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| author | Roger Pau Monné <roger.pau@citrix.com> | 2015-11-03 16:34:09 +0000 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2016-01-25 10:43:43 +0000 |
| commit | 8a4577e63e31c1296fd8ee4016345f0be8284c47 (patch) | |
| tree | 4b2ad2f1f8974b1629f6059f2947c4bc09ac00fd /drivers/block | |
| parent | 2419fe7ea0b854800512474153a41d1938ec0cfa (diff) | |
| download | linux-stable-8a4577e63e31c1296fd8ee4016345f0be8284c47.tar.gz linux-stable-8a4577e63e31c1296fd8ee4016345f0be8284c47.tar.bz2 linux-stable-8a4577e63e31c1296fd8ee4016345f0be8284c47.zip | |
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>
[ luis: backported to 3.16:
- replaced READ_ONCE() by ACCESS_ONCE() ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Diffstat (limited to 'drivers/block')
| -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 f65b807e3236..ef64f59921a7 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -391,8 +391,8 @@ 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 = ACCESS_ONCE(src->operation); + switch (dst->operation) { case BLKIF_OP_READ: case BLKIF_OP_WRITE: case BLKIF_OP_WRITE_BARRIER: @@ -439,8 +439,8 @@ 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 = ACCESS_ONCE(src->operation); + switch (dst->operation) { case BLKIF_OP_READ: case BLKIF_OP_WRITE: case BLKIF_OP_WRITE_BARRIER: |