[dpdk-stable] patch 'vhost: fix double read of descriptor flags' 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 12/18/18. 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 162166cae7ce59efb5b7086ad6837143ab5e5298 Mon Sep 17 00:00:00 2001
From: Ilya Maximets <i.maximets at samsung.com>
Date: Wed, 5 Dec 2018 18:09:26 +0300
Subject: [PATCH] vhost: fix double read of descriptor flags

[ upstream commit 48cae0bfa60c451c5d9c0d5be932300aadc7e676 ]

Flags could be updated in a separate process leading to the
inconsistent check.

Additionally, read marked as 'volatile' to highlight the shared
nature of the variable and avoid such issues in the future.

Fixes: d3211c98c456 ("vhost: add helpers for packed virtqueues")

Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 lib/librte_vhost/vhost.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 9ac607bad..bdbea68d2 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -385,6 +385,8 @@ static inline bool
 desc_is_avail(struct vring_packed_desc *desc, bool wrap_counter)
 {
-	return wrap_counter == !!(desc->flags & VRING_DESC_F_AVAIL) &&
-		wrap_counter != !!(desc->flags & VRING_DESC_F_USED);
+	uint16_t flags = *((volatile uint16_t *) &desc->flags);
+
+	return wrap_counter == !!(flags & VRING_DESC_F_AVAIL) &&
+		wrap_counter != !!(flags & VRING_DESC_F_USED);
 }
 
-- 
2.19.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2018-12-14 17:49:48.190692519 +0000
+++ 0017-vhost-fix-double-read-of-descriptor-flags.patch	2018-12-14 17:49:47.000000000 +0000
@@ -1,8 +1,10 @@
-From 48cae0bfa60c451c5d9c0d5be932300aadc7e676 Mon Sep 17 00:00:00 2001
+From 162166cae7ce59efb5b7086ad6837143ab5e5298 Mon Sep 17 00:00:00 2001
 From: Ilya Maximets <i.maximets at samsung.com>
 Date: Wed, 5 Dec 2018 18:09:26 +0300
 Subject: [PATCH] vhost: fix double read of descriptor flags
 
+[ upstream commit 48cae0bfa60c451c5d9c0d5be932300aadc7e676 ]
+
 Flags could be updated in a separate process leading to the
 inconsistent check.
 
@@ -10,7 +12,6 @@
 nature of the variable and avoid such issues in the future.
 
 Fixes: d3211c98c456 ("vhost: add helpers for packed virtqueues")
-Cc: stable at dpdk.org
 
 Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
 Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
@@ -19,10 +20,10 @@
  1 file changed, 4 insertions(+), 2 deletions(-)
 
 diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
-index 5218f1b12..552b9298d 100644
+index 9ac607bad..bdbea68d2 100644
 --- a/lib/librte_vhost/vhost.h
 +++ b/lib/librte_vhost/vhost.h
-@@ -394,6 +394,8 @@ static inline bool
+@@ -385,6 +385,8 @@ static inline bool
  desc_is_avail(struct vring_packed_desc *desc, bool wrap_counter)
  {
 -	return wrap_counter == !!(desc->flags & VRING_DESC_F_AVAIL) &&