You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
55 lines
1.9 KiB
55 lines
1.9 KiB
From 084b8c2e77f1ac07e4a3a121ff957c49a9379385 Mon Sep 17 00:00:00 2001
|
|
From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com>
|
|
Date: Tue, 3 Nov 2015 16:34:09 +0000
|
|
Subject: [PATCH 4/7] xen-blkback: only read request operation from shared ring
|
|
once
|
|
MIME-Version: 1.0
|
|
Content-Type: text/plain; charset=UTF-8
|
|
Content-Transfer-Encoding: 8bit
|
|
|
|
A compiler may load a switch statement value multiple times, which could
|
|
be bad when the value is in memory shared with the frontend.
|
|
|
|
When converting a non-native request to a native one, ensure that
|
|
src->operation is only loaded once by using READ_ONCE().
|
|
|
|
This is part of XSA155.
|
|
|
|
CC: stable@vger.kernel.org
|
|
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
|
|
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
|
|
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
|
|
---
|
|
drivers/block/xen-blkback/common.h | 8 ++++----
|
|
1 file changed, 4 insertions(+), 4 deletions(-)
|
|
|
|
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
|
|
index 68e87a0..c929ae2 100644
|
|
--- a/drivers/block/xen-blkback/common.h
|
|
+++ b/drivers/block/xen-blkback/common.h
|
|
@@ -408,8 +408,8 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
|
|
struct blkif_x86_32_request *src)
|
|
{
|
|
int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST, j;
|
|
- dst->operation = src->operation;
|
|
- switch (src->operation) {
|
|
+ dst->operation = READ_ONCE(src->operation);
|
|
+ switch (dst->operation) {
|
|
case BLKIF_OP_READ:
|
|
case BLKIF_OP_WRITE:
|
|
case BLKIF_OP_WRITE_BARRIER:
|
|
@@ -456,8 +456,8 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
|
|
struct blkif_x86_64_request *src)
|
|
{
|
|
int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST, j;
|
|
- dst->operation = src->operation;
|
|
- switch (src->operation) {
|
|
+ dst->operation = READ_ONCE(src->operation);
|
|
+ switch (dst->operation) {
|
|
case BLKIF_OP_READ:
|
|
case BLKIF_OP_WRITE:
|
|
case BLKIF_OP_WRITE_BARRIER:
|
|
--
|
|
2.1.0
|
|
|