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[PATCH 2/4] KVM: x86: zero base3 of unusable segments

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  [PATCH 2/4] KVM: x86: zero base3 of unusable segments Radim Krčmář <rkrcmar@redhat.com> - 2017-05-18 19:40 +0200
    Re: [PATCH 2/4] KVM: x86: zero base3 of unusable segments David Hildenbrand <david@redhat.com> - 2017-05-19 15:40 +0200

#1644783 — [PATCH 2/4] KVM: x86: zero base3 of unusable segments

Static checker noticed that base3 could be used uninitialized if the
segment was not present (useable).  Random stack values probably would
not pass VMCS entry checks.

Reported-by:  Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 1aa366163b8b ("KVM: x86 emulator: consolidate segment accessors")
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 arch/x86/kvm/x86.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b54125b590e8..eed8272dd52e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5053,6 +5053,8 @@ static bool emulator_get_segment(struct x86_emulate_ctxt *ctxt, u16 *selector,
 
 	if (var.unusable) {
 		memset(desc, 0, sizeof(*desc));
+		if (base3)
+			*base3 = 0;
 		return false;
 	}
 
-- 
2.13.0

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#1645606

On 18.05.2017 19:37, Radim Krčmář wrote:
> Static checker noticed that base3 could be used uninitialized if the
> segment was not present (useable).  Random stack values probably would
> not pass VMCS entry checks.
> 
> Reported-by:  Dan Carpenter <dan.carpenter@oracle.com>
> Fixes: 1aa366163b8b ("KVM: x86 emulator: consolidate segment accessors")
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
>  arch/x86/kvm/x86.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b54125b590e8..eed8272dd52e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5053,6 +5053,8 @@ static bool emulator_get_segment(struct x86_emulate_ctxt *ctxt, u16 *selector,
>  
>  	if (var.unusable) {
>  		memset(desc, 0, sizeof(*desc));
> +		if (base3)
> +			*base3 = 0;
>  		return false;
>  	}
>  
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 

Thanks,

David

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