Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20181016223322.16844-1-christian@brauner.io> <20181029145818.4bqmy25itjnqhodg@brauner.io>
 <CAGXu5jJwSRQ3dOgNW_X0Fk+8gT+ACiBZPJ79g-aCfqiWsm=ewg@mail.gmail.com>
In-Reply-To: <CAGXu5jJwSRQ3dOgNW_X0Fk+8gT+ACiBZPJ79g-aCfqiWsm=ewg@mail.gmail.com>
From:   Christian Brauner <christian.brauner@canonical.com>
Date:   Sun, 9 Dec 2018 17:40:09 +0100
Message-ID: <CAPP7u0U72jSkT3km-E2imQdOvk-WRaDCH4t--N07mh8my7PvOQ@mail.gmail.com>
Subject: Re: [PATCH v3 0/2] sysctl: handle overflow for file-max
To:     Kees Cook <keescook@chromium.org>
Cc:     Christian Brauner <christian@brauner.io>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>, mcgrof@kernel.org,
        joe.lawrence@redhat.com, Waiman Long <longman@redhat.com>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Linux API <linux-api@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Oct 29, 2018 at 10:44 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Oct 29, 2018 at 7:58 AM, Christian Brauner <christian@brauner.io> wrote:
> > On Wed, Oct 17, 2018 at 12:33:20AM +0200, Christian Brauner wrote:
> >> Hey,
> >>
> >> Here is v3 of this patchset. Changelogs are in the individual commits.
> >>
> >> Currently, when writing
> >>
> >> echo 18446744073709551616 > /proc/sys/fs/file-max
> >>
> >> /proc/sys/fs/file-max will overflow and be set to 0. That quickly
> >> crashes the system.
> >>
> >> The first version of this patch intended to detect the overflow and cap
> >> at ULONG_MAX. However, we should not do this and rather return EINVAL on
> >> overflow. The reasons are:
> >> - this aligns with other sysctl handlers that simply reject overflows
> >>   (cf. [1], [2], and a bunch of others)
> >> - we already do a partial fail on overflow right now
> >>   Namely, when the TMPBUFLEN is exceeded. So we already reject values
> >>   such as 184467440737095516160 (21 chars) but accept values such as
> >>   18446744073709551616 (20 chars) but both are overflows. So we should
> >>   just always reject 64bit overflows and not special-case this based on
> >>   the number of chars.
> >>
> >> (This patchset is in reference to https://lkml.org/lkml/2018/10/11/585.)
> >
> > Just so that we don't forget, can we make sure that this gets picked
> > into linux-next? :)
>
> I was hoping akpm would take this? Andrew, does the v3 look okay to you?

gentle ping again :)

Christian