iw_cxgb4: add referencing to wait objects

For messages sent from the host to fw that solicit a reply from fw,
the c4iw_wr_wait struct pointer is passed in the host->fw message, and
included in the fw->host fw6_msg reply.  This allows the sender to wait
until the reply is received, and the code processing the ingress reply
to wake up the sender.

If c4iw_wait_for_reply() times out, however, we need to keep the
c4iw_wr_wait object around in case the reply eventually does arrive.
Otherwise we have touch-after-free bugs in the wake_up paths.

This was hit due to a bad kernel driver that blocked ingress processing
of cxgb4 for a long time, causing iw_cxgb4 timeouts, but eventually
resuming ingress processing and thus hitting the touch-after-free bug.

So I want to fix iw_cxgb4 such that we'll at least keep the wait object
around until the reply comes.  If it never comes we leak a small amount of
memory, but if it does come late, we won't potentially crash the system.

So add a kref struct in the c4iw_wr_wait struct, and take a reference
before sending a message to FW that will generate a FW6 reply.  And remove
the reference (and potentially free the wait object) when the reply
is processed.

The ep code also uses the wr_wait for non FW6 CPL messages and doesn't
embed the c4iw_wr_wait object in the message sent to firmware.  So for
those cases we add c4iw_wake_up_noref().

The mr/mw, cq, and qp object create/destroy paths do need this reference
logic.  For these paths, c4iw_ref_send_wait() is introduced to take the
wr_wait reference, send the msg to fw, and then wait for the reply.

So going forward, iw_cxgb4 either uses c4iw_ofld_send(),
c4iw_wait_for_reply() and c4iw_wake_up_noref() like is done in the some
of the endpoint logic, or c4iw_ref_send_wait() and c4iw_wake_up_deref()
(formerly c4iw_wake_up()) when sending messages with the c4iw_wr_wait
object pointer embedded in the message and resulting FW6 reply.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/infiniband/hw/cxgb4/device.c b/drivers/infiniband/hw/cxgb4/device.c
index d19f7fb2966c..fa16a4a8c9a4 100644
--- a/drivers/infiniband/hw/cxgb4/device.c
+++ b/drivers/infiniband/hw/cxgb4/device.c
@@ -1518,6 +1518,27 @@ static struct cxgb4_uld_info c4iw_uld_info = {
 	.control = c4iw_uld_control,
 };
 
+void _c4iw_free_wr_wait(struct kref *kref)
+{
+	struct c4iw_wr_wait *wr_waitp;
+
+	wr_waitp = container_of(kref, struct c4iw_wr_wait, kref);
+	pr_debug("Free wr_wait %p\n", wr_waitp);
+	kfree(wr_waitp);
+}
+
+struct c4iw_wr_wait *c4iw_alloc_wr_wait(gfp_t gfp)
+{
+	struct c4iw_wr_wait *wr_waitp;
+
+	wr_waitp = kzalloc(sizeof(*wr_waitp), gfp);
+	if (wr_waitp) {
+		kref_init(&wr_waitp->kref);
+		pr_debug("wr_wait %p\n", wr_waitp);
+	}
+	return wr_waitp;
+}
+
 static int __init c4iw_init_module(void)
 {
 	int err;