On 05/04/2010 03:02 PM, Avi Kivity wrote:
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.
Signed-off-by: Avi Kivity<avi@xxxxxxxxxx>
This was pointed out by Naphtali.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f6f8dad..c3152d7 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));
--
error compiling committee.c: too many arguments to function
--
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