linux-kernel - [PATCH 3.16 034/254] arm: KVM: Fix VTTBR_BADDR_MASK BUG

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Message-ID: <lsq.1519831218.738136564@decadent.org.uk>
Date:   Wed, 28 Feb 2018 15:20:18 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Christoffer Dall" <christoffer.dall@...aro.org>,
        "Kristina Martsenko" <kristina.martsenko@....com>,
        "Marc Zyngier" <marc.zyngier@....com>
Subject: [PATCH 3.16 034/254] arm: KVM: Fix VTTBR_BADDR_MASK BUG_ON off-by-one

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

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

From: Marc Zyngier <marc.zyngier@....com>

commit 5553b142be11e794ebc0805950b2e8313f93d718 upstream.

VTTBR_BADDR_MASK is used to sanity check the size and alignment of the
VTTBR address. It seems to currently be off by one, thereby only
allowing up to 39-bit addresses (instead of 40-bit) and also
insufficiently checking the alignment. This patch fixes it.

This patch is the 32bit pendent of Kristina's arm64 fix, and
she deserves the actual kudos for pinpointing that one.

Fixes: f7ed45be3ba52 ("KVM: ARM: World-switch implementation")
Reported-by: Kristina Martsenko <kristina.martsenko@....com>
Reviewed-by: Christoffer Dall <christoffer.dall@...aro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/include/asm/kvm_arm.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/arch/arm/include/asm/kvm_arm.h
+++ b/arch/arm/include/asm/kvm_arm.h
@@ -161,8 +161,7 @@
 #else
 #define VTTBR_X		(5 - KVM_T0SZ)
 #endif
-#define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
-#define VTTBR_BADDR_MASK  (((1LLU << (40 - VTTBR_X)) - 1) << VTTBR_BADDR_SHIFT)
+#define VTTBR_BADDR_MASK  (((1LLU << (40 - VTTBR_X)) - 1) << VTTBR_X)
 #define VTTBR_VMID_SHIFT  (48LLU)
 #define VTTBR_VMID_MASK	  (0xffLLU << VTTBR_VMID_SHIFT)