1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/char/hvc_vio.c b/drivers/char/hvc_vio.c
index f5212eb2b41d..9add81ceb440 100644
--- a/drivers/char/hvc_vio.c
+++ b/drivers/char/hvc_vio.c
@@ -31,10 +31,13 @@
 
 #include <linux/types.h>
 #include <linux/init.h>
+
 #include <asm/hvconsole.h>
 #include <asm/vio.h>
 #include <asm/prom.h>
 
+#include "hvc_console.h"
+
 char hvc_driver_name[] = "hvc_console";
 
 static struct vio_device_id hvc_driver_table[] __devinitdata = {
@@ -48,6 +51,14 @@ static int filtered_get_chars(uint32_t vtermno, char *buf, int count)
         unsigned long got;
         int i;
 
+        /*
+         * Vio firmware will read up to SIZE_VIO_GET_CHARS at its own discretion
+         * so we play safe and avoid the situation where got > count which could
+         * overload the flip buffer.
+         */
+        if (count < SIZE_VIO_GET_CHARS)
+                return -EAGAIN;
+
         got = hvc_get_chars(vtermno, buf, count);
 
         /*