Re: [PATCH v3] RDMA/core: Fix race when resolving IP address

[Dag Moxnes]

Den 08.07.2019 21:38, skrev Jason Gunthorpe:
> On Mon, Jul 08, 2019 at 07:22:45PM +0000, Mark Bloch wrote:
> > On 7/8/19 11:47 AM, Dag Moxnes wrote:
> > > Thanks Jason,
> > >
> > > Regards,
> > > Dag
> > >
> > > Den 08.07.2019 19:50, skrev Jason Gunthorpe:
> > > > On Mon, Jul 08, 2019 at 01:16:24PM +0200, Dag Moxnes wrote:
> > > > > Use neighbour lock when copying MAC address from neighbour data struct
> > > > > in dst_fetch_ha.
> > > > >
> > > > > When not using the lock, it is possible for the function to race with
> > > > > neigh_update, causing it to copy an invalid MAC address.
> > > > >
> > > > > It is possible to provoke this error by calling rdma_resolve_addr in a
> > > > > tight loop, while deleting the corresponding ARP entry in another tight
> > > > > loop.
> > > > >
> > > > > This will cause the race shown it the following sample trace:
> > > > >
> > > > > rdma_resolve_addr()
> > > > >  ÂÂ rdma_resolve_ip()
> > > > >  ÂÂÂÂ addr_resolve()
> > > > >  ÂÂÂÂÂÂ addr_resolve_neigh()
> > > > >  ÂÂÂÂÂÂÂÂ fetch_ha()
> > > > >  ÂÂÂÂÂÂÂÂÂÂ dst_fetch_ha()
> > > > >  ÂÂÂÂÂÂÂÂÂÂÂÂ n->nud_state == NUD_VALID
> > > > It isn't nud_state that is the problem here, it is the parallel
> > > > memcpy's onto ha. I fixed the commit message
> > > >
> > > > This could also have been solved by using the ha_lock, but I don't
> > > > think we have a reason to particularly over-optimize this.
> > Sorry I'm late to the party, but why not just use: neigh_ha_snapshot()?
> Yes, that is much better, please respin this
OK, will do!
Can I still post it as a v4? Or should I do it differently as you 
already applied it?

Regards,
-Dag
> Thanks,
> Jason