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 a40408895e23021fae472c0f9a05979b21e00563..fdbca15ecb449826c2c7511e304dc1a86f21730b 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -610,6 +610,8 @@ 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 b61f697479a37f78d854cf51b354cece8f313671..63df6c33e3a4709f443af885c22e37c4c81e78f9 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8359,8 +8359,11 @@ static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)
        rcu_read_lock();
        map = rcu_dereference(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();