Drivers: hv: vmbus: Fix synic per-cpu context initialization

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 748a1c4..332d7c3 100644 (file)
--- 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);