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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Mickaël Salaün" <mickael.salaun@ssi.gouv.fr>
Cc: "Mickaël Salaün" <mic@digikod.net>,
	LKML <linux-kernel@vger.kernel.org>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Andy Lutomirski" <luto@amacapital.net>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	"Casey Schaufler" <casey@schaufler-ca.com>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"David Drysdale" <drysdale@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"James Morris" <jmorris@namei.org>, "Jann Horn" <jann@thejh.net>,
	"John Johansen" <john.johansen@canonical.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Kees Cook" <keescook@chromium.org>,
	"Michael Kerrisk" <mtk.manpages@gmail.com>,
	"Paul Moore" <paul@paul-moore.com>,
	"Sargun Dhillon" <sargun@sargun.me>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Stephen Smalley" <sds@tycho.nsa.gov>,
	"Tejun Heo" <tj@kernel.org>,
	"Tetsuo Handa" <penguin-kernel@i-love.sakura.ne.jp>,
	"Thomas Graf" <tgraf@suug.ch>, "Tycho Andersen" <tycho@tycho.ws>,
	"Will Drewry" <wad@chromium.org>,
	"Kernel Hardening" <kernel-hardening@lists.openwall.com>,
	"Linux API" <linux-api@vger.kernel.org>,
	Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
	"LSM List" <linux-security-module@vger.kernel.org>,
	"Network Development" <netdev@vger.kernel.org>
Subject: Re: [PATCH bpf-next v10 06/10] bpf,landlock: Add a new map type: inode
Date: Wed, 31 Jul 2019 11:58:18 -0700
Message-ID: <CAADnVQLqkfVijWoOM29PxCL_yK6K0fr8B89r4c5EKgddevJhGQ@mail.gmail.com> (raw)
In-Reply-To: <a870c2c9-d2f7-e0fa-c8cc-35dbf8b5b87d@ssi.gouv.fr>

On Wed, Jul 31, 2019 at 11:46 AM Mickaël Salaün
<mickael.salaun@ssi.gouv.fr> wrote:
> >> +    for (i = 0; i < htab->n_buckets; i++) {
> >> +            head = select_bucket(htab, i);
> >> +            hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
> >> +                    landlock_inode_remove_map(*((struct inode **)l->key), map);
> >> +            }
> >> +    }
> >> +    htab_map_free(map);
> >> +}
> >
> > user space can delete the map.
> > that will trigger inode_htab_map_free() which will call
> > landlock_inode_remove_map().
> > which will simply itereate the list and delete from the list.
>
> landlock_inode_remove_map() removes the reference to the map (being
> freed) from the inode (with an RCU lock).

I'm going to ignore everything else for now and focus only on this bit,
since it's fundamental issue to address before this discussion can
go any further.
rcu_lock is not a spin_lock. I'm pretty sure you know this.
But you're arguing that it's somehow protecting from the race
I mentioned above?

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-21 21:31 [PATCH bpf-next v10 00/10] Landlock LSM: Toward unprivileged sandboxing Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 01/10] fs,security: Add a new file access type: MAY_CHROOT Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 02/10] bpf: Add expected_attach_triggers and a is_valid_triggers() verifier Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 03/10] bpf,landlock: Define an eBPF program type for Landlock hooks Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 04/10] seccomp,landlock: Enforce Landlock programs per process hierarchy Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 05/10] landlock: Handle filesystem access control Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 06/10] bpf,landlock: Add a new map type: inode Mickaël Salaün
2019-07-27  1:40   ` Alexei Starovoitov
2019-07-31 18:46     ` Mickaël Salaün
2019-07-31 18:58       ` Alexei Starovoitov [this message]
2019-07-31 19:11         ` Mickaël Salaün
2019-08-01 17:35           ` Alexei Starovoitov
2019-08-06 16:24             ` Mickaël Salaün
2019-09-08 22:09       ` Mickaël Salaün
2019-09-08 22:19         ` Al Viro
2019-07-21 21:31 ` [PATCH bpf-next v10 07/10] landlock: Add ptrace restrictions Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 08/10] bpf: Add a Landlock sandbox example Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 09/10] bpf,landlock: Add tests for Landlock Mickaël Salaün
2019-07-21 21:31 ` [PATCH bpf-next v10 10/10] landlock: Add user and kernel documentation " Mickaël Salaün
2019-07-31  1:53   ` Randy Dunlap
2019-08-01 17:03     ` Mickaël Salaün
2019-08-01 17:49       ` Randy Dunlap

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