linux-kernel - Re: [PATCH 2/2] HID: core: only warn once of oversize hid report

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Date:   Mon, 22 Jul 2019 12:16:26 -0600
From:   Joshua Clayton <stillcompiling@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] HID: core: only warn once of oversize hid report

On Mon, Jul 22, 2019 at 11:23 AM Joe Perches <joe@...ches.com> wrote:
>
> On Mon, 2019-07-22 at 10:36 -0600, stillcompiling@...il.com wrote:
> > On HP spectre x360 convertible the message:
> > hid-sensor-hub 001F:8087:0AC2.0002: hid_field_extract() called with n (192) > 32! (kworker/1:2)
> > is continually printed many times per second, crowding out all other kernel logs
> > Protect dmesg by printing the warning only one time.
> []
> > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> []
> > @@ -1311,7 +1311,7 @@ u32 hid_field_extract(const struct hid_device *hid, u8 *report,
> >                       unsigned offset, unsigned n)
> >  {
> >       if (n > 32) {
> > -             hid_warn(hid, "hid_field_extract() called with n (%d) > 32! (%s)\n",
> > +             hid_warn_once(hid, "hid_field_extract() called with n (%d) > 32! (%s)\n",
> >                        n, current->comm);
> >               n = 32;
> >       }
>
> Is this papering over an actual defect somewhere else?

Sort of.
It doesn't correct the underlying issue, but I think this should go in
even along with the real fix.
The dmesg spamming has become a more serious problem for me than the
underlying issue.
Someone had a patch rejected that completely suppressed the message.

>From my limited understanding, the hid spec allows an unlimited size
for an hid report , but the kernel only allocated 32 bits, which was
more than anything used at that time. The 32 bit version is doing some
bit shifting and possibly endian correction with the 32 bit field, so
I was not comfortable just extending it to 192 or 256 bits without a
little more understanding.

> Trivially, this could use "%s: ...", __func__, ...
True. I can make that change.
>