linux-kernel - Re: [PATCH 09/11] usb: xhci-mtk: check boundary before check tt

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Date:   Mon, 9 Aug 2021 15:32:31 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-usb@...r.kernel.org,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Eddie Hung <eddie.hung@...iatek.com>
Subject: Re: [PATCH 09/11] usb: xhci-mtk: check boundary before check tt

Hi Chunfeng,

On Fri, Jul 30, 2021 at 4:50 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
>
> check_sch_tt() will access fs_bus_bw[] array, check boundary
> firstly to avoid out-of-bounds issue.
>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> ---
>  drivers/usb/host/xhci-mtk-sch.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-mtk-sch.c b/drivers/usb/host/xhci-mtk-sch.c
> index 10c0f0f6461f..c2f13d69c607 100644
> --- a/drivers/usb/host/xhci-mtk-sch.c
> +++ b/drivers/usb/host/xhci-mtk-sch.c
> @@ -600,13 +600,14 @@ static int check_sch_bw(struct mu3h_sch_bw_info *sch_bw,
>          * and find a microframe where its worst bandwidth is minimum.
>          */
>         for (offset = 0; offset < sch_ep->esit; offset++) {
> -               ret = check_sch_tt(sch_ep, offset);
> -               if (ret)
> -                       continue;
>
>                 if ((offset + sch_ep->num_budget_microframes) > esit_boundary)
>                         break;

Instead of dropping it,
I'm wondering if it should be checked against (offset & 63) == 0 when it's 64?

>
> +               ret = check_sch_tt(sch_ep, offset);
> +               if (ret)
> +                       continue;
> +
>                 worst_bw = get_max_bw(sch_bw, sch_ep, offset);
>                 if (worst_bw > bw_boundary)
>                         continue;
> --
> 2.18.0
>