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 [off-list ref] wrote:
(...)

quoted

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/