Re: [BUG] Bug in netprio_cgroup and netcls_cgroup ?

[Daniel Wagner]

On 23.01.2013 01:02, John Fastabend wrote:
> [...]
>
> > > OK, I guess we should do something similar in the netprio, netcls
> > > cgroups and
> > > yes document it as you noted in your last comment.
> >
> > Here is my attempt to add such a check. I really don't know if this is
> > the
> > correct way to do so. To test this I have written a test program, which
> > seems to test the right thing. Please have a look and let me know if
> > it is correct: http://www.monom.org/misc/scm_rights.c
> >
> > And here a dirty first version of the patch:
> >
> >
> >  From 49a78d907eaf31c16673025e7e3b4844e419e416 Mon Sep 17 00:00:00 2001
> > From: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
> > Date: Tue, 22 Jan 2013 11:08:22 +0100
> > Subject: [PATCH] net: net_prio: Block attach if a socket is shared
> >
> > ---
> >   net/core/netprio_cgroup.c | 30 ++++++++++++++++++++++++++++++
> >   1 file changed, 30 insertions(+)
> >
> > diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> > index 847c02b..de4e6c5 100644
> > --- a/net/core/netprio_cgroup.c
> > +++ b/net/core/netprio_cgroup.c
> > @@ -274,9 +274,39 @@ static struct cftype ss_files[] = {
> >       { }    /* terminate */
> >   };
> >
> > +static int check_cnt(const void *v, struct file *file, unsigned n)
> > +{
> > +    unsigned *flag = (unsigned *)v;
> > +    int err;
> > +
> > +    struct socket *sock = sock_from_file(file, &err);
> > +    if (sock && file_count(file) > 1)
> > +        *flag = 1;
> > +
>
> I think this check will catch a lot of cases that are not necessarily
> sharing a socket across tasks though. For example iscsid passes a file
> descriptor to the kernel which does a sockfd_lookup() incrementing
> f_count. Similarly look at dup/clone/etc.

Yep, I expected that this patch was too simple.

> In many of these cases I believe it should be OK to move the task
> around when the sockets are not shared between multiple tasks.

Do you know of a different way to identify the shared sockets?

thanks,
daniel

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