[PATCH] ide: add sanity checking to ide taskfile ioctl

Without this the user can feed in bogus values and get very bogus
results. Security impact is minimal as this ioctl isn't available to
unpriviledged processes anyway.

Reported to the l/k list and found with an auditing tool.
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/ide/ide-taskfile.c

@@ -524,8 +524,8 @@ int ide_taskfile_ioctl (ide_drive_t *drive, unsigned int cmd, unsigned long arg)
 	task_ioreg_t *hobsptr	= args.hobRegister;
 	int err			= 0;
 	int tasksize		= sizeof(struct ide_task_request_s);
-	int taskin		= 0;
-	int taskout		= 0;
+	unsigned int taskin	= 0;
+	unsigned int taskout	= 0;
 	u8 io_32bit		= drive->io_32bit;
 	char __user *buf = (char __user *)arg;
 
@@ -538,8 +538,13 @@ int ide_taskfile_ioctl (ide_drive_t *drive, unsigned int cmd, unsigned long arg)
 		return -EFAULT;
 	}
 
-	taskout = (int) req_task->out_size;
-	taskin  = (int) req_task->in_size;
+	taskout = req_task->out_size;
+	taskin  = req_task->in_size;
+	
+	if (taskin > 65536 || taskout > 65536) {
+		err = -EINVAL;
+		goto abort;
+	}
 
 	if (taskout) {
 		int outtotal = tasksize;