From: "Mickaël Salaün" <mic@digikod.net> To: linux-kernel@vger.kernel.org Cc: "Mickaël Salaün" <mic@digikod.net>, "Alexei Starovoitov" <ast@kernel.org>, "Andy Lutomirski" <luto@amacapital.net>, "Arnd Bergmann" <arnd@arndb.de>, "Casey Schaufler" <casey@schaufler-ca.com>, "Daniel Borkmann" <daniel@iogearbox.net>, "Daniel Mack" <daniel@zonque.org>, "David Drysdale" <drysdale@google.com>, "David S . Miller" <davem@davemloft.net>, "Elena Reshetova" <elena.reshetova@intel.com>, "Eric W . Biederman" <ebiederm@xmission.com>, "James Morris" <james.l.morris@oracle.com>, "Kees Cook" <keescook@chromium.org>, "Paul Moore" <pmoore@redhat.com>, "Sargun Dhillon" <sargun@sargun.me>, "Serge E . Hallyn" <serge@hallyn.com>, "Tejun Heo" <tj@kernel.org>, "Will Drewry" <wad@chromium.org>, 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: [kernel-hardening] [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks Date: Wed, 14 Sep 2016 09:24:11 +0200 Message-ID: <20160914072415.26021-19-mic@digikod.net> (raw) In-Reply-To: <20160914072415.26021-1-mic@digikod.net> Add a new flag CGRP_NO_NEW_PRIVS for each cgroup. This flag is initially set for all cgroup except the root. The flag is clear when a new process without the no_new_privs flags is attached to the cgroup. If a cgroup is landlocked, then any new attempt, from an unprivileged process, to attach a process without no_new_privs to this cgroup will be denied. This allows to safely manage Landlock rules with cgroup delegation as with seccomp. Signed-off-by: Mickaël Salaün <mic@digikod.net> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Daniel Mack <daniel@zonque.org> Cc: David S. Miller <davem@davemloft.net> Cc: Kees Cook <keescook@chromium.org> Cc: Tejun Heo <tj@kernel.org> --- include/linux/cgroup-defs.h | 7 +++++++ kernel/bpf/syscall.c | 7 ++++--- kernel/cgroup.c | 44 ++++++++++++++++++++++++++++++++++++++++++-- security/landlock/manager.c | 7 +++++++ 4 files changed, 60 insertions(+), 5 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index fe1023bf7b9d..ce0e4c90ae7d 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -59,6 +59,13 @@ enum { * specified at mount time and thus is implemented here. */ CGRP_CPUSET_CLONE_CHILDREN, + /* + * Keep track of the no_new_privs property of processes in the cgroup. + * This is useful to quickly check if all processes in the cgroup have + * their no_new_privs bit on. This flag is initially set to true but + * ANDed with every processes coming in the cgroup. + */ + CGRP_NO_NEW_PRIVS, }; /* cgroup_root->flags */ diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index f90225dbbb59..ff8b53a8a2a0 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -849,9 +849,10 @@ static int bpf_prog_attach(const union bpf_attr *attr) case BPF_CGROUP_LANDLOCK: #ifdef CONFIG_SECURITY_LANDLOCK - if (!capable(CAP_SYS_ADMIN)) - return -EPERM; - + /* + * security/capability check done in landlock_cgroup_set_hook() + * called by cgroup_bpf_update() + */ prog = bpf_prog_get_type(attr->attach_bpf_fd, BPF_PROG_TYPE_LANDLOCK); break; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 3bbaf3f02ed2..913e2d3b6d55 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -62,6 +62,7 @@ #include <linux/proc_ns.h> #include <linux/nsproxy.h> #include <linux/file.h> +#include <linux/bitops.h> #include <net/sock.h> #define CREATE_TRACE_POINTS @@ -1985,6 +1986,7 @@ static void init_cgroup_root(struct cgroup_root *root, strcpy(root->name, opts->name); if (opts->cpuset_clone_children) set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags); + /* no CGRP_NO_NEW_PRIVS flag for the root */ } static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask) @@ -2812,14 +2814,35 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp, LIST_HEAD(preloaded_csets); struct task_struct *task; int ret; +#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_SECURITY_LANDLOCK) + bool no_new_privs; +#endif /* CONFIG_CGROUP_BPF && CONFIG_SECURITY_LANDLOCK */ if (!cgroup_may_migrate_to(dst_cgrp)) return -EBUSY; + task = leader; +#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_SECURITY_LANDLOCK) + no_new_privs = !!