Thanks. I will submit a patch.
Baptiste.
On Thu, Jan 7, 2021 at 3:57 PM Willem de Bruijn
<willemdebruijn.ker...@gmail.com> wrote:
>
> On Wed, Jan 6, 2021 at 10:54 PM Baptiste Lepers
> <baptiste.lep...@gmail.com> wrote:
> >
> > Hello,
> >
> > While reading the code of net/core/sock_reuseport.c, I think I found a
> > possible race in reuseport_select_sock. The current code has the
> > following pattern:
> >
> > socks = READ_ONCE(reuse->num_socks);
> > smp_rmb(); // paired with reuseport_add_sock to make sure
> > reuse->socks[i < num_socks] are initialized
> > while (reuse->socks[i]->sk_state == TCP_ESTABLISHED) {
> > if (i >= reuse->num_socks) // should be "socks" and not
> > "reuse->num_socks"?
> >
> > The barrier seems to be here to make sure that all items of
> > reuse->socks are initialized before being read, but the barrier only
> > protects indexes < socks, not indexes < reuse->num_socks.
> >
> > I have a patch ready to fix this issue, but I wanted to confirm that
> > the current code is indeed incorrect (if the code is correct for a
> > non-obvious reason, I'd be happy to add some comments to document the
> > behavior).
> >
> >
> > Here is the diff of the patch I was planning to submit:
> >
> > diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
> > index bbdd3c7b6cb5..b065f0a103ed 100644
> > --- a/net/core/sock_reuseport.c
> > +++ b/net/core/sock_reuseport.c
> > @@ -293,7 +293,7 @@ struct sock *reuseport_select_sock(struct sock *sk,
> > i = j = reciprocal_scale(hash, socks);
> > while (reuse->socks[i]->sk_state == TCP_ESTABLISHED) {
> > i++;
> > - if (i >= reuse->num_socks)
> > + if (i >= socks)
> > i = 0;
> > if (i == j)
> > goto out;
> >
> >
> > Thanks,
> > Baptiste.
>
> Thanks for the clear description. Yes, I believe you're correct.
