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kvm: x86/vmx: Use kzalloc for cached_vmcs12

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This changes the allocation of cached_vmcs12 to use kzalloc instead of
kmalloc. This removes the information leak found by Syzkaller (see
Reported-by) in this case and prevents similar leaks from happening
based on cached_vmcs12.

It also changes vmx_get_nested_state to copy out the full 4k VMCS12_SIZE
in copy_to_user rather than only the size of the struct.

Tested: rebuilt against head, booted, and ran the syszkaller repro
  https://syzkaller.appspot.com/text?tag=ReproC&x=174efca3400000 without
  observing any problems.

Reported-by: syzbot+ded1696f6b50b615b630@syzkaller.appspotmail.com
Fixes: 8fcc4b5923af5de58b80b53a069453b135693304
Cc: stable@vger.kernel.org
Signed-off-by: Tom Roeder <tmroeder@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Tom Roeder 2019-01-24 13:48:20 -08:00 committed by Paolo Bonzini
parent 85ba2b165d
commit 3a33d030da
1 changed files with 8 additions and 4 deletions
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12
arch/x86/kvm/vmx/nested.c
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@ -4140,11 +4140,11 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)
if (r < 0)
goto out_vmcs02;
vmx->nested.cached_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL);
vmx->nested.cached_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL);
if (!vmx->nested.cached_vmcs12)
goto out_cached_vmcs12;
vmx->nested.cached_shadow_vmcs12 = kmalloc(VMCS12_SIZE, GFP_KERNEL);
vmx->nested.cached_shadow_vmcs12 = kzalloc(VMCS12_SIZE, GFP_KERNEL);
if (!vmx->nested.cached_shadow_vmcs12)
goto out_cached_shadow_vmcs12;
@ -5263,13 +5263,17 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
copy_shadow_to_vmcs12(vmx);
}
if (copy_to_user(user_kvm_nested_state->data, vmcs12, sizeof(*vmcs12)))
/*
* Copy over the full allocated size of vmcs12 rather than just the size
* of the struct.
*/
if (copy_to_user(user_kvm_nested_state->data, vmcs12, VMCS12_SIZE))
return -EFAULT;
if (nested_cpu_has_shadow_vmcs(vmcs12) &&
vmcs12->vmcs_link_pointer != -1ull) {
if (copy_to_user(user_kvm_nested_state->data + VMCS12_SIZE,
get_shadow_vmcs12(vcpu), sizeof(*vmcs12)))
get_shadow_vmcs12(vcpu), VMCS12_SIZE))
return -EFAULT;
}