[PATCH 3.16 090/305] IB/cm: Avoid AV ah_attr overwriting during LAP message handling

[Ben Hutchings]

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Parav Pandit <parav@xxxxxxxxxxxx>

commit a5c57d327272bdf3a8b19686eaca2ec683449e67 upstream.

AH attribute of the cm_id can be overwritten if LAP message is received
on CM request which is in progress. This bug got introduced to avoid
sleeping when spin lock is held as part of commit in Fixes tag.

Therefore validate the cm_id state first and continue to perform AV
ah_attr initialization.

Given that Aleternative path related messages are not supported for
RoCE, init_av_from_response/path is such messages are ok to be called
from blocking context.

Fixes: 33f93e1ebcf5 ("IB/cm: Fix sleeping while spin lock is held")
Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/infiniband/core/cm.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -2770,12 +2770,6 @@ static int cm_lap_handler(struct cm_work
 	if (!cm_id_priv)
 		return -EINVAL;
 
-	ret = cm_init_av_for_response(work->port, work->mad_recv_wc->wc,
-				      work->mad_recv_wc->recv_buf.grh,
-				      &cm_id_priv->av);
-	if (ret)
-		goto deref;
-
 	param = &work->cm_event.param.lap_rcvd;
 	param->alternate_path = &work->path[0];
 	cm_format_path_from_lap(cm_id_priv, param->alternate_path, lap_msg);
@@ -2813,10 +2807,16 @@ static int cm_lap_handler(struct cm_work
 		goto unlock;
 	}
 
-	cm_id_priv->id.lap_state = IB_CM_LAP_RCVD;
-	cm_id_priv->tid = lap_msg->hdr.tid;
+	ret = cm_init_av_for_response(work->port, work->mad_recv_wc->wc,
+				      work->mad_recv_wc->recv_buf.grh,
+				      &cm_id_priv->av);
+	if (ret)
+		goto unlock;
+
 	cm_init_av_by_path(param->alternate_path, &cm_id_priv->alt_av,
 			   cm_id_priv);
+	cm_id_priv->id.lap_state = IB_CM_LAP_RCVD;
+	cm_id_priv->tid = lap_msg->hdr.tid;
 	ret = atomic_inc_and_test(&cm_id_priv->work_count);
 	if (!ret)
 		list_add_tail(&work->list, &cm_id_priv->work_list);