patch "USB: devio: Don't corrupt user memory" added to usb-linus

This is a note to let you know that I've just added the patch titled

USB: devio: Don't corrupt user memory

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Dan Carpenter <[email protected]>
Date: Fri, 22 Sep 2017 23:43:46 +0300
Subject: USB: devio: Don't corrupt user memory

The user buffer has "uurb->buffer_length" bytes. If the kernel has more information than that, we should truncate it instead of writing past the end of the user's buffer. I added a WARN_ONCE() to help the user debug the issue.

---
 drivers/usb/core/devio.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

index e9326f31db8d..4664e543cf2f 100644
@@ -1576,7 +1576,11 @@ static int proc_do_submiturb(struct usb_dev_state *ps, struct usbdevfs_urb *uurb
 			totlen += isopkt[u].length;
 		}
 		u *= sizeof(struct usb_iso_packet_descriptor);
-		uurb->buffer_length = totlen;
+		if (totlen <= uurb->buffer_length)
+			uurb->buffer_length = totlen;
+		else
+			WARN_ONCE(1, "uurb->buffer_length is too short %d vs %d",
+				  totlen, uurb->buffer_length);
 		break;
 
 	default:

2.14.1