On Fri, Oct 20, 2017 at 05:06:47PM +0100, Gargi Sharma wrote:
> On Thu, Oct 19, 2017 at 5:18 PM, Oleg Nesterov <[email protected]> wrote:
> > On 10/19, Andrei Vagin wrote:
> >>
> >> Hi Gargi,
> >>
> >> This patch breaks CRIU, because it changes a meaning of ns_last_pid.
> >
> > ...
> >
> >> > @@ -311,7 +297,7 @@ static int pid_ns_ctl_handler(struct ctl_table
> >> > *table, int write,
> >> > * it should synchronize its usage with external means.
> >> > */
> >> >
> >> > - tmp.data = &pid_ns->last_pid;
> >> > + tmp.data = &pid_ns->idr.idr_next;
> >
> > Ah, yes, off-by-one error...
> >
> > Gargi, I don't think you need to make another version, I'd suggest you to
> > send
> > the trivial fix to Andrew, afaics you just need to replace these 2 lines
> > with
> >
> > unsigned int last;
> > int err;
> >
> > tmp.data = &last;
> > err = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
> > if (!err)
> > idr_set_cursor(&pid_ns->idr, last + 1);
> > return err;
> I'm not sure entirely understand how this takes care of rolling over of PIDs?
> Can we ignore that? If yes, won't the tests for CRIU still break?
Gargi, I don't understand what you mean. Could you elaborate? Do you
mean a case when idr_next is bigger than pid_max? I think this logic
remains the same what we had before switching to idr.
CRIU tests works with a following patch. It is slightly modified version
of Oleg's patch.
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index fea2c24..1c791b3 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -287,6 +287,7 @@ static int pid_ns_ctl_handler(struct ctl_table
*table, int write,
{
struct pid_namespace *pid_ns = task_active_pid_ns(current);
struct ctl_table tmp = *table;
+ int ret;
if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
return -EPERM;
@@ -298,7 +299,12 @@ static int pid_ns_ctl_handler(struct ctl_table
*table, int write,
*/
tmp.data = &pid_ns->idr.idr_next;
- return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+ ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+ if (ret < 0)
+ return ret;
+
+ idr_set_cursor(&pid_ns->idr, pid_ns->idr.idr_next + 1);
+ return 0;
}
extern int pid_max;
>
> Thanks,
> Gargi
> >
> > Oleg.
> >
