linux-kernel - Re: [PATCH bpf-next v3 1/9] bpf: Implement task local storage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CACYkzJ6t12AORyTzAP_P3bZG-_K_01h7DVaUmYTWCd-8U-8-bQ@mail.gmail.com>
Date:   Wed, 4 Nov 2020 23:54:09 +0100
From:   KP Singh <kpsingh@...omium.org>
To:     Martin KaFai Lau <kafai@...com>
Cc:     open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Paul Turner <pjt@...gle.com>, Jann Horn <jannh@...gle.com>,
        Hao Luo <haoluo@...gle.com>
Subject: Re: [PATCH bpf-next v3 1/9] bpf: Implement task local storage

> > +     WARN_ON_ONCE(!rcu_read_lock_held());
> > +     task = pid_task(pid, PIDTYPE_PID);
> > +     if (!task) {
> > +             err = -ENOENT;
> > +             goto out;
> > +     }
> > +
> > +     sdata = bpf_local_storage_update(
> > +             task, (struct bpf_local_storage_map *)map, value, map_flags);
> It seems the task is protected by rcu here and the task may be going away.
> Is it ok?
>
> or the following comment in the later "BPF_CALL_4(bpf_task_storage_get, ...)"
> is no longer valid?
>         /* This helper must only called from where the task is guaranteed
>          * to have a refcount and cannot be freed.
>          */

I reworded this (and the other similar comment) as:

/* This helper must only be called from places where the lifetime of the task
* is guaranteed. Either by being refcounted or by being protected
* by an RCU read-side critical section.
*/