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Subject[PATCH 5.5 005/120] RDMA/netlink: Do not always generate an ACK for some netlink operations
Date
From: Håkon Bugge <haakon.bugge@oracle.com>

commit a242c36951ecd24bc16086940dbe6b522205c461 upstream.

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@oracle.com
Suggested-by: Mark Haywood <mark.haywood@oracle.com>
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Tested-by: Mark Haywood <mark.haywood@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/core/addr.c | 2 +-
drivers/infiniband/core/sa_query.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -139,7 +139,7 @@ int ib_nl_handle_ip_res_resp(struct sk_b
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,
--- a/drivers/infiniband/core/sa_query.c
+++ b/drivers/infiniband/core/sa_query.c
@@ -1068,7 +1068,7 @@ int ib_nl_handle_set_timeout(struct sk_b
}

settimeout_out:
- return skb->len;
+ return 0;
}

static inline int ib_nl_is_good_resolve_resp(const struct nlmsghdr *nlh)
@@ -1139,7 +1139,7 @@ int ib_nl_handle_resolve_resp(struct sk_
}

resp_out:
- return skb->len;
+ return 0;
}

static void free_sm_ah(struct kref *kref)

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