exec.c, compat.c: fix count(), compat_count() bounds checking

With MAX_ARG_STRINGS set to 0x7FFFFFFF, and being passed to 'count()' and
compat_count(), it would appear that the current max bounds check of
fs/exec.c:394:

	if(++i > max)
		return -E2BIG;

would never trigger. Since 'i' is of type int, so values would wrap and the
function would continue looping.

Simple fix seems to be chaning ++i to i++ and checking for '>='.

Signed-off-by: Jason Baron <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: "Ollie Wild" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/compat.c

@@ -1239,7 +1239,7 @@ static int compat_count(compat_uptr_t __user *argv, int max)
 			if (!p)
 				break;
 			argv++;
-			if(++i > max)
+			if (i++ >= max)
 				return -E2BIG;
 		}
 	}

fs/exec.c

@@ -391,7 +391,7 @@ static int count(char __user * __user * argv, int max)
 			if (!p)
 				break;
 			argv++;
-			if(++i > max)
+			if (i++ >= max)
 				return -E2BIG;
 			cond_resched();
 		}