[patch] staging: ft1000: add a range check in ft1000_ioctl()

[Dan Carpenter <dan.carpenter@oracle.com>]

msglen comes from get_user() so we need to check that it's not too
large.

The first element of "pioctl_dpram" is a short which holds the size of
the data the user wants.  I have chosen a limit which lets us fill the
rest of the struct.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
msglen is also apparently network endian?  My guess is that we should
just delete this code instead of trying to fix it.

diff --git a/drivers/staging/ft1000/ft1000-usb/ft1000_debug.c b/drivers/staging/ft1000/ft1000-usb/ft1000_debug.c
index 3251d2e..e0056c9 100644
--- a/drivers/staging/ft1000/ft1000-usb/ft1000_debug.c
+++ b/drivers/staging/ft1000/ft1000-usb/ft1000_debug.c
@@ -703,6 +703,8 @@ static long ft1000_ioctl (struct file *file, unsigned int command,
 			break;
 		msglen = htons(msglen);
                 //DEBUG("FT1000:ft1000_ioctl:msg length = %x\n", msglen);
+		if (msglen > sizeof(*pioctl_dpram) - sizeof(short))
+			msglen = sizeof(*pioctl_dpram) - sizeof(short);
                 if(copy_to_user (&pioctl_dpram->pseudohdr, pdpram_blk->pbuffer, msglen))
 				{
 					DEBUG("FT1000:ft1000_ioctl: copy fault occurred\n");