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Subject[PATCH v2] RDMA/core: Fix race when resolving IP address
Date
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
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