Re: [PATCH] groups: don't return unmapped gids in getgroups(2)

[Andy Lutomirski]

On Fri, Feb 17, 2017 at 12:44 AM, Aleksa Sarai <asarai@xxxxxxx> wrote:
>>> One thing overlooked by commit 9cc46516ddf4 ("userns: Add a knob to
>>> disable setgroups on a per user namespace basis") is that because
>>> setgroups(2) no longer works in user namespaces it doesn't make any
>>> sense to be returning weird group IDs that the process cannot do
>>> anything with.
>>
>>

> bool DropPrivileges()
> {
>         /* ... */
>       // Verify that the user isn't still in any supplementary groups

But the user *is* still in a supplementary group.  Your proposed
change would break the intent of this code.