RDMA/ucma: Discard all events for new connections until accepted
After reporting a new connection request to user space, the rdma_ucm
will discard subsequent events until the user has associated a user
space idenfier with the kernel cm_id. This is needed to avoid
reporting a reject/disconnect event to the user for a request that
they may not have processed.
The user space identifier is set once the user tries to accept the
connection request. However, the following race exists in ucma_accept():
ctx->uid = cmd.uid;
<events may be reported now>
ret = rdma_accept(ctx->cm_id, ...);
Once ctx->uid has been set, new events may be reported to the user.
While the above mentioned race is avoided, there is an issue that the
user _may_ receive a reject/disconnect event if rdma_accept() fails,
depending on when the event is processed. To simplify the use of
rdma_accept(), discard all events unless rdma_accept() succeeds.
This problem was discovered based on questions from Roland Dreier
<roland@purestorage.com>.
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index b37b0c0..5034a87 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -808,9 +808,12 @@
return PTR_ERR(ctx);
if (cmd.conn_param.valid) {
- ctx->uid = cmd.uid;
ucma_copy_conn_param(&conn_param, &cmd.conn_param);
+ mutex_lock(&file->mut);
ret = rdma_accept(ctx->cm_id, &conn_param);
+ if (!ret)
+ ctx->uid = cmd.uid;
+ mutex_unlock(&file->mut);
} else
ret = rdma_accept(ctx->cm_id, NULL);
