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

[Dag Moxnes]

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()
> >    rdma_resolve_ip()
> >      addr_resolve()
> >        addr_resolve_neigh()
> >          fetch_ha()
> >            dst_fetch_ha()
> >              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.
>
> >   drivers/infiniband/core/addr.c | 9 ++++++---
> >   1 file changed, 6 insertions(+), 3 deletions(-)
> Applied to for-next, thanks
>
> Jason