Re: [Qemu-devel] [PATCH] usb: ohci: limit the number of link eds

[Li Qiang]

Hello Gerd,

Ping...

2017-02-07 18:23 GMT+08:00 Li Qiang <address@hidden>:

> From: Li Qiang <address@hidden>
>
> The guest may builds an infinite loop with link eds. This patch
> limit the number of linked ed to avoid this.
>
> Signed-off-by: Li Qiang <address@hidden>
> ---
>  hw/usb/hcd-ohci.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
> index c82a92f..4a63f3b 100644
> --- a/hw/usb/hcd-ohci.c
> +++ b/hw/usb/hcd-ohci.c
> @@ -42,6 +42,8 @@
>
>  #define OHCI_MAX_PORTS 15
>
> +#define ED_LINK_LIMIT 4
> +
>  static int64_t usb_frame_time;
>  static int64_t usb_bit_time;
>
> @@ -1184,7 +1186,7 @@ static int ohci_service_ed_list(OHCIState *ohci,
> uint32_t head, int completion)
>      uint32_t next_ed;
>      uint32_t cur;
>      int active;
> -
> +    uint32_t link_cnt = 0;
>      active = 0;
>
>      if (head == 0)
> @@ -1199,6 +1201,11 @@ static int ohci_service_ed_list(OHCIState *ohci,
> uint32_t head, int completion)
>
>          next_ed = ed.next & OHCI_DPTR_MASK;
>
> +        if (++link_cnt > ED_LINK_LIMIT) {
> +            ohci_die(ohci);
> +            return 0;
> +        }
> +
>          if ((ed.head & OHCI_ED_H) || (ed.flags & OHCI_ED_K)) {
>              uint32_t addr;
>              /* Cancel pending packets for ED that have been paused.  */
> --
> 1.8.3.1
>
>