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authorAvi Kivity <avi@redhat.com>2010-05-04 15:00:37 +0300
committerAvi Kivity <avi@redhat.com>2010-05-19 11:36:36 +0300
commit9ed3c444ab8987c7b219173a2f7807e3f71e234e (patch)
tree4214bfb01447b73768ae1e8175b04fccb2b3495f /arch
parent8facbbff071ff2b19268d3732e31badc60471e21 (diff)
downloadop-kernel-dev-9ed3c444ab8987c7b219173a2f7807e3f71e234e.zip
op-kernel-dev-9ed3c444ab8987c7b219173a2f7807e3f71e234e.tar.gz
KVM: Fix wallclock version writing race
Wallclock writing uses an unprotected global variable to hold the version; this can cause one guest to interfere with another if both write their wallclock at the same time. Acked-by: Glauber Costa <glommer@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dff08e5..54f73b6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -754,14 +754,22 @@ static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
{
- static int version;
+ int version;
+ int r;
struct pvclock_wall_clock wc;
struct timespec boot;
if (!wall_clock)
return;
- version++;
+ r = kvm_read_guest(kvm, wall_clock, &version, sizeof(version));
+ if (r)
+ return;
+
+ if (version & 1)
+ ++version; /* first time write, random junk */
+
+ ++version;
kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
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