Re: [regression] Since kernel 6.3.1 logitech unify receiver not working properly

From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
To: Jiri Kosina <jikos@kernel.org>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
	"Linux regressions mailing list" <regressions@lists.linux.dev>,
	"Bagas Sanjaya" <bagasdotme@gmail.com>,
	"Filipe Laíns" <lains@riseup.net>,
	"Bastien Nocera" <hadess@hadess.net>,
	"open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	guy.b@bluewin.ch
Subject: Re: [regression] Since kernel 6.3.1 logitech unify receiver not working properly
Date: Thu, 25 May 2023 13:19:21 +0200	[thread overview]
Message-ID: <CAO-hwJJW1TDuZ2YXLf4pZhKO4UnM4ibUNsH=rpCyVjwNqixZtQ@mail.gmail.com> (raw)
In-Reply-To: <nycvar.YFH.7.76.2305251308471.29760@cbobk.fhfr.pm>

On Thu, May 25, 2023 at 1:10 PM Jiri Kosina <jikos@kernel.org> wrote:
>
> On Wed, 24 May 2023, Benjamin Tissoires wrote:
>
> > > > That bug is pre-existing (ie the problem was not introduced by that
> > > > commit), but who knows if the retry makes things worse (ie if it then
> > > > triggers on a retry, the response data will be the *previous* response).
> > > >
> > > > The whole "goto exit" games should be removed too, because we're in a
> > > > for-loop, and instead of "goto exit" it should just do "break".
> > > >
> > > > IOW, something like this might be worth testing.
> > > >
> > > > That said, while I think the code is buggy, I doubt this is the actual
> > > > cause of the problem people are reporting. But it would be lovely to
> > > > hear if the attached patch makes any difference, and I think this is
> > > > fixing a real - but unlikely - problem anyway.
> >
> > FWIW, Linus, your patch is
> > Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> >
> > Feel free to submit it to us or to apply it directly if you prefer as
> > this is clearly a fix for a code path issue.
>
> It would be nice to hear from the people who were able to reproduce the
> issue whether this makes any observable difference in behavior though. I
> don't currently think it would, as it fixes a potential NULL pointer
> dereference, which is not what has been reported.

Well, yes, I didn't mean it would fix the bug. But this is an obvious
fix that we need to take given that we now see it :)

>
> Has anyone of the affected people tried to bisect the issue?

I just checked the BZ linked above, and... it still doesn't work
(which is not surprising):
https://bugzilla.kernel.org/show_bug.cgi?id=217412#c33

Cheers,
Benjamin