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SubjectRe: 2.6.33 bugs (USBFS, Intel graphic)
On Fri, 26 Feb 2010, Greg KH wrote:

> Hm, so it's back to the original idea of just doing a kzalloc of the
> initial buffer, that should solve the problem that Marcus found.
>
> I'll go dig that back up and if you could test it, that would be most
> appreciated.

Here's a better solution. In theory we could copy just the individual
packets from within the transfer buffer, but that would probably take
longer than simply copying the whole buffer.

(This was a little hasty; I haven't even compile-tested the patch.
Some small fixes may be needed.)

Alan Stern


-----------------------------------------------------------------------

This patch fixes a bug in the way isochronous input data is returned
to userspace for usbfs transfers. The entire buffer must be copied,
not just the first actual_length bytes, because the individual packets
will be discontiguous if any of them are short.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: stable <stable@kernel.org>

---

Index: usb-2.6/drivers/usb/core/devio.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/devio.c
+++ usb-2.6/drivers/usb/core/devio.c
@@ -1176,6 +1176,13 @@ static int proc_do_submiturb(struct dev_
free_async(as);
return -ENOMEM;
}
+ /* Isochronous input data may end up being discontiguous
+ * if some of the packets are short. Clear the buffer so
+ * that the gaps don't leak kernel data to userspace.
+ */
+ if (is_in && uurb->type == USBDEVFS_URB_TYPE_ISO)
+ memset(as->urb->transfer_buffer, 0,
+ uurb->buffer_length);
}
as->urb->dev = ps->dev;
as->urb->pipe = (uurb->type << 30) |
@@ -1312,10 +1319,14 @@ static int processcompl(struct async *as
void __user *addr = as->userurb;
unsigned int i;

- if (as->userbuffer && urb->actual_length)
- if (copy_to_user(as->userbuffer, urb->transfer_buffer,
- urb->actual_length))
+ if (as->userbuffer && urb->actual_length) {
+ if (urb->number_of_packets > 0) /* Isochronous */
+ i = urb->transfer_buffer_length;
+ else /* Non-Isoc */
+ i = urb->actual_length;
+ if (copy_to_user(as->userbuffer, urb->transfer_buffer, i))
goto err_out;
+ }
if (put_user(as->status, &userurb->status))
goto err_out;
if (put_user(urb->actual_length, &userurb->actual_length))


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