[PATCH rdma-next 3/3] RDMA/core: Reject LAG selection when source MAC lookup fails

[Leon Romanovsky <leon@kernel.org>]

From: Leon Romanovsky <leonro@nvidia.com>

GID deletion can clear the source device association after LAG lookup
retains the bonding master. Ignoring the resulting L2 lookup failure
copies uninitialized source MAC bytes into the synthetic hash packet.

Read the source MAC before allocating the packet and propagate lookup
errors to the caller, so failed lookups cannot influence slave selection.

Fixes: bd3920eac133 ("RDMA/core: Add LAG functionality")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/infiniband/core/lag.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/core/lag.c b/drivers/infiniband/core/lag.c
index 88aac911e8ee..651c868aa04e 100644
--- a/drivers/infiniband/core/lag.c
+++ b/drivers/infiniband/core/lag.c
@@ -19,6 +19,11 @@ static struct sk_buff *rdma_build_skb(struct net_device *netdev,
 	u8 smac[ETH_ALEN];
 	bool is_ipv4;
 	int hdr_len;
+	int ret;
+
+	ret = rdma_read_gid_l2_fields(ah_attr->grh.sgid_attr, NULL, smac);
+	if (ret)
+		return ERR_PTR(ret);
 
 	is_ipv4 = ipv6_addr_v4mapped((struct in6_addr *)ah_attr->grh.dgid.raw);
 	hdr_len = ETH_HLEN + sizeof(struct udphdr) + LL_RESERVED_SPACE(netdev);
@@ -26,7 +31,7 @@ static struct sk_buff *rdma_build_skb(struct net_device *netdev,
 
 	skb = alloc_skb(hdr_len, flags);
 	if (!skb)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	skb->dev = netdev;
 	skb_reserve(skb, hdr_len);
@@ -70,7 +75,6 @@ static struct sk_buff *rdma_build_skb(struct net_device *netdev,
 	skb_reset_mac_header(skb);
 	eth = eth_hdr(skb);
 	skb->protocol = eth->h_proto = htons(is_ipv4 ? ETH_P_IP : ETH_P_IPV6);
-	rdma_read_gid_l2_fields(ah_attr->grh.sgid_attr, NULL, smac);
 	memcpy(eth->h_source, smac, ETH_ALEN);
 	memcpy(eth->h_dest, ah_attr->roce.dmac, ETH_ALEN);
 
@@ -86,8 +90,8 @@ static struct net_device *rdma_get_xmit_slave_udp(struct ib_device *device,
 	struct sk_buff *skb;
 
 	skb = rdma_build_skb(master, ah_attr, flags);
-	if (!skb)
-		return ERR_PTR(-ENOMEM);
+	if (IS_ERR(skb))
+		return ERR_CAST(skb);
 
 	rcu_read_lock();
 	slave = netdev_get_xmit_slave(master, skb,

-- 
2.55.0