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Subject: Re: [PATCH] proc: pid/status: show all supplementary groups
From: Kees Cook <keescook@chromium.org>
To: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        linux-kernel@vger.kernel.org
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On Fri, Nov 9, 2012 at 5:31 AM, Artem Bityutskiy <dedekind1@gmail.com> wrote:
> From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
>
> We display a list of supplementary group for each process in the
> /proc/<pid>/status. However, we show only the first 32 groups, not all of them.
>
> Although this is rare, but sometimes processes do have more than 32
> supplementary groups, and this kernel limitation breaks user-space apps
> that rely on the group list in /proc/<pid>/status.
>
> Number 32 comes from the internal NGROUPS_SMALL macro which defines the
> length for the internal kernel "small" groups buffer. There is no apparent
> reason to limit to this value.
>
> This patch removes the 32 groups printing limit.
>
> The Linux kernel limits the amount of supplementary groups by NGROUPS_MAX,
> which is currently set to 65536. And this is the maximum count of groups we
> may possibly print.
>
> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Acked-by: Kees Cook <keescook@chromium.org>

> Cc: stable@vger.kernel.org
> ---
>  fs/proc/array.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> NOTE: I consider this to be a bug which breaks user-space, so I add -stable.

I'm not sure if this will fly since it's been broken for a very long
time, but it's a tiny change.

-Kees

-- 
Kees Cook
Chrome OS Security
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