diff options
| author | Avi Kivity | 2010-05-04 15:00:37 +0300 |
|---|---|---|
| committer | Avi Kivity | 2010-05-19 11:36:36 +0300 |
| commit | 9ed3c444ab8987c7b219173a2f7807e3f71e234e (patch) | |
| tree | 4214bfb01447b73768ae1e8175b04fccb2b3495f /arch/x86 | |
| parent | 8facbbff071ff2b19268d3732e31badc60471e21 (diff) | |
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/x86')
| -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 dff08e527ec7..54f73b6a006b 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)); |