KVM reads the current boottime value as a struct timespec in order to
calculate the guest wallclock time, resulting in an overflow in 2038
on 32-bit systems.
The data then gets passed as an unsigned 32-bit number to the guest,
and that in turn overflows in 2106.
We cannot do much about the second overflow, which affects both 32-bit
and 64-bit hosts, but we can ensure that they both behave the same
way and don't overflow until 2106, by using getboottime64() to read
a timespec64 value.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
arch/x86/kvm/x86.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 53241618e3c9..f79c86510408 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1163,7 +1163,7 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
int version;
int r;
struct pvclock_wall_clock wc;
- struct timespec boot;
+ struct timespec64 boot;
if (!wall_clock)
return;
@@ -1186,13 +1186,13 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
* wall clock specified here. guest system time equals host
* system time for us, thus we must fill in host boot time here.
*/
- getboottime(&boot);
+ getboottime64(&boot);
if (kvm->arch.kvmclock_offset) {
- struct timespec ts = ns_to_timespec(kvm->arch.kvmclock_offset);
- boot = timespec_sub(boot, ts);
+ struct timespec64 ts = ns_to_timespec64(kvm->arch.kvmclock_offset);
+ boot = timespec64_sub(boot, ts);
}
- wc.sec = boot.tv_sec;
+ wc.sec = (u32)boot.tv_sec; /* overflow in 2106 guest time */
wc.nsec = boot.tv_nsec;
wc.version = version;
--
2.9.0
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