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

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

[gregkh]

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 fa1ed74eb1c233be6131ec92df21ab46499a15b6 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
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.

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/core/devio.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index e9326f31db8d..4664e543cf2f 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -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