media: lirc_zilog: Don't use dynamic static allocation

commit ac5b4b6 upstream.

Dynamic static allocation is evil, as Kernel stack is too low, and
ompilation complains about it on some archs:
	drivers/staging/media/lirc/lirc_zilog.c:967:1: warning: 'read' uses dynamic stack allocation [enabled by default]
Instead, let's enforce a limit for the buffer to be 64. That should
be more than enough.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/media/lirc/lirc_zilog.c

@@ -61,6 +61,9 @@
 #include <media/lirc_dev.h>
 #include <media/lirc.h>
 
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  64
+
 struct IR;
 
 struct IR_rx {
@@ -941,7 +944,14 @@ static ssize_t read(struct file *filep, char *outbuf, size_t n, loff_t *ppos)
 			schedule();
 			set_current_state(TASK_INTERRUPTIBLE);
 		} else {
-			unsigned char buf[rbuf->chunk_size];
+			unsigned char buf[MAX_XFER_SIZE];
+
+			if (rbuf->chunk_size > sizeof(buf)) {
+				zilog_error("chunk_size is too big (%d)!\n",
+					    rbuf->chunk_size);
+				ret = -EINVAL;
+				break;
+			}
 			m = lirc_buffer_read(rbuf, buf);
 			if (m == rbuf->chunk_size) {
 				ret = copy_to_user((void *)outbuf+written, buf,