KVM: x86: Fully initialize 'struct kvm_lapic_irq' in kvm_pv_kick_cpu_op()

'vector' and 'trig_mode' fields of 'struct kvm_lapic_irq' are left
uninitialized in kvm_pv_kick_cpu_op(). While these fields are normally
not needed for APIC_DM_REMRD, they're still referenced by
__apic_accept_irq() for trace_kvm_apic_accept_irq(). Fully initialize
the structure to avoid consuming random stack memory.

Fixes: a183b638b61c ("KVM: x86: make apic_accept_irq tracepoint more generic")
Reported-by: syzbot+d6caa905917d353f0d07@syzkaller.appspotmail.com
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220708125147.593975-1-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0c3e85e8fce93a4a05a112564ac122e8ab51daf5..143e37298d8a41f7c8616cb2b7d77188d96dbd1e 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9143,15 +9143,17 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
  */
 static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid)
 {
-       struct kvm_lapic_irq lapic_irq;
-
-       lapic_irq.shorthand = APIC_DEST_NOSHORT;
-       lapic_irq.dest_mode = APIC_DEST_PHYSICAL;
-       lapic_irq.level = 0;
-       lapic_irq.dest_id = apicid;
-       lapic_irq.msi_redir_hint = false;
+       /*
+        * All other fields are unused for APIC_DM_REMRD, but may be consumed by
+        * common code, e.g. for tracing. Defer initialization to the compiler.
+        */
+       struct kvm_lapic_irq lapic_irq = {
+               .delivery_mode = APIC_DM_REMRD,
+               .dest_mode = APIC_DEST_PHYSICAL,
+               .shorthand = APIC_DEST_NOSHORT,
+               .dest_id = apicid,
+       };
 
-       lapic_irq.delivery_mode = APIC_DM_REMRD;
        kvm_irq_delivery_to_apic(kvm, NULL, &lapic_irq, NULL);
 }