[CRIU] [PATCH] mount: close mnt.ns_fd only for sub-namespaces (v2)

[Andrew Vagin]

On Thu, Nov 26, 2015 at 05:11:56PM +0300, Pavel Emelyanov wrote:
> On 11/26/2015 05:02 PM, Andrey Vagin wrote:
> > From: Andrew Vagin <avagin at virtuozzo.com>
> > 
> > nsid->mnt.ns_fd is initialized into 0, so currently
> > fini_restore_mntns() closes the 0 descriptor if processes
> > lives in a current mount namespace (NS_CRIU).
> > 
> > Without this patch I get the following error:
> > (00.166444)   4109: Inherit fd tty:[8800:d] -> 0 has been closed
> > 
> > v2: typo fix
> > Signed-off-by: Andrew Vagin <avagin at virtuozzo.com>
> > ---
> >  mount.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/mount.c b/mount.c
> > index 20ae79b..d0f05f6 100644
> > --- a/mount.c
> > +++ b/mount.c
> > @@ -2653,7 +2653,7 @@ void fini_restore_mntns(void)
> >  	for (nsid = ns_ids; nsid != NULL; nsid = nsid->next) {
> >  		if (nsid->nd != &mnt_ns_desc)
> >  			continue;
> > -		if (root_item->ids->mnt_ns_id == nsid->id)
> > +		if (nsid->type != NS_OTHER)
> >  			continue;
> >  		close(nsid->mnt.ns_fd);
> 
> Look at prepare_mnt_ns() it does this:

It calls rst_collect_local_mntns(), which allocates ns_id for criu mount
namespaces.

        if (!(root_ns_mask & CLONE_NEWNS))
                return rst_collect_local_mntns();
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> 
>        for (nsid = ns_ids; nsid != NULL; nsid = nsid->next) {
>                 char path[PATH_MAX];
> 
>                 if (nsid->nd != &mnt_ns_desc)
>                         continue;
>                 if (root_item->ids->mnt_ns_id == nsid->id)
>                         continue;

We skip the root mount namespace ^^^^

> 
> 		...
> 
> 		nsid->mnt.ns_fd = open_proc(PROC_SELF, "ns/mnt");
>                 if (nsid->mnt.ns_fd < 0)
>                         goto err;
> 
> There's no single check for nsid->type, why do we have one on
> the closing part?



> 
> >  	}
> > 
>