[PATCH] hvc_console: prevent wrapping in hvc_console_print()

[Roel Kluin <roel.kluin@gmail.com>]

This was found by code analysis, is it needed?
------------------------------>8-------------8<---------------------------------
If we subtract too much on unsigned i it wraps.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index 94e7e3c..d06313c 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -161,10 +161,10 @@ static void hvc_console_print(struct console *co, const char *b,
 			}
 		} else {
 			r = cons_ops[index]->put_chars(vtermnos[index], c, i);
-			if (r <= 0) {
+			if (r <= 0 || r > i) {
 				/* throw away chars on error */
 				i = 0;
-			} else if (r > 0) {
+			} else {
 				i -= r;
 				if (i > 0)
 					memmove(c, c+r, i);