Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1375988

[PATCH 3.12 09/98] xen-blkback: only read request operation from shared ring once

Show all headers | View raw

From: Roger Pau Monné <roger.pau@citrix.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 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 8d8807563d99..ab225ff1af8e 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -388,8 +388,8 @@ 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:
@@ -436,8 +436,8 @@ 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:
-- 
2.8.1

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH 3.12 00/98] 3.12.58-stable review Jiri Slaby <jslaby@suse.cz> - 2016-04-11 15:30 +0200
  Re: [PATCH 3.12 00/98] 3.12.58-stable review Guenter Roeck <linux@roeck-us.net> - 2016-04-11 15:40 +0200
    Re: [PATCH 3.12 00/98] 3.12.58-stable review Jiri Slaby <jslaby@suse.cz> - 2016-04-14 10:30 +0200
  [PATCH 3.12 01/98] ipr: Fix out-of-bounds null overwrite Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 18/98] ALSA: rawmidi: Make snd_rawmidi_transmit() race-free Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 23/98] KVM: SVM: add rdmsr support for AMD event registers Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 08/98] xen-netback: use RING_COPY_REQUEST() throughout Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 07/98] xen-netback: don't use last request to determine minimum Tx credit Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 03/98] ipv4: Don't do expensive useless work during inetdev destroy. Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 27/98] perf, nmi: Fix unknown NMI warning Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 14/98] sched: Fix race between task_group and sched_task_group Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 20/98] memcg: do not hang on OOM when killed by userspace OOM access to memory reserves Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 19/98] ALSA: seq: Fix leak of pool buffer at concurrent writes Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 09/98] xen-blkback: only read request operation from shared ring once Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 05/98] kernel: Provide READ_ONCE and ASSIGN_ONCE Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
      Re: [PATCH 3.12 05/98] kernel: Provide READ_ONCE and ASSIGN_ONCE Christian Borntraeger <borntraeger@de.ibm.com> - 2016-04-11 16:20 +0200
    [PATCH 3.12 06/98] xen: Add RING_COPY_REQUEST() Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 17/98] drivers/base/memory.c: fix kernel warning during memory hotplug on ppc64 Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 04/98] umount: Do not allow unmounting rootfs. Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 10/98] xen-blkback: read from indirect descriptors only once Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 02/98] ipr: Fix regression when loading firmware Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 15/98] Btrfs: skip locking when searching commit root Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
  Re: [PATCH 3.12 00/98] 3.12.58-stable review shuahkh <shuahkh@osg.sisa.samsung.com> - 2016-04-11 19:30 +0200

csiph-web