Re: [PATCH] HID: Increase maximum report size allowed by hid_field_extract()

[Kai-Heng Feng]

at 17:42, Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> wrote:

> Hi,
>
>
> On Fri, Mar 8, 2019 at 6:11 AM Kai-Heng Feng
> <kai.heng.feng@xxxxxxxxxxxxx> wrote:
> > Commit 71f6fa90a353 ("HID: increase maximum global item tag report size
> > to 256") increases the max report size from 128 to 256.
> >
> > We also need to update the report size in hid_field_extract() otherwise
> > it complains and truncates now valid report size:
> > [ 406.165461] hid-sensor-hub 001F:8086:22D8.0002: hid_field_extract()  
> > called with n (192) > 32! (kworker/5:1)
> >
> > BugLink: https://bugs.launchpad.net/bugs/1818547
> > Fixes: 71f6fa90a353 ("HID: increase maximum global item tag report size  
> > to 256")
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > ---
> >  drivers/hid/hid-core.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> > index 9993b692598f..860e21ec6a49 100644
> > --- a/drivers/hid/hid-core.c
> > +++ b/drivers/hid/hid-core.c
> > @@ -1301,10 +1301,10 @@ static u32 __extract(u8 *report, unsigned  
> > offset, int n)
> >  u32 hid_field_extract(const struct hid_device *hid, u8 *report,
> >                         unsigned offset, unsigned n)
>
> Ronald (Cc-ed) raised quite a good point:
> what's the benefit of removing the error message if this function (and
> __extract) can only report an unsigned 32 bits value?

I didnât spot this, sorry.

> My take is we should revert 94a9992f7dbdfb28976b upstream and think at
> a better solution.

I think using a new fix to replace it will be a better approach, as it at  
least partially solves the issue.

Kai-Heng

> Cheers,
> Benjamin
>
> > {
> > -       if (n > 32) {
> > -               hid_warn(hid, "hid_field_extract() called with n (%d) >  
> > 32! (%s)\n",
> > +       if (n > 256) {
> > +               hid_warn(hid, "hid_field_extract() called with n (%d) >  
> > 256! (%s)\n",
> >                          n, current->comm);
> > -               n = 32;
> > +               n = 256;
> >         }
> >
> >         return __extract(report, offset, n);
> > â

> > 2.17.1