From: "Mickaël Salaün" <mic@digikod.net>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: linux-kernel@vger.kernel.org, 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] Re: [RFC v3 03/22] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles
Date: Thu, 15 Sep 2016 01:22:49 +0200 [thread overview]
Message-ID: <57D9DBC9.2010605@digikod.net> (raw)
In-Reply-To: <20160914185157.GA53542@ast-mbp.thefacebook.com>
[-- Attachment #1.1: Type: text/plain, Size: 5140 bytes --]
On 14/09/2016 20:51, Alexei Starovoitov wrote:
> On Wed, Sep 14, 2016 at 09:23:56AM +0200, Mickaël Salaün wrote:
>> This new arraymap looks like a set and brings new properties:
>> * strong typing of entries: the eBPF functions get the array type of
>> elements instead of CONST_PTR_TO_MAP (e.g.
>> CONST_PTR_TO_LANDLOCK_HANDLE_FS);
>> * force sequential filling (i.e. replace or append-only update), which
>> allow quick browsing of all entries.
>>
>> This strong typing is useful to statically check if the content of a map
>> can be passed to an eBPF function. For example, Landlock use it to store
>> and manage kernel objects (e.g. struct file) instead of dealing with
>> userland raw data. This improve efficiency and ensure that an eBPF
>> program can only call functions with the right high-level arguments.
>>
>> The enum bpf_map_handle_type list low-level types (e.g.
>> BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD) which are identified when
>> updating a map entry (handle). This handle types are used to infer a
>> high-level arraymap type which are listed in enum bpf_map_array_type
>> (e.g. BPF_MAP_ARRAY_TYPE_LANDLOCK_FS).
>>
>> For now, this new arraymap is only used by Landlock LSM (cf. next
>> commits) but it could be useful for other needs.
>>
>> Changes since v2:
>> * add a RLIMIT_NOFILE-based limit to the maximum number of arraymap
>> handle entries (suggested by Andy Lutomirski)
>> * remove useless checks
>>
>> Changes since v1:
>> * arraymap of handles replace custom checker groups
>> * simpler userland API
>>
>> 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: David S. Miller <davem@davemloft.net>
>> Cc: Kees Cook <keescook@chromium.org>
>> Link: https://lkml.kernel.org/r/CALCETrWwTiz3kZTkEgOW24-DvhQq6LftwEXh77FD2G5o71yD7g@mail.gmail.com
>> ---
>> include/linux/bpf.h | 14 ++++
>> include/uapi/linux/bpf.h | 18 +++++
>> kernel/bpf/arraymap.c | 203 +++++++++++++++++++++++++++++++++++++++++++++++
>> kernel/bpf/verifier.c | 12 ++-
>> 4 files changed, 246 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index fa9a988400d9..eae4ce4542c1 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -13,6 +13,10 @@
>> #include <linux/percpu.h>
>> #include <linux/err.h>
>>
>> +#ifdef CONFIG_SECURITY_LANDLOCK
>> +#include <linux/fs.h> /* struct file */
>> +#endif /* CONFIG_SECURITY_LANDLOCK */
>> +
>> struct perf_event;
>> struct bpf_map;
>>
>> @@ -38,6 +42,7 @@ struct bpf_map_ops {
>> struct bpf_map {
>> atomic_t refcnt;
>> enum bpf_map_type map_type;
>> + enum bpf_map_array_type map_array_type;
>> u32 key_size;
>> u32 value_size;
>> u32 max_entries;
>> @@ -187,6 +192,9 @@ struct bpf_array {
>> */
>> enum bpf_prog_type owner_prog_type;
>> bool owner_jited;
>> +#ifdef CONFIG_SECURITY_LANDLOCK
>> + u32 n_entries; /* number of entries in a handle array */
>> +#endif /* CONFIG_SECURITY_LANDLOCK */
>> union {
>> char value[0] __aligned(8);
>> void *ptrs[0] __aligned(8);
>> @@ -194,6 +202,12 @@ struct bpf_array {
>> };
>> };
>>
>> +#ifdef CONFIG_SECURITY_LANDLOCK
>> +struct map_landlock_handle {
>> + u32 type; /* enum bpf_map_handle_type */
>> +};
>> +#endif /* CONFIG_SECURITY_LANDLOCK */
>> +
>> #define MAX_TAIL_CALL_CNT 32
>>
>> struct bpf_event_entry {
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 7cd36166f9b7..b68de57f7ab8 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -87,6 +87,15 @@ enum bpf_map_type {
>> BPF_MAP_TYPE_PERCPU_ARRAY,
>> BPF_MAP_TYPE_STACK_TRACE,P_TYPE_CGROUP_ARRAY
>> BPF_MAP_TYPE_CGROUP_ARRAY,
>> + BPF_MAP_TYPE_LANDLOCK_ARRAY,
>> +};
>> +
>> +enum bpf_map_array_type {
>> + BPF_MAP_ARRAY_TYPE_UNSPEC,
>> +};
>> +
>> +enum bpf_map_handle_type {
>> + BPF_MAP_HANDLE_TYPE_UNSPEC,
>> };
>
> missing something. why it has to be special to have it's own
> fd array implementation?
> Please take a look how BPF_MAP_TYPE_PERF_EVENT_ARRAY,
> BPF_MAP_TYPE_CGROUP_ARRAY and BPF_MAP_TYPE_PROG_ARRAY are done.
> The all store objects into array map that user space passes via FD.
> I think the same model should apply here.
The idea is to have multiple way for userland to describe a resource
(e.g. an open file descriptor, a path or a glob pattern). The kernel
representation could then be a "struct path *" or dedicated types (e.g.
custom glob).
Another interesting point (that could replace
check_map_func_compatibility()) is that BPF_MAP_TYPE_LANDLOCK_ARRAY
translate to dedicated (abstract) types (instead of CONST_PTR_TO_MAP)
thanks to bpf_reg_type_from_map(). This is useful to abstract userland
(map) interface with kernel object(s) dealing with that type.
A third point is that BPF_MAP_TYPE_LANDLOCK_ARRAY is a kind of set. It
is optimized to quickly walk through all the elements in a sequential way.
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next prev parent reply other threads:[~2016-09-14 23:22 UTC|newest]
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 [this message]
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 ` [kernel-hardening] [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks Mickaël Salaün
2016-09-14 18:27 ` [kernel-hardening] " 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
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