From: Kees Cook <keescook@chromium.org>
To: Matteo Croce <mcroce@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v5] proc/sysctl: add shared variables for range check
Date: Tue, 30 Apr 2019 11:14:20 -0700 [thread overview]
Message-ID: <CAGXu5jJG1D6YvTaSY3hpB8_APmwe=rGn8FkyAfCGuQZ3O2j1Yg@mail.gmail.com> (raw)
In-Reply-To: <20190430180111.10688-1-mcroce@redhat.com>
On Tue, Apr 30, 2019 at 11:01 AM Matteo Croce <mcroce@redhat.com> wrote:
>
> In the sysctl code the proc_dointvec_minmax() function is often used to
> validate the user supplied value between an allowed range. This function
> uses the extra1 and extra2 members from struct ctl_table as minimum and
> maximum allowed value.
>
> On sysctl handler declaration, in every source file there are some readonly
> variables containing just an integer which address is assigned to the
> extra1 and extra2 members, so the sysctl range is enforced.
>
> The special values 0, 1 and INT_MAX are very often used as range boundary,
> leading duplication of variables like zero=0, one=1, int_max=INT_MAX in
> different source files:
>
> $ git grep -E '\.extra[12].*&(zero|one|int_max)\b' |wc -l
> 248
>
> Add a const int array containing the most commonly used values,
> some macros to refer more easily to the correct array member,
> and use them instead of creating a local one for every object file.
>
> This is the bloat-o-meter output comparing the old and new binary
> compiled with the default Fedora config:
>
> # scripts/bloat-o-meter -d vmlinux.o.old vmlinux.o
> add/remove: 2/2 grow/shrink: 0/2 up/down: 24/-188 (-164)
> Data old new delta
> sysctl_vals - 12 +12
> __kstrtab_sysctl_vals - 12 +12
> max 14 10 -4
> int_max 16 - -16
> one 68 - -68
> zero 128 28 -100
> Total: Before=20583249, After=20583085, chg -0.00%
>
> Signed-off-by: Matteo Croce <mcroce@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2019-04-30 18:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-30 18:01 [PATCH v5] proc/sysctl: add shared variables for range check Matteo Croce
2019-04-30 18:14 ` Kees Cook [this message]
2019-05-16 16:09 ` Matteo Croce
2019-05-16 18:33 ` Kees Cook
2019-05-23 8:05 ` Aaron Tomlin
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