.Web (R) for Unix mail servers drweb plugin ver.6.0.2.8 X-Antivirus-Code: 0x100000 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Add security access check for cgroup backed FD. The "cgroup.procs" file of the corresponding cgroup must be readable to identify the cgroup, and writable to prove that the current process can manage this cgroup (e.g. through delegation). This is similar to the check done by cgroup_procs_write_permission(). Signed-off-by: Mickaël Salaün Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Daniel Borkmann Cc: Daniel Mack Cc: David S. Miller Cc: Kees Cook Cc: Tejun Heo --- include/linux/cgroup.h | 2 +- kernel/bpf/arraymap.c | 2 +- kernel/bpf/syscall.c | 6 +++--- kernel/cgroup.c | 16 +++++++++++++++- 4 files changed, 20 insertions(+), 6 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c4688742ddc4..5767d471e292 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -87,7 +87,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, struct cgroup_subsys *ss); struct cgroup *cgroup_get_from_path(const char *path); -struct cgroup *cgroup_get_from_fd(int fd); +struct cgroup *cgroup_get_from_fd(int fd, int access_mask); int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index edaab4c87292..1d4de8e0ab13 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -552,7 +552,7 @@ static void *cgroup_fd_array_get_ptr(struct bpf_map *map, struct file *map_file /* not used */, int fd) { - return cgroup_get_from_fd(fd); + return cgroup_get_from_fd(fd, MAY_READ); } static void cgroup_fd_array_put_ptr(void *ptr) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index e9c5add327e6..f90225dbbb59 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -17,6 +17,7 @@ #include #include #include +#include DEFINE_PER_CPU(int, bpf_prog_active); @@ -863,7 +864,7 @@ static int bpf_prog_attach(const union bpf_attr *attr) if (IS_ERR(prog)) return PTR_ERR(prog); - cgrp = cgroup_get_from_fd(attr->target_fd); + cgrp = cgroup_get_from_fd(attr->target_fd, MAY_WRITE); if (IS_ERR(cgrp)) { bpf_prog_put(prog); return PTR_ERR(cgrp); @@ -891,10 +892,9 @@ static int bpf_prog_detach(const union bpf_attr *attr) if (!capable(CAP_NET_ADMIN)) return -EPERM; - cgrp = cgroup_get_from_fd(attr->target_fd); + cgrp = cgroup_get_from_fd(attr->target_fd, MAY_WRITE); if (IS_ERR(cgrp)) return PTR_ERR(cgrp); - result = cgroup_bpf_update(cgrp, NULL, attr->attach_type); cgroup_put(cgrp); break; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 48b650a640a9..3bbaf3f02ed2 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -6241,17 +6241,20 @@ EXPORT_SYMBOL_GPL(cgroup_get_from_path); /** * cgroup_get_from_fd - get a cgroup pointer from a fd * @fd: fd obtained by open(cgroup2_dir) + * @access_mask: contains the permission mask * * Find the cgroup from a fd which should be obtained * by opening a cgroup directory. Returns a pointer to the * cgroup on success. ERR_PTR is returned if the cgroup * cannot be found. */ -struct cgroup *cgroup_get_from_fd(int fd) +struct cgroup *cgroup_get_from_fd(int fd, int access_mask) { struct cgroup_subsys_state *css; struct cgroup *cgrp; struct file *f; + struct inode *inode; + int ret; f = fget_raw(fd); if (!f) @@ -6268,6 +6271,17 @@ struct cgroup *cgroup_get_from_fd(int fd) return ERR_PTR(-EBADF); } + ret = -ENOMEM; + inode = kernfs_get_inode(f->f_path.dentry->d_sb, cgrp->procs_file.kn); + if (inode) { + ret = inode_permission(inode, access_mask); + iput(inode); + } + if (ret) { + cgroup_put(cgrp); + return ERR_PTR(ret); + } + return cgrp; } EXPORT_SYMBOL_GPL(cgroup_get_from_fd);