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: 9330575 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 C503E60231 for ; Wed, 14 Sep 2016 07:28:26 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B8D3D29A12 for ; Wed, 14 Sep 2016 07:28:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AD1FA29A5D; Wed, 14 Sep 2016 07:28:26 +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=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id C35DE29A12 for ; Wed, 14 Sep 2016 07:28:25 +0000 (UTC) Received: (qmail 13815 invoked by uid 550); 14 Sep 2016 07:25:53 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: kernel-hardening@lists.openwall.com Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 13607 invoked from network); 14 Sep 2016 07:25:46 -0000 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 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 Subject: [kernel-hardening] [RFC v3 17/22] cgroup: Add access check for cgroup_get_from_fd() 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);