linux-kernel - [PATCH 4/5] hv: don't reset hv_context.tsc

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Date:   Wed,  7 Dec 2016 01:16:27 -0800
From:   kys@...hange.microsoft.com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
        vkuznets@...hat.com, jasowang@...hat.com,
        leann.ogasawara@...onical.com
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>, <stable@...r.kernel.org>
Subject: [PATCH 4/5] hv: don't reset hv_context.tsc_page on crash

From: Vitaly Kuznetsov <vkuznets@...hat.com>

It may happen that secondary CPUs are still alive and resetting
hv_context.tsc_page will cause a consequent crash in read_hv_clock_tsc()
as we don't check for it being not NULL there. It is safe as we're not
freeing this page anyways.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Cc: <stable@...r.kernel.org>
---
 drivers/hv/hv.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index c11393c..60f14c4 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -309,9 +309,10 @@ void hv_cleanup(bool crash)
 
 		hypercall_msr.as_uint64 = 0;
 		wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
-		if (!crash)
+		if (!crash) {
 			vfree(hv_context.tsc_page);
-		hv_context.tsc_page = NULL;
+			hv_context.tsc_page = NULL;
+		}
 	}
 #endif
 }
-- 
1.7.4.1