diff options
| author | Roger Pau Monné <roger.pau@citrix.com> | 2015-11-03 16:34:09 +0000 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-04-11 10:57:43 +0200 |
| commit | 89940b048407baa69cc6c822a8d6468dd6ce0a0d (patch) | |
| tree | f634f0fc81a3278b3937dd9b7bc7c7984a969d95 | |
| parent | 0e31faaf02f5245278898f54d9ac07582967e321 (diff) | |
xen-blkback: only read request operation from shared ring once
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 <roger.pau@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "Jan Beulich" <JBeulich@suse.com>
[wt: s/READ_ONCE/ACCESS_ONCE for 3.10]
Signed-off-by: Willy Tarreau <w@1wt.eu>
| -rw-r--r-- | drivers/block/xen-blkback/common.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 60103e251..467cb48fc 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 = ACCESS_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 = ACCESS_ONCE(src->operation); + switch (dst->operation) { case BLKIF_OP_READ: case BLKIF_OP_WRITE: case BLKIF_OP_WRITE_BARRIER: |