Bluetooth: RFCOMM - Fix info leak in ioctl(RFCOMMGETDEVLIST)

The RFCOMM code fails to initialize the two padding bytes of struct
rfcomm_dev_list_req inserted for alignment before copying it to
userland. Additionally there are two padding bytes in each instance of
struct rfcomm_dev_info. The ioctl() that for disclosures two bytes plus
dev_num times two bytes uninitialized kernel heap memory.

Allocate the memory using kzalloc() to fix this issue.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bluetooth/rfcomm/tty.c

@@ -456,7 +456,7 @@ static int rfcomm_get_dev_list(void __user *arg)
 
 	size = sizeof(*dl) + dev_num * sizeof(*di);
 
-	dl = kmalloc(size, GFP_KERNEL);
+	dl = kzalloc(size, GFP_KERNEL);
 	if (!dl)
 		return -ENOMEM;