[dpdk-stable] patch 'ipc: fix access after async request failure' has been queued to stable release 18.08.1

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 18.08.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 12/08/18. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the patch applied
to the branch. If the code is different (ie: not only metadata diffs), due for example to
a change in context or macro names, please double check it.

Thanks.

Kevin Traynor

---
>From 4f8eb35337f7778d64297863c8a6c5407a17f4f1 Mon Sep 17 00:00:00 2001
From: Anatoly Burakov <anatoly.burakov at intel.com>
Date: Tue, 20 Nov 2018 16:18:46 +0000
Subject: [PATCH] ipc: fix access after async request failure

[ upstream commit 615fcf55d24eeb3747b3300b25f61eed8f9053ab ]

Previous fix for rte_panic has moved setting of alarm before
sending the message. This means that whether we send a message,
the alarm would still trigger. The comment noted that cleanup
would happen in the alarm handler, but that's not what actually
happened - instead, in the event of failed send we freed the
memory in-place, before putting the request on the queue.

This works OK when the message is sent, but when sending the
message fails, the alarm would still trigger with a pointer
argument that points to non-existent memory, and cause
memory corruption.

There probably is a "proper" fix for this issue, with correct
handling of sent vs. unsent requests, however it would be
simpler just to sacrifice the sent request in the (extremely
unlikely) event of alarm set failing. The other process would
still send a response, but it will be ignored by the sender.

Fixes: 45e5f49e87fb ("ipc: remove panic in async request")

Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
---
 lib/librte_eal/common/eal_common_proc.c | 40 ++++++++-----------------
 1 file changed, 13 insertions(+), 27 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_proc.c b/lib/librte_eal/common/eal_common_proc.c
index f65ef56c0..1c3f09aad 100644
--- a/lib/librte_eal/common/eal_common_proc.c
+++ b/lib/librte_eal/common/eal_common_proc.c
@@ -828,18 +828,17 @@ mp_request_async(const char *dst, struct rte_mp_msg *req,
 	}
 
-	/*
-	 * set the alarm before sending message. there are two possible error
-	 * scenarios to consider here:
-	 *
-	 * - if the alarm set fails, we free the memory right there
-	 * - if the alarm set succeeds but sending message fails, then the alarm
-	 *   will trigger and clean up the memory
-	 *
-	 * Even if the alarm triggers too early (i.e. immediately), we're still
-	 * holding the lock to pending requests queue, so the interrupt thread
-	 * will just spin until we release the lock, and either release the
-	 * memory, or doesn't find any pending requests in the queue because we
-	 * never added any due to send message failure.
-	 */
+	ret = send_msg(dst, req, MP_REQ);
+	if (ret < 0) {
+		RTE_LOG(ERR, EAL, "Fail to send request %s:%s\n",
+			dst, req->name);
+		ret = -1;
+		goto fail;
+	} else if (ret == 0) {
+		ret = 0;
+		goto fail;
+	}
+	param->user_reply.nb_sent++;
+
+	/* if alarm set fails, we simply ignore the reply */
 	if (rte_eal_alarm_set(ts->tv_sec * 1000000 + ts->tv_nsec / 1000,
 			      async_reply_handle, pending_req) < 0) {
@@ -849,19 +848,6 @@ mp_request_async(const char *dst, struct rte_mp_msg *req,
 		goto fail;
 	}
-
-	ret = send_msg(dst, req, MP_REQ);
-	if (ret < 0) {
-		RTE_LOG(ERR, EAL, "Fail to send request %s:%s\n",
-			dst, req->name);
-		ret = -1;
-		goto fail;
-	} else if (ret == 0) {
-		ret = 0;
-		goto fail;
-	}
 	TAILQ_INSERT_TAIL(&pending_requests.requests, pending_req, next);
 
-	param->user_reply.nb_sent++;
-
 	return 0;
 fail:
-- 
2.19.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2018-11-29 13:11:36.758587857 +0000
+++ 0068-ipc-fix-access-after-async-request-failure.patch	2018-11-29 13:11:34.000000000 +0000
@@ -1,8 +1,10 @@
-From 615fcf55d24eeb3747b3300b25f61eed8f9053ab Mon Sep 17 00:00:00 2001
+From 4f8eb35337f7778d64297863c8a6c5407a17f4f1 Mon Sep 17 00:00:00 2001
 From: Anatoly Burakov <anatoly.burakov at intel.com>
 Date: Tue, 20 Nov 2018 16:18:46 +0000
 Subject: [PATCH] ipc: fix access after async request failure
 
+[ upstream commit 615fcf55d24eeb3747b3300b25f61eed8f9053ab ]
+
 Previous fix for rte_panic has moved setting of alarm before
 sending the message. This means that whether we send a message,
 the alarm would still trigger. The comment noted that cleanup