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

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Message-ID: <75f8dd3285046fa85e10b776c758b23b1f408a24.camel@mediatek.com>
Date:   Wed, 11 Aug 2021 08:18:02 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "ikjn@...omium.org" <ikjn@...omium.org>
CC:     "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
        Eddie Hung (洪正鑫) 
        <Eddie.Hung@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH 09/11] usb: xhci-mtk: check boundary before check tt

On Mon, 2021-08-09 at 15:32 +0800, Ikjoon Jang wrote:
> 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?
No, sch_ep->esit already ensure it, it's <= 64, see get_esit()

> 
> > 
> > +               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
> >