Patch "RDMA/rxe: Fix a race condition in rxe_requester()" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

RDMA/rxe: Fix a race condition in rxe_requester()

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rdma-rxe-fix-a-race-condition-in-rxe_requester.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Bart Van Assche <[email protected]>
Date: Fri, 12 Jan 2018 15:11:58 -0800
Subject: RDMA/rxe: Fix a race condition in rxe_requester()

From: Bart Van Assche <[email protected]>

commit 65567e41219888feec72fee1de98ccf1efbbc16d upstream.

The rxe driver works as follows:
* The send queue, receive queue and completion queues are implemented as circular buffers.
* ib_post_send() and ib_post_recv() calls are serialized through a spinlock.
* Removing elements from various queues happens from tasklet context. Tasklets are guaranteed to run on at most one CPU. This serializes access to these queues. See also rxe_completer(), rxe_requester() and rxe_responder().
* rxe_completer() processes the skbs queued onto qp->resp_pkts.
* rxe_requester() handles the send queue (qp->sq.queue).
* rxe_responder() processes the skbs queued onto qp->req_pkts.

Since rxe_drain_req_pkts() processes qp->req_pkts, calling rxe_drain_req_pkts() from rxe_requester() is racy. Hence this patch.

---
 drivers/infiniband/sw/rxe/rxe_loc.h  |    1 -
 drivers/infiniband/sw/rxe/rxe_req.c  |    9 +--------
 drivers/infiniband/sw/rxe/rxe_resp.c |    2 +-
 3 files changed, 2 insertions(+), 10 deletions(-)

@@ -237,7 +237,6 @@ int rxe_srq_from_attr(struct rxe_dev *rx
 
 void rxe_release(struct kref *kref);
 
-void rxe_drain_req_pkts(struct rxe_qp *qp, bool notify);
 int rxe_completer(void *arg);
 int rxe_requester(void *arg);
 int rxe_responder(void *arg);

@@ -594,15 +594,8 @@ int rxe_requester(void *arg)
 	rxe_add_ref(qp);
 
 next_wqe:
-	if (unlikely(!qp->valid)) {
-		rxe_drain_req_pkts(qp, true);
+	if (unlikely(!qp->valid || qp->req.state == QP_STATE_ERROR))
 		goto exit;
-	}
-
-	if (unlikely(qp->req.state == QP_STATE_ERROR)) {
-		rxe_drain_req_pkts(qp, true);
-		goto exit;
-	}
 
 	if (unlikely(qp->req.state == QP_STATE_RESET)) {
 		qp->req.wqe_index = consumer_index(qp->sq.queue);

@@ -1210,7 +1210,7 @@ static enum resp_states do_class_d1e_err
 	}
 }
 
-void rxe_drain_req_pkts(struct rxe_qp *qp, bool notify)
+static void rxe_drain_req_pkts(struct rxe_qp *qp, bool notify)
 {
 	struct sk_buff *skb;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/ib-core-fix-two-kernel-warnings-triggered-by-rxe-registration.patch queue-4.15/rdma-rxe-fix-a-race-condition-in-rxe_requester.patch queue-4.15/rdma-rxe-fix-rxe_qp_cleanup.patch queue-4.15/rdma-rxe-fix-a-race-condition-related-to-the-qp-error-state.patch