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Commit 3a33d030 authored by Tom Roeder's avatar Tom Roeder Committed by Paolo Bonzini
Browse files

kvm: x86/vmx: Use kzalloc for cached_vmcs12 

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: default avatar <syzbot+ded1696f6b50b615b630@syzkaller.appspotmail.com>
Fixes: 8fcc4b59
Cc: stable@vger.kernel.org
Signed-off-by: default avatarTom Roeder <tmroeder@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 85ba2b16

arch/x86/kvm/vmx/nested.c

+8 −4
Original line number Diff line number Diff line
@@ -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;

	}