linux-kernel - [PATCH 3.10 107/139] KVM: x86: zero base3 of unusable segments

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Message-Id: <1509571624-5001-8-git-send-email-w@1wt.eu>
Date:   Wed,  1 Nov 2017 22:26:32 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 107/139] KVM: x86: zero base3 of unusable segments

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: Willy Tarreau <w@....eu>
---
 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 b70b67b..3d316ca 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4596,6 +4596,8 @@ 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;
 	}
 
-- 
2.8.0.rc2.1.gbe9624a