linux-kernel - [PATCH 4.14 096/101] arm64: KVM: Avoid setting the upper 32 bits of VTCR

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Date:   Mon,  7 Jan 2019 13:33:24 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 4.14 096/101] arm64: KVM: Avoid setting the upper 32 bits of VTCR_EL2 to 1

4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Will Deacon <will.deacon@....com>

commit df655b75c43fba0f2621680ab261083297fd6d16 upstream.

Although bit 31 of VTCR_EL2 is RES1, we inadvertently end up setting all
of the upper 32 bits to 1 as well because we define VTCR_EL2_RES1 as
signed, which is sign-extended when assigning to kvm->arch.vtcr.

Lucky for us, the architecture currently treats these upper bits as RES0
so, whilst we've been naughty, we haven't set fire to anything yet.

Cc: <stable@...r.kernel.org>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Christoffer Dall <christoffer.dall@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/include/asm/kvm_arm.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -99,7 +99,7 @@
 			 TCR_EL2_ORGN0_MASK | TCR_EL2_IRGN0_MASK | TCR_EL2_T0SZ_MASK)
 
 /* VTCR_EL2 Registers bits */
-#define VTCR_EL2_RES1		(1 << 31)
+#define VTCR_EL2_RES1		(1U << 31)
 #define VTCR_EL2_HD		(1 << 22)
 #define VTCR_EL2_HA		(1 << 21)
 #define VTCR_EL2_PS_MASK	TCR_EL2_PS_MASK