linux-kernel - Re: [PATCH] HID: i2c-hid: ensure various commands do not interfere with each other

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Message-ID: <nycvar.YFH.7.76.2409112019460.31206@cbobk.fhfr.pm>
Date: Wed, 11 Sep 2024 20:20:55 +0200 (CEST)
From: Jiri Kosina <jikos@...nel.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
cc: ". Benjamin Tissoires" <bentiss@...nel.org>, 
    Douglas Anderson <dianders@...omium.org>, 
    Hans de Goede <hdegoede@...hat.com>, Kenny Levinsen <kl@...wtf>, 
    linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: i2c-hid: ensure various commands do not interfere
 with each other

On Wed, 11 Sep 2024, Dmitry Torokhov wrote:

> > > i2c-hid uses 2 shared buffers: command and "raw" input buffer for
> > > sending requests to peripherals and read data from peripherals when
> > > executing variety of commands. Such commands include reading of HID
> > > registers, requesting particular power mode, getting and setting
> > > reports and so on. Because all such requests use the same 2 buffers
> > > they should not execute simultaneously.
> > > 
> > > Fix this by introducing "cmd_lock" mutex and acquire it whenever
> > > we needs to access ihid->cmdbuf or idid->rawbuf.
> > > 
> > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > 
> > Thanks for the fix, Dmitry. Out of curiosity, did you find it by code 
> > inspection, or have you actually seen it happening for real, making the 
> > driver misbehave?
> 
> No, I have not observed this issue in the wild, that is why I di dnot
> tag it explicitly for stable. 

Thanks. I was asking whether I should rush it in still for 6.11, or 
whether waiting for 6.12 merge window is sufficient.

So I will send it to Linus for 6.12, but I still think tagging for stable 
should probably be done.

> It came about when I was reviewing Goodix HID SPI driver, noticed that 
> it was using a shared buffer, asked to and locking, and realized that 
> I2C HID needed the same. And just got around to sending out the fix...
> 
> As far as I can see USB HID driver does not need it - it does not share
> URBs but rather allocates new one for each request (via
> usb_control_msg()).

Indeed, USB HID is fine in that respect.

Thanks a lot,

-- 
Jiri Kosina
SUSE Labs