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SubjectRe: [PATCH v2] RDMA/core: Fix race when resolving IP address
On Fri, Jun 28, 2019 at 2:20 PM Dag Moxnes <dag.moxnes@oracle.com> 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.
>
> Signed-off-by: Dag Moxnes <dag.moxnes@oracle.com>
> Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
>
> ---
> v1 -> v2:
> * Modified implementation to improve readability
> ---
> drivers/infiniband/core/addr.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
> index 2f7d141598..51323ffbc5 100644
> --- a/drivers/infiniband/core/addr.c
> +++ b/drivers/infiniband/core/addr.c
> @@ -333,11 +333,14 @@ static int dst_fetch_ha(const struct dst_entry *dst,
> if (!n)
> return -ENODATA;
>
> - if (!(n->nud_state & NUD_VALID)) {
> + read_lock_bh(&n->lock);
> + if (n->nud_state & NUD_VALID) {
> + memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
> + read_unlock_bh(&n->lock);
> + } else {
> + read_unlock_bh(&n->lock);
> neigh_event_send(n, NULL);
> ret = -ENODATA;
> - } else {
> - memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
> }
>
> neigh_release(n);
> --
> 2.20.1
>
Reviewed-by: Parav Pandit <parav@mellanox.com>

A sample trace such as below in commit message would be good to have.
Or the similar one that you noticed with ARP delete sequence.

neigh_changeaddr()
neigh_flush_dev()
n->nud_state = NUD_NOARP;

Having some issues with office outlook, so replying via gmail.

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