[patch 155/164] KVM: Fix wallclock version writing race
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From: Greg KH on 1 Jul 2010 17:00 2.6.33-stable review patch. If anyone has any objections, please let me know. ------------------ From: Avi Kivity <avi(a)redhat.com> 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(a)redhat.com> Signed-off-by: Avi Kivity <avi(a)redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de> (cherry picked from commit 9ed3c444ab8987c7b219173a2f7807e3f71e234e) --- arch/x86/kvm/x86.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -641,14 +641,22 @@ static int do_set_msr(struct kvm_vcpu *v 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)); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |