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

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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




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