cciss: fix info leak in cciss_ioctl32_passthru()

The arg64 struct has a hole after ->buf_size which isn't cleared.  Or if
any of the calls to copy_from_user() fail then that would cause an
information leak as well.

This was assigned CVE-2013-2147.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/cciss.c

@@ -1189,6 +1189,7 @@ static int cciss_ioctl32_passthru(struct block_device *bdev, fmode_t mode,
 	int err;
 	u32 cp;
 
+	memset(&arg64, 0, sizeof(arg64));
 	err = 0;
 	err |=
 	    copy_from_user(&arg64.LUN_info, &arg32->LUN_info,