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Subject[PATCH 5/5] Drivers: hv: vmbus: Fix synic per-cpu context initialization
Date
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
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