Input: joydev - prevent potential read overflow in ioctl

The problem here is that "len" might be less than "joydev->nabs" so the
loops which verfy abspam[i] and keypam[] might read beyond the buffer.

Fixes: 999b874 ("Input: joydev - validate axis/button maps before clobbering current ones")
Signed-off-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/r/YCyzR8WvFRw4HWw6@mwanda
[dtor: additional check for len being even in joydev_handle_JSIOCSBTNMAP]
Cc: [email protected]
Signed-off-by: Dmitry Torokhov <[email protected]>

drivers/input/joydev.c

@@ -456,7 +456,7 @@ static int joydev_handle_JSIOCSAXMAP(struct joydev *joydev,
 	if (IS_ERR(abspam))
 		return PTR_ERR(abspam);
 
-	for (i = 0; i < joydev->nabs; i++) {
+	for (i = 0; i < len && i < joydev->nabs; i++) {
 		if (abspam[i] > ABS_MAX) {
 			retval = -EINVAL;
 			goto out;
@@ -480,14 +480,17 @@ static int joydev_handle_JSIOCSBTNMAP(struct joydev *joydev,
 	int i;
 	int retval = 0;
 
+	if (len % sizeof(*keypam))
+		return -EINVAL;
+
 	len = min(len, sizeof(joydev->keypam));
 
 	/* Validate the map. */
 	keypam = memdup_user(argp, len);
 	if (IS_ERR(keypam))
 		return PTR_ERR(keypam);
 
-	for (i = 0; i < joydev->nkey; i++) {
+	for (i = 0; i < (len / 2) && i < joydev->nkey; i++) {
 		if (keypam[i] > KEY_MAX || keypam[i] < BTN_MISC) {
 			retval = -EINVAL;
 			goto out;