linux-kernel - Re: [RESEND PATCH v3 0/2] sysctl: handle overflow for file-max

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

Message-ID: <CAGXu5jJQgZDec1+WnsU6ttVaMb6j5oqtJ7Zw_YYn4RgWgvc0SA@mail.gmail.com>
Date:   Mon, 7 Jan 2019 15:16:42 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Christian Brauner <christian@...uner.io>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [RESEND PATCH v3 0/2] sysctl: handle overflow for file-max

On Mon, Jan 7, 2019 at 2:27 PM Christian Brauner <christian@...uner.io> wrote:
>
> Hey,
>
> Here is v3 of this patchset. Changelogs are in the individual commits.

Andrew, can you take these? I've already Acked them.

-Kees

>
> 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.)
>
> Thanks!
> Christian
>
> [1]: fb910c42cceb ("sysctl: check for UINT_MAX before unsigned int min/max")
> [2]: 196851bed522 ("s390/topology: correct topology mode proc handler")
>
> Christian Brauner (2):
>   sysctl: handle overflow in proc_get_long
>   sysctl: handle overflow for file-max
>
>  kernel/sysctl.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 46 insertions(+), 1 deletion(-)
>
> --
> 2.19.1
>


-- 
Kees Cook