55 lines
1.9 KiB
Diff
55 lines
1.9 KiB
Diff
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From 084b8c2e77f1ac07e4a3a121ff957c49a9379385 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com>
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Date: Tue, 3 Nov 2015 16:34:09 +0000
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Subject: [PATCH 4/7] xen-blkback: only read request operation from shared ring
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once
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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A compiler may load a switch statement value multiple times, which could
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be bad when the value is in memory shared with the frontend.
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When converting a non-native request to a native one, ensure that
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src->operation is only loaded once by using READ_ONCE().
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This is part of XSA155.
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CC: stable@vger.kernel.org
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Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
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Signed-off-by: David Vrabel <david.vrabel@citrix.com>
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Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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---
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drivers/block/xen-blkback/common.h | 8 ++++----
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1 file changed, 4 insertions(+), 4 deletions(-)
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diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
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index 68e87a0..c929ae2 100644
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--- a/drivers/block/xen-blkback/common.h
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+++ b/drivers/block/xen-blkback/common.h
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@@ -408,8 +408,8 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
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struct blkif_x86_32_request *src)
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{
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int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST, j;
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- dst->operation = src->operation;
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- switch (src->operation) {
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+ dst->operation = READ_ONCE(src->operation);
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+ switch (dst->operation) {
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case BLKIF_OP_READ:
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case BLKIF_OP_WRITE:
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case BLKIF_OP_WRITE_BARRIER:
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@@ -456,8 +456,8 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
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struct blkif_x86_64_request *src)
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{
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int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST, j;
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- dst->operation = src->operation;
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- switch (src->operation) {
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+ dst->operation = READ_ONCE(src->operation);
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+ switch (dst->operation) {
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case BLKIF_OP_READ:
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case BLKIF_OP_WRITE:
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case BLKIF_OP_WRITE_BARRIER:
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--
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2.1.0
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