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

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

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: Alan Cox <alan@redhat.com>

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.19-rc1-mm1/drivers/ide/ide-taskfile.c linux-2.6.19-rc1-mm1/drivers/ide/ide-taskfile.c
--- linux.vanilla-2.6.19-rc1-mm1/drivers/ide/ide-taskfile.c	2006-10-13 15:09:30.000000000 +0100
+++ linux-2.6.19-rc1-mm1/drivers/ide/ide-taskfile.c	2006-10-14 19:27:11.000000000 +0100
@@ -524,8 +524,8 @@
 	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 @@
 		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;