KVM: x86: use array_index_nospec with indices that come from guest

commit c87bd4dd43a624109c3cc42d843138378a7f4548 upstream.

min and dest_id are guest-controlled indices. Using array_index_nospec()
after the bounds checks clamps these values to mitigate speculative execution
side-channels.

Signed-off-by: Thijs Raymakers <thijs@raymakers.nl>
Cc: stable@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fixes: 715062970f37 ("KVM: X86: Implement PV sched yield hypercall")
Fixes: bdf7ffc89922 ("KVM: LAPIC: Fix pv ipis out-of-bounds access")
Fixes: 4180bf1b655a ("KVM: X86: Implement "send IPI" hypercall")
Link: https://lore.kernel.org/r/20250804064405.4802-1-thijs@raymakers.nl
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 1a8148dec4afe9fbeb07f3aa7ea034c3dcee821d..33a6cb1ac6031e7e23d301e28b32300b8ecdf59c 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -860,6 +860,8 @@ static int __pv_send_ipi(unsigned long *ipi_bitmap, struct kvm_apic_map *map,
        if (min > map->max_apic_id)
                return 0;
 
+       min = array_index_nospec(min, map->max_apic_id + 1);
+
        for_each_set_bit(i, ipi_bitmap,
                min((u32)BITS_PER_LONG, (map->max_apic_id - min + 1))) {
                if (map->phys_map[min + i]) {

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dbd295ef3eba2e8520a7a35d13da0dedf00a90d7..17ec4c4a3d92e6662e860510c11fd8295764b236 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9969,8 +9969,11 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
        rcu_read_lock();
        map = rcu_dereference(vcpu->kvm->arch.apic_map);
 
-       if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id])
-               target = map->phys_map[dest_id]->vcpu;
+       if (likely(map) && dest_id <= map->max_apic_id) {
+               dest_id = array_index_nospec(dest_id, map->max_apic_id + 1);
+               if (map->phys_map[dest_id])
+                       target = map->phys_map[dest_id]->vcpu;
+       }
 
        rcu_read_unlock();