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From:   kys@linuxonhyperv.com
To:     gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com,
        jasowang@redhat.com, sthemmin@microsoft.com,
        Michael.H.Kelley@microsoft.com, vkuznets@redhat.com
Cc:     Michael Kelley <mikelley@microsoft.com>,
        "K . Y . Srinivasan" <kys@microsoft.com>
Subject: [PATCH 5/5] Drivers: hv: vmbus: Fix synic per-cpu context initialization
Date:   Fri, 10 Aug 2018 23:06:11 +0000
Message-Id: <20180810230611.2114-5-kys@linuxonhyperv.com>
In-Reply-To: <20180810230611.2114-1-kys@linuxonhyperv.com>
References: <20180810230520.2055-1-kys@linuxonhyperv.com>
 <20180810230611.2114-1-kys@linuxonhyperv.com>
Reply-To: kys@microsoft.com
Sender: linux-kernel-owner@vger.kernel.org
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From: Michael Kelley <mikelley@microsoft.com>

If hv_synic_alloc() errors out, the state of the per-cpu context
for some CPUs is unknown since the zero'ing is done as each
CPU is iterated over.  In such case, hv_synic_cleanup() may try to
free memory based on uninitialized values.  Fix this by zero'ing
the per-cpu context for all CPUs before doing any memory
allocations that might fail.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 748a1c4172a6..332d7c34be5c 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -189,6 +189,17 @@ static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
 int hv_synic_alloc(void)
 {
 	int cpu;
+	struct hv_per_cpu_context *hv_cpu;
+
+	/*
+	 * First, zero all per-cpu memory areas so hv_synic_free() can
+	 * detect what memory has been allocated and cleanup properly
+	 * after any failures.
+	 */
+	for_each_present_cpu(cpu) {
+		hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
+		memset(hv_cpu, 0, sizeof(*hv_cpu));
+	}
 
 	hv_context.hv_numa_map = kcalloc(nr_node_ids, sizeof(struct cpumask),
 					 GFP_KERNEL);
@@ -198,10 +209,8 @@ int hv_synic_alloc(void)
 	}
 
 	for_each_present_cpu(cpu) {
-		struct hv_per_cpu_context *hv_cpu
-			= per_cpu_ptr(hv_context.cpu_context, cpu);
+		hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
 
-		memset(hv_cpu, 0, sizeof(*hv_cpu));
 		tasklet_init(&hv_cpu->msg_dpc,
 			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
 
-- 
2.18.0