On Tue, 7 Jun 2016, Michał Pecio wrote:
> Since ed_schedule begins with marking the ED as "operational",
> the ED may be left in such state even if scheduling actually
> fails.
>
> This allows future submission attempts to smuggle this ED to the
> hardware behind the scheduler's back and without linking it to
> the ohci->eds_in_use list.
>
> The former causes bandwidth saturation and data loss on isoc
> endpoints, the latter crashes the kernel when attempt is made
> to unlink such ED from this list.
>
> Fix ed_schedule to update ED state only on successful return.
>
> Signed-off-by: Michal Pecio <michal.pecio@xxxxxxxxx>
> ---
> drivers/usb/host/ohci-q.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c
> index d029bbe..641fed6 100644
> --- a/drivers/usb/host/ohci-q.c
> +++ b/drivers/usb/host/ohci-q.c
> @@ -183,7 +183,6 @@ static int ed_schedule (struct ohci_hcd *ohci, struct ed *ed)
> {
> int branch;
>
> - ed->state = ED_OPER;
> ed->ed_prev = NULL;
> ed->ed_next = NULL;
> ed->hwNextED = 0;
> @@ -259,6 +258,8 @@ static int ed_schedule (struct ohci_hcd *ohci, struct ed *ed)
> /* the HC may not see the schedule updates yet, but if it does
> * then they'll be properly ordered.
> */
> +
> + ed->state = ED_OPER;
> return 0;
> }
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Greg, in principle this should go to -stable. However, it looks like
this might break some applications that currently sort-of work, even
though they shouldn't. Therefore we have decided not to mark this
patch for -stable at present.
Alan Stern
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