(dst_cgrp->flags & BIT_ULL(CGRP_NO_NEW_PRIVS)); + do { + no_new_privs = no_new_privs && task_no_new_privs(task); + if (!no_new_privs) { + if (dst_cgrp->bpf.pinned[BPF_CGROUP_LANDLOCK].hooks && + security_capable_noaudit(current_cred(), + current_user_ns(), + CAP_SYS_ADMIN) != 0) + return -EPERM; + clear_bit(CGRP_NO_NEW_PRIVS, &dst_cgrp->flags); + break; + } + if (!threadgroup) + break; + } while_each_thread(leader, task); +#endif /* CONFIG_CGROUP_BPF && CONFIG_SECURITY_LANDLOCK */ + /* look up all src csets */ spin_lock_irq(&css_set_lock); rcu_read_lock(); - task = leader; do { cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &preloaded_csets); @@ -4345,9 +4368,22 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from) return -EBUSY; mutex_lock(&cgroup_mutex); - percpu_down_write(&cgroup_threadgroup_rwsem); +#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_SECURITY_LANDLOCK) + if (!(from->flags & BIT_ULL(CGRP_NO_NEW_PRIVS))) { + if (to->bpf.pinned[BPF_CGROUP_LANDLOCK].hooks && + security_capable_noaudit(current_cred(), + current_user_ns(), CAP_SYS_ADMIN) != 0) { + pr_warn("%s: EPERM\n", __func__); + ret = -EPERM; + goto out_unlock; + } + pr_warn("%s: no EPERM\n", __func__); + clear_bit(CGRP_NO_NEW_PRIVS, &to->flags); + } +#endif /* CONFIG_CGROUP_BPF && CONFIG_SECURITY_LANDLOCK */ + /* all tasks in @from are being moved, all csets are source */ spin_lock_irq(&css_set_lock); list_for_each_entry(link, &from->cset_links, cset_link) @@ -4378,6 +4414,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from) } while (task && !ret); out_err: cgroup_migrate_finish(&preloaded_csets); +out_unlock: percpu_up_write(&cgroup_threadgroup_rwsem); mutex_unlock(&cgroup_mutex); return ret; @@ -5241,6 +5278,9 @@ static struct cgroup *cgroup_create(struct cgroup *parent) if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags)) set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags); +#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_SECURITY_LANDLOCK) + set_bit(CGRP_NO_NEW_PRIVS, &cgrp->flags); +#endif /* CONFIG_CGROUP_BPF && CONFIG_SECURITY_LANDLOCK */ cgrp->self.serial_nr = css_serial_nr_next++; diff --git a/security/landlock/manager.c b/security/landlock/manager.c index 50aa1305d0d1..479f6990aeff 100644 --- a/security/landlock/manager.c +++ b/security/landlock/manager.c @@ -11,6 +11,7 @@ #include <asm/atomic.h> /* atomic_*() */ #include <asm/page.h> /* PAGE_SIZE */ #include <asm/uaccess.h> /* copy_from_user() */ +#include <linux/bitops.h> /* BIT_ULL() */ #include <linux/bpf.h> /* bpf_prog_put() */ #include <linux/filter.h> /* struct bpf_prog */ #include <linux/kernel.h> /* round_up() */ @@ -267,6 +268,12 @@ struct landlock_hooks *landlock_cgroup_set_hook(struct cgroup *cgrp, if (!prog) return ERR_PTR(-EINVAL); + /* check no_new_privs for tasks in the cgroup */ + if (!(cgrp->flags & BIT_ULL(CGRP_NO_NEW_PRIVS)) && + security_capable_noaudit(current_cred(), + current_user_ns(), CAP_SYS_ADMIN) != 0) + return ERR_PTR(-EPERM); + /* copy the inherited hooks and append a new one */ return landlock_set_hook(cgrp->bpf.effective[BPF_CGROUP_LANDLOCK].hooks, prog, NULL); -- 2.9.3
next prev parent reply index Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-14 7:23 [kernel-hardening] [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing Mickaël Salaün 2016-09-14 7:23 ` [kernel-hardening] [RFC v3 01/22] landlock: Add Kconfig Mickaël Salaün 2016-09-14 7:23 ` [kernel-hardening] [RFC v3 02/22] bpf: Move u64_to_ptr() to BPF headers and inline it Mickaël Salaün 2016-09-14 7:23 ` [kernel-hardening] [RFC v3 03/22] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles Mickaël Salaün 2016-09-14 18:51 ` [kernel-hardening] " Alexei Starovoitov 2016-09-14 23:22 ` Mickaël Salaün 2016-09-14 23:28 ` Alexei Starovoitov 2016-09-15 21:51 ` Mickaël Salaün 2016-10-03 23:53 ` Kees Cook 2016-10-05 22:02 ` Mickaël Salaün 2016-09-14 7:23 ` [kernel-hardening] [RFC v3 04/22] bpf: Set register type according to is_valid_access() Mickaël Salaün 2016-10-19 14:54 ` [kernel-hardening] " Thomas Graf 2016-10-19 15:10 ` Daniel Borkmann 2016-09-14 7:23 ` [kernel-hardening] [RFC v3 05/22] bpf,landlock: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün 2016-10-19 15:01 ` [kernel-hardening] " Thomas Graf 2016-09-14 7:23 ` [kernel-hardening] [RFC v3 06/22] landlock: Add LSM hooks Mickaël Salaün 2016-10-19 15:19 ` [kernel-hardening] " Thomas Graf 2016-10-19 22:42 ` Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 07/22] landlock: Handle file comparisons Mickaël Salaün 2016-09-14 19:07 ` [kernel-hardening] " Jann Horn 2016-09-14 22:39 ` Mickaël Salaün 2016-09-14 21:06 ` Alexei Starovoitov 2016-09-14 23:02 ` Mickaël Salaün 2016-09-14 23:24 ` Alexei Starovoitov 2016-09-15 21:25 ` Mickaël Salaün 2016-09-20 0:12 ` [kernel-hardening] lsm