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SubjectRe: [PATCH] proc: pid/status: show all supplementary groups
Quoting Artem Bityutskiy (dedekind1@gmail.com):
> 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>

The 'min' is older than git history, but at that dawn of time the code
was just sprintf()ing into a large buffer.

I don't *really* see a problem with this, though if someone did have 1000
groups /proc/$$/status would be sort of annoying to read. So on the one
hand adding a '...' in /proc/self/status after 32, and adding a /proc/$$/creds
file seems more pleasant, but then you get into the whole adding files to
/proc kerfuffle, so...

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

> 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.
>
> diff --git a/fs/proc/array.c b/fs/proc/array.c
> index c1c207c..bd31e02 100644
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -212,7 +212,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
> group_info = cred->group_info;
> task_unlock(p);
>
> - for (g = 0; g < min(group_info->ngroups, NGROUPS_SMALL); g++)
> + for (g = 0; g < group_info->ngroups; g++)
> seq_printf(m, "%d ",
> from_kgid_munged(user_ns, GROUP_AT(group_info, g)));
> put_cred(cred);
> --
> 1.7.7.6
>


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