Drivers: hv: vmbus: Close timing hole that can corrupt per-cpu page
authorMichael Kelley <mikelley@microsoft.com>
Thu, 18 May 2017 17:46:07 +0000 (10:46 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 25 May 2017 13:42:42 +0000 (15:42 +0200)
Extend the disabling of preemption to include the hypercall so that
another thread can't get the CPU and corrupt the per-cpu page used
for hypercall arguments.

Cc: <Stable@vger.kernel.org> #4.11
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/hv/hv.c

index 61fc8ce..2ea1220 100644 (file)
@@ -82,10 +82,15 @@ int hv_post_message(union hv_connection_id connection_id,
        aligned_msg->message_type = message_type;
        aligned_msg->payload_size = payload_size;
        memcpy((void *)aligned_msg->payload, payload, payload_size);
-       put_cpu_ptr(hv_cpu);
 
        status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);
 
+       /* Preemption must remain disabled until after the hypercall
+        * so some other thread can't get scheduled onto this cpu and
+        * corrupt the per-cpu post_msg_page
+        */
+       put_cpu_ptr(hv_cpu);
+
        return status & 0xFFFF;
 }