On Fri, May 12, 2017 at 05:33:36PM +0300, Kirill Tkhai wrote: > During checkpointing and restore of userspace tasks > we bumped into the situation, that it's not possible > to restore the tasks, which user namespace does not > have uid 0 or gid 0 mapped. > > People create user namespace mappings like they want, > and there is no a limitation on obligatory uid and gid > "must be mapped". So, if there is no uid 0 or gid 0 > in the mapping, it's impossible to restore mm->exe_file > of the processes belonging to this user namespace. > > Also, there is no a workaround. It's impossible > to create a temporary uid/gid mapping, because > only one write to /proc/[pid]/uid_map and gid_map > is allowed during a namespace lifetime. > If there is an entry, then no more mapings can't be > written. If there isn't an entry, we can't write > there too, otherwise user task won't be able > to do that in the future. > > The patch changes the check, and looks for CAP_SYS_ADMIN > instead of zero uid and gid. This allows to restore > a task independently of its user namespace mappings. > > Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com> > CC: Andrew Morton <a...@linux-foundation.org> > CC: Serge Hallyn <se...@hallyn.com> > CC: "Eric W. Biederman" <ebied...@xmission.com> > CC: Oleg Nesterov <o...@redhat.com> > CC: Michal Hocko <mho...@suse.com> > CC: Andrei Vagin <ava...@openvz.org> > CC: Cyrill Gorcunov <gorcu...@openvz.org> > CC: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> > CC: Pavel Tikhomirov <ptikhomi...@virtuozzo.com> > --- > kernel/sys.c | 8 ++------ > 1 file changed, 2 insertions(+), 6 deletions(-)
Reviewed-by: Cyrill Gorcunov <gorcu...@openvz.org>
