Re: [PATCH v2] HID: core: demote warning to debug level

[Benjamin Tissoires <bentiss@kernel.org>]

On Aug 24 2026, Matteo Croce wrote:
> Il giorno lun 24 ago 2026 alle ore 12:25 Lee Jones <lee@kernel.org> ha scritto:
> >
> > On Wed, 10 Jun 2026, Jiri Kosina wrote:
> >
> > > On Sat, 23 May 2026, Matteo Croce wrote:
> > >
> > > > From: Matteo Croce <teknoraver@meta.com>
> > > >
> > > > The log level for short  messages was changed from debug to warning,
> > > > flooding syslog on systems with devices that regularly send
> > > > short reports, in my case an UPS:
> > > >
> > > >     $ dmesg |grep -c 'Event data for report .* was too short'
> > > >     35
> > > >
> > > > Demote it back to debug level.
> > > >
> > > > Fixes: 0a3fe972a7cb ("HID: core: Mitigate potential OOB by removing bogus memset()")
> > > > Signed-off-by: Matteo Croce <teknoraver@meta.com>
> > >
> > > Applied, thanks.
> >
> > FWIW, I'd like to contest this patch.
> >
> > The warning is real.  It means that the HID report was rejected and as
> > such something on the system will be now be non-functional.  Silencing
> > the warning is not helpful.  It does not fix the issue, and now the user
> > / admin has no idea that its even happening.
> >
> > This warning has caught a bunch of genuine issues related to testing
> > infrastructure and incorrectly coded firmware that have subsequently
> > been rectified.
> >
> > Please don't hide this issue.  Fix the root cause instead.
> >
> > --
> > Lee Jones
> 
> Hi,
> 
> the message was debug long before and was promoted to warning during a refactor.
> With my patch I just restored the previous priority.
> 

Sorry, but no. The new kernel code restored the old behavior: if the
incoming buffer is long enough but the incoming report has a shorter
size, we still have the dbg_hid() call, so it's transparent for users.

The hid_warns are now only emitted when there is an obvious error with
the report *that the kernel can not fix*.

So having this patch would do exactly what Lee said: this would prevent
users to understand why their device doesn't work.

This patch "fixed" a temporary wrong attempt at solving an OOB, the old
behavior is restored, we should not even have this type of arguments.

Cheers,
Benjamin