diff options
| author | Avi Kivity <avi@redhat.com> | 2010-05-04 15:00:37 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-07-05 11:16:14 -0700 |
| commit | 12bf0ef607767d6817f20557d246b1eb6c11eb99 (patch) | |
| tree | be5939f8d28656652cd9c720a913c37d13049d38 | |
| parent | 01b2090b73c8364b457d4c8d0961db2d1635726a (diff) | |
| download | lwn-12bf0ef607767d6817f20557d246b1eb6c11eb99.tar.gz lwn-12bf0ef607767d6817f20557d246b1eb6c11eb99.zip | |
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
(cherry picked from commit 9ed3c444ab8987c7b219173a2f7807e3f71e234e)
| -rw-r--r-- | arch/x86/kvm/x86.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 31f4d2a4fc53..efa690ffa02e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -641,14 +641,22 @@ 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)); |