linux-kernel - [PATCH v4 1/7] x86/hyper-v: check for required priviliges in hyperv

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Message-Id: <20180124132337.30138-2-vkuznets@redhat.com>
Date:   Wed, 24 Jan 2018 14:23:31 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, x86@...nel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        Andy Lutomirski <luto@...nel.org>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Cathy Avery <cavery@...hat.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        linux-kernel@...r.kernel.org, devel@...uxdriverproject.org
Subject: [PATCH v4 1/7] x86/hyper-v: check for required priviliges in hyperv_init()

In hyperv_init() we presume we always have access to VP index and hypercall
MSRs while according to the specification we should check if we're allowed
to access the corresponding MSRs before accessing them.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/hyperv/hv_init.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 189a398290db..21f9d53d9f00 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -110,12 +110,19 @@ static int hv_cpu_init(unsigned int cpu)
  */
 void hyperv_init(void)
 {
-	u64 guest_id;
+	u64 guest_id, required_msrs;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;
 
+	/* Absolutely required MSRs */
+	required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
+		HV_X64_MSR_VP_INDEX_AVAILABLE;
+
+	if ((ms_hyperv.features & required_msrs) != required_msrs)
+		return;
+
 	/* Allocate percpu VP index */
 	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
 				    GFP_KERNEL);
-- 
2.14.3