naming dilemma. " Alexei Starovoitov 2016-09-20 1:10 ` [kernel-hardening] " Sargun Dhillon 2016-09-20 16:58 ` Mickaël Salaün 2016-10-03 23:30 ` [kernel-hardening] " Kees Cook 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 08/22] seccomp: Fix documentation for struct seccomp_filter Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 09/22] seccomp: Move struct seccomp_filter in seccomp.h Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 10/22] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 11/22] seccomp,landlock: Handle Landlock hooks per process hierarchy Mickaël Salaün 2016-09-14 18:43 ` [kernel-hardening] " Andy Lutomirski 2016-09-14 22:34 ` Mickaël Salaün 2016-10-03 23:52 ` Kees Cook 2016-10-05 21:05 ` Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 12/22] bpf: Cosmetic change for bpf_prog_attach() Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 13/22] bpf/cgroup: Replace struct bpf_prog with union bpf_object Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 14/22] bpf/cgroup: Make cgroup_bpf_update() return an error code Mickaël Salaün 2016-09-14 21:16 ` [kernel-hardening] " Alexei Starovoitov 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 15/22] bpf/cgroup: Move capability check Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 16/22] bpf/cgroup,landlock: Handle Landlock hooks per cgroup Mickaël Salaün 2016-10-03 23:43 ` [kernel-hardening] " Kees Cook 2016-10-05 20:58 ` Mickaël Salaün 2016-10-05 21:25 ` Kees Cook 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 17/22] cgroup: Add access check for cgroup_get_from_fd() Mickaël Salaün 2016-09-14 22:06 ` [kernel-hardening] " Mickaël Salaün 2016-09-14 7:24 ` Mickaël Salaün [this message] 2016-09-14 18:27 ` [kernel-hardening] Re: [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks Andy Lutomirski 2016-09-14 22:11 ` Mickaël Salaün 2016-09-15 1:25 ` Andy Lutomirski 2016-09-15 2:19 ` Alexei Starovoitov 2016-09-15 2:27 ` Andy Lutomirski 2016-09-15 4:00 ` Alexei Starovoitov 2016-09-15 4:08 ` Andy Lutomirski 2016-09-15 4:31 ` Alexei Starovoitov 2016-09-15 4:38 ` Andy Lutomirski 2016-09-15 4:48 ` Alexei Starovoitov 2016-09-15 19:41 ` Mickaël Salaün 2016-09-20 4:37 ` Sargun Dhillon 2016-09-20 17:02 ` Mickaël Salaün 2016-09-15 19:35 ` Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 19/22] landlock: Add interrupted origin Mickaël Salaün 2016-09-14 18:29 ` [kernel-hardening] " Andy Lutomirski 2016-09-14 22:14 ` Mickaël Salaün 2016-09-15 1:19 ` Andy Lutomirski 2016-10-03 23:46 ` Kees Cook 2016-10-05 21:01 ` Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 20/22] landlock: Add update and debug access flags Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 21/22] bpf,landlock: Add optional skb pointer in the Landlock context Mickaël Salaün 2016-09-14 21:20 ` [kernel-hardening] " Alexei Starovoitov 2016-09-14 22:46 ` Mickaël Salaün 2016-09-14 7:24 ` [kernel-hardening] [RFC v3 22/22] samples/landlock: Add sandbox example Mickaël Salaün 2016-09-14 21:24 ` [kernel-hardening] " Alexei Starovoitov 2016-09-14 14:36 ` [kernel-hardening] RE: [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing David Laight
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20160914072415.26021-19-mic@digikod.net \ --to=mic@digikod.net \ --cc=arnd@arndb.de \ --cc=ast@kernel.org \ --cc=casey@schaufler-ca.com \ --cc=cgroups@vger.kernel.org \ --cc=daniel@iogearbox.net \ --cc=daniel@zonque.org \ --cc=davem@davemloft.net \ --cc=drysdale@google.com \ --cc=ebiederm@xmission.com \ --cc=elena.reshetova@intel.com \ --cc=james.l.morris@oracle.com \ --cc=keescook@chromium.org \ --cc=kernel-hardening@lists.openwall.com \ --cc=linux-api@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-security-module@vger.kernel.org \ --cc=luto@amacapital.net \ --cc=netdev@vger.kernel.org \ --cc=pmoore@redhat.com \ --cc=sargun@sargun.me \ --cc=serge@hallyn.com \ --cc=tj@kernel.org \ --cc=wad@chromium.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
Kernel-hardening Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/kernel-hardening/0 kernel-hardening/git/0.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 kernel-hardening kernel-hardening/ https://lore.kernel.org/kernel-hardening \ kernel-hardening@lists.openwall.com public-inbox-index kernel-hardening Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/com.openwall.lists.kernel-hardening AGPL code for this site: git clone https://public-inbox.org/public-inbox.git