Re: [PATCH 2/2] user_namespaces.7: Update the documention to reflect the fixes for negative groups

["Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>]

On 02/02/2015 10:31 PM, Alban Crequy wrote:
> Hello,
> 
> Thanks for updating the man page.
> 
> On 12 December 2014 at 22:54, Eric W. Biederman <ebiederm@xmission.com> wrote:
> (...)
>> Furthermore to preserve in some form the useful applications that have
>> been setting gid_map without privilege the file /proc/[pid]/setgroups
>> was added to allow disabling setgroups.  With the setgroups system
>> call permanently disabled in a user namespace it again becomes safe to
>> allow writes to gid_map without privilege.
>>
>> Here is my meager attempt to update user_namespaces.7 to reflect these
>> issues.
> 
> The program userns_child_exec.c in user_namespaces.7 should be updated
> to write in /proc/.../setgroups, near the line:
> /* Update the UID and GID maps in the child */
> 
> Otherwise, the example given in the manpage does not work:
> $ ./userns_child_exec -p -m -U -M '0 1000 1' -G '0 1000 1' bash

Thanks, Alban. I've added code to the example to handle /proc/PID/setgroups
(and tested).

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/