linux-kernel - [PATCH 3.2 16/18] KVM: VMX: fix use after free of vmx->loaded

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Message-ID: <lsq.1396827348.253620624@decadent.org.uk>
Date:	Mon, 07 Apr 2014 00:35:48 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Marcelo Tosatti" <mtosatti@...hat.com>,
	"Jan Kiszka" <jan.kiszka@...mens.com>
Subject: [PATCH 3.2 16/18] KVM: VMX: fix use after free of vmx->loaded_vmcs

3.2.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marcelo Tosatti <mtosatti@...hat.com>

commit 26a865f4aa8e66a6d94958de7656f7f1b03c6c56 upstream.

After free_loaded_vmcs executes, the "loaded_vmcs" structure
is kfreed, and now vmx->loaded_vmcs points to a kfreed area.
Subsequent free_loaded_vmcs then attempts to manipulate
vmx->loaded_vmcs.

Switch the order to avoid the problem.

https://bugzilla.redhat.com/show_bug.cgi?id=1047892

Reviewed-by: Jan Kiszka <jan.kiszka@...mens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kvm/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6273,8 +6273,8 @@ static void vmx_free_vcpu(struct kvm_vcp
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
 	free_vpid(vmx);
-	free_nested(vmx);
 	free_loaded_vmcs(vmx->loaded_vmcs);
+	free_nested(vmx);
 	kfree(vmx->guest_msrs);
 	kvm_vcpu_uninit(vcpu);
 	kmem_cache_free(kvm_vcpu_cache, vmx);

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