[PATCH AUTOSEL 4.9 011/141] RDMA/netlink: Do not always generate an ACK for some netlink operations

[Sasha Levin]

From: HÃkon Bugge <haakon.bugge@xxxxxxxxxx>

[ Upstream commit a242c36951ecd24bc16086940dbe6b522205c461 ]

In rdma_nl_rcv_skb(), the local variable err is assigned the return value
of the supplied callback function, which could be one of
ib_nl_handle_resolve_resp(), ib_nl_handle_set_timeout(), or
ib_nl_handle_ip_res_resp(). These three functions all return skb->len on
success.

rdma_nl_rcv_skb() is merely a copy of netlink_rcv_skb(). The callback
functions used by the latter have the convention: "Returns 0 on success or
a negative error code".

In particular, the statement (equal for both functions):

   if (nlh->nlmsg_flags & NLM_F_ACK || err)

implies that rdma_nl_rcv_skb() always will ack a message, independent of
the NLM_F_ACK being set in nlmsg_flags or not.

The fix could be to change the above statement, but it is better to keep
the two *_rcv_skb() functions equal in this respect and instead change the
three callback functions in the rdma subsystem to the correct convention.

Fixes: 2ca546b92a02 ("IB/sa: Route SA pathrecord query through netlink")
Fixes: ae43f8286730 ("IB/core: Add IP to GID netlink offload")
Link: https://lore.kernel.org/r/20191216120436.3204814-1-haakon.bugge@xxxxxxxxxx
Suggested-by: Mark Haywood <mark.haywood@xxxxxxxxxx>
Signed-off-by: HÃkon Bugge <haakon.bugge@xxxxxxxxxx>
Tested-by: Mark Haywood <mark.haywood@xxxxxxxxxx>
Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/core/addr.c     | 2 +-
 drivers/infiniband/core/sa_query.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
index 1baa25e82bdd9..f7d23c1081dc4 100644
--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -141,7 +141,7 @@ int ib_nl_handle_ip_res_resp(struct sk_buff *skb,
 	if (ib_nl_is_good_ip_resp(nlh))
 		ib_nl_process_good_ip_rsep(nlh);
 
-	return skb->len;
+	return 0;
 }
 
 static int ib_nl_ip_send_msg(struct rdma_dev_addr *dev_addr,
diff --git a/drivers/infiniband/core/sa_query.c b/drivers/infiniband/core/sa_query.c
index 5879a06ada938..1c459725d64e7 100644
--- a/drivers/infiniband/core/sa_query.c
+++ b/drivers/infiniband/core/sa_query.c
@@ -848,7 +848,7 @@ int ib_nl_handle_set_timeout(struct sk_buff *skb,
 	}
 
 settimeout_out:
-	return skb->len;
+	return 0;
 }
 
 static inline int ib_nl_is_good_resolve_resp(const struct nlmsghdr *nlh)
@@ -920,7 +920,7 @@ int ib_nl_handle_resolve_resp(struct sk_buff *skb,
 	}
 
 resp_out:
-	return skb->len;
+	return 0;
 }
 
 static void free_sm_ah(struct kref *kref)
-- 
2.20.1