linux-kernel - [PATCH 3.16 071/233] KVM: x86: zero base3 of unusable segments

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Date:   Sat, 09 Sep 2017 22:47:14 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Paolo Bonzini" <pbonzini@...hat.com>,
        "David Hildenbrand" <david@...hat.com>,
        "Dan Carpenter" <dan.carpenter@...cle.com>,
        "Radim Krčmář" <rkrcmar@...hat.com>
Subject: [PATCH 3.16 071/233] KVM: x86: zero base3 of unusable segments

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

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

From: Radim Krčmář <rkrcmar@...hat.com>

commit f0367ee1d64d27fa08be2407df5c125442e885e3 upstream.

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@...cle.com>
Fixes: 1aa366163b8b ("KVM: x86 emulator: consolidate segment accessors")
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kvm/x86.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4749,6 +4749,8 @@ static bool emulator_get_segment(struct
 
 	if (var.unusable) {
 		memset(desc, 0, sizeof(*desc));
+		if (base3)
+			*base3 = 0;
 		return false;
 	}