From: "Mickaël Salaün" <mic@digikod.net>
To: Jann Horn <jann@thejh.net>
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 07/22] landlock: Handle file comparisons
Date: Thu, 15 Sep 2016 00:39:33 +0200 [thread overview]
Message-ID: <57D9D1A5.90801@digikod.net> (raw)
In-Reply-To: <20160914190723.GB5617@pc.thejh.net>
[-- Attachment #1.1: Type: text/plain, Size: 3266 bytes --]
On 14/09/2016 21:07, Jann Horn wrote:
> On Wed, Sep 14, 2016 at 09:24:00AM +0200, Mickaël Salaün wrote:
>> Add eBPF functions to compare file system access with a Landlock file
>> system handle:
>> * bpf_landlock_cmp_fs_prop_with_struct_file(prop, map, map_op, file)
>> This function allows to compare the dentry, inode, device or mount
>> point of the currently accessed file, with a reference handle.
>> * bpf_landlock_cmp_fs_beneath_with_struct_file(opt, map, map_op, file)
>> This function allows an eBPF program to check if the current accessed
>> file is the same or in the hierarchy of a reference handle.
> [...]
>> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
>> index 94256597eacd..edaab4c87292 100644
>> --- a/kernel/bpf/arraymap.c
>> +++ b/kernel/bpf/arraymap.c
>> @@ -603,6 +605,9 @@ static void landlock_put_handle(struct map_landlock_handle *handle)
>> enum bpf_map_handle_type handle_type = handle->type;
>>
>> switch (handle_type) {
>> + case BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD:
>> + path_put(&handle->path);
>> + break;
>> case BPF_MAP_HANDLE_TYPE_UNSPEC:
>> default:
>> WARN_ON(1);
> [...]
>> diff --git a/security/landlock/checker_fs.c b/security/landlock/checker_fs.c
>> new file mode 100644
>> index 000000000000..39eb85dc7d18
>> --- /dev/null
>> +++ b/security/landlock/checker_fs.c
> [...]
>> +static inline u64 bpf_landlock_cmp_fs_prop_with_struct_file(u64 r1_property,
>> + u64 r2_map, u64 r3_map_op, u64 r4_file, u64 r5)
>> +{
>> + u8 property = (u8) r1_property;
>> + struct bpf_map *map = (struct bpf_map *) (unsigned long) r2_map;
>> + enum bpf_map_array_op map_op = r3_map_op;
>> + struct file *file = (struct file *) (unsigned long) r4_file;
>> + struct bpf_array *array = container_of(map, struct bpf_array, map);
>> + struct path *p1, *p2;
>> + struct map_landlock_handle *handle;
>> + int i;
>
> Please don't use int when iterating over an array, use size_t.
OK, I will use size_t.
>
>
>> + /* for now, only handle OP_OR */
>
> Is "OP_OR" an appropriate name for something that ANDs the success of
> checks?
>
>
> [...]
>> + synchronize_rcu();
>
> Can you put a comment here that explains what's going on?
Hum, this should not be here.
>
>
>> + for (i = 0; i < array->n_entries; i++) {
>> + bool result_dentry = !(property & LANDLOCK_FLAG_FS_DENTRY);
>> + bool result_inode = !(property & LANDLOCK_FLAG_FS_INODE);
>> + bool result_device = !(property & LANDLOCK_FLAG_FS_DEVICE);
>> + bool result_mount = !(property & LANDLOCK_FLAG_FS_MOUNT);
>> +
>> + handle = (struct map_landlock_handle *)
>> + (array->value + array->elem_size * i);
>> +
>> + if (handle->type != BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD) {
>> + WARN_ON(1);
>> + return -EFAULT;
>> + }
>> + p1 = &handle->path;
>> +
>> + if (!result_dentry && p1->dentry == p2->dentry)
>> + result_dentry = true;
>
> Why is this safe? As far as I can tell, this is not in an RCU read-side
> critical section (synchronize_rcu() was just called), and no lock has been
> taken. What prevents someone from removing the arraymap entry while we're
> looking at it? Am I missing something?
I will try to properly deal with RCU.
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 455 bytes --]
next prev parent reply other threads:[~2016-09-14 22:39 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
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 [this message]
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
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=57D9D1A5.90801@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=jann@thejh.net \
--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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).