[PATCH AUTOSEL 5.1 107/141] RDMA/core: Fix race when resolving IP address

Sasha Levin
2019-07-19T04:06:23Z

From: Dag Moxnes <dag.moxnes@oracle.com>

[ Upstream commit d8d9ec7dc5abbb3f11d866e983c4984f5c2de9d6 ]

Use the neighbour lock when copying the MAC address from the 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 torn MAC address:

rdma_resolve_addr()
rdma_resolve_ip()
addr_resolve()
addr_resolve_neigh()
fetch_ha()
dst_fetch_ha()
memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN)

and

net_ioctl()
arp_ioctl()
arp_rec_delete()
arp_invalidate()
neigh_update()
__neigh_update()
memcpy(&neigh->ha, lladdr, dev->addr_len)

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.

Fixes: 51d45974515c ("infiniband: addr: Consolidate code to fetch neighbour hardware address from dst.")
Signed-off-by: Dag Moxnes <dag.moxnes@oracle.com>
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/core/addr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
index d0b04b0d309f..4ca31ce29a29 100644
--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -336,7 +336,7 @@ static int dst_fetch_ha(const struct dst_entry *dst,
neigh_event_send(n, NULL);
ret = -ENODATA;
} else {
- memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
+ neigh_ha_snapshot(dev_addr->dst_dev_addr, n, dst->dev);
}

neigh_release(n);
--
2.20.1