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Commit 87aeb54f authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Paolo Bonzini
Browse files

kvm: x86: use getboottime64 



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: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c45dcc71

arch/x86/kvm/x86.c

+5 −5
Original line number Diff line number Diff line
@@ -1165,7 +1165,7 @@ 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;
@@ -1188,13 +1188,13 @@ 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;