On 17/06/2016 17:48, Arnd Bergmann wrote:
> 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;
>
>
Queued, thanks.
Paolo
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