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kvm: x86: svm: Fix NULL pointer dereference when AVIC not enabled 

Launching VM w/ AVIC disabled together with pass-through device
results in NULL pointer dereference bug with the following call trace.

    RIP: 0010:svm_refresh_apicv_exec_ctrl+0x17e/0x1a0 [kvm_amd]

    Call Trace:
     kvm_vcpu_update_apicv+0x44/0x60 [kvm]
     kvm_arch_vcpu_ioctl_run+0x3f4/0x1c80 [kvm]
     kvm_vcpu_ioctl+0x3d8/0x650 [kvm]
     do_vfs_ioctl+0xaa/0x660
     ? tomoyo_file_ioctl+0x19/0x20
     ksys_ioctl+0x67/0x90
     __x64_sys_ioctl+0x1a/0x20
     do_syscall_64+0x57/0x190
     entry_SYSCALL_64_after_hwframe+0x44/0xa9

Investigation shows that this is due to the uninitialized usage of
struct vapu_svm.ir_list in the svm_set_pi_irte_mode(), which is
called from svm_refresh_apicv_exec_ctrl().

The ir_list is initialized only if AVIC is enabled. So, fixes by
adding a check if AVIC is enabled in the svm_refresh_apicv_exec_ctrl().

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=206579
Fixes: 8937d76239 ("kvm: x86: svm: Add support to (de)activate posted interrupts.")
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Suravee Suthikulpanit 2020-02-21 08:52:17 -06:00 committed by Paolo Bonzini
parent 624e18f92f
commit 93fd9666c2
1 changed files with 3 additions and 0 deletions
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3
arch/x86/kvm/svm.c
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@ -5232,6 +5232,9 @@ static void svm_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
struct vmcb *vmcb = svm->vmcb;
bool activated = kvm_vcpu_apicv_active(vcpu);
if (!avic)
return;
if (activated) {
/**
* During AVIC temporary deactivation, guest could update