[media] rc: ir-lirc-codec: fix potential integer overflow

'n' may be bigger than MAX_INT*sizeof(int), if so checking of truncated
(int)(n/sizeof(int)) for LIRCBUF_SIZE overflow and then using nontruncated 'count'
doesn't make sense.  Also n may be up to sizeof(int)-1 bytes bigger than expected,
so check value of (n % sizeof(int)) too.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/rc/ir-lirc-codec.c

@@ -100,7 +100,8 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char *buf,
 	struct lirc_codec *lirc;
 	struct rc_dev *dev;
 	int *txbuf; /* buffer with values to transmit */
-	int ret = 0, count;
+	int ret = 0;
+	size_t count;
 
 	lirc = lirc_get_pdata(file);
 	if (!lirc)
@@ -110,7 +111,7 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char *buf,
 		return -EINVAL;
 
 	count = n / sizeof(int);
-	if (count > LIRCBUF_SIZE || count % 2 == 0)
+	if (count > LIRCBUF_SIZE || count % 2 == 0 || n % sizeof(int) != 0)
 		return -EINVAL;
 
 	txbuf = memdup_user(buf, n);