From: Roger Pau Monné <[email protected]> commit 1f13d75ccb806260079e0679d55d9253e370ec8a upstream.
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. Signed-off-by: Roger Pau Monné <[email protected]> Signed-off-by: David Vrabel <[email protected]> Signed-off-by: Konrad Rzeszutek Wilk <[email protected]> Cc: "Jan Beulich" <[email protected]> Signed-off-by: Willy Tarreau <[email protected]> --- 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 60103e2..6774cba 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -269,8 +269,8 @@ 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; - 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: @@ -305,8 +305,8 @@ 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; - 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: -- 2.8.0.rc2.1.gbe9624a
