linux-kernel - Re: [PATCH 06/12] i2c: rcar: set device parent and of

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAMRc=MctSufFn4Ku_8KBHmThvNOXo94DJDep-hzBem1yGw4wkg@mail.gmail.com>
Date: Tue, 6 Jan 2026 15:17:54 +0100
From: Bartosz Golaszewski <brgl@...nel.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>, 
	Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Mukesh Kumar Savaliya <mukesh.savaliya@....qualcomm.com>, 
	Viken Dadhaniya <viken.dadhaniya@....qualcomm.com>, Andi Shyti <andi.shyti@...nel.org>, 
	Florian Fainelli <florian.fainelli@...adcom.com>, Ray Jui <rjui@...adcom.com>, 
	Scott Branden <sbranden@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, Vignesh R <vigneshr@...com>, 
	Aaro Koskinen <aaro.koskinen@....fi>, Janusz Krzysztofik <jmkrzyszt@...il.com>, 
	Tony Lindgren <tony@...mide.com>, Andreas Kemnade <andreas@...nade.info>, 
	Kevin Hilman <khilman@...libre.com>, Roger Quadros <rogerq@...nel.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, 
	Patrice Chotard <patrice.chotard@...s.st.com>, Shawn Guo <shawnguo@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Fabio Estevam <festevam@...il.com>, Linus Walleij <linusw@...nel.org>, linux-i2c@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	linux-omap@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev, 
	linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH 06/12] i2c: rcar: set device parent and of_node through
 the adapter struct

On Tue, Jan 6, 2026 at 10:14 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Bartosz,
>
> On Tue, 23 Dec 2025 at 11:05, Bartosz Golaszewski
> <bartosz.golaszewski@....qualcomm.com> wrote:
> > Configure the parent device and the OF-node using dedicated fields in
> > struct i2c_adapter and avoid dereferencing the internal struct device.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>
>
> Thanks for your patch!
>
> > --- a/drivers/i2c/busses/i2c-rcar.c
> > +++ b/drivers/i2c/busses/i2c-rcar.c
> > @@ -1149,8 +1149,8 @@ static int rcar_i2c_probe(struct platform_device *pdev)
> >         adap->algo = &rcar_i2c_algo;
> >         adap->class = I2C_CLASS_DEPRECATED;
> >         adap->retries = 3;
> > -       adap->dev.parent = dev;
> > -       adap->dev.of_node = dev->of_node;
> > +       adap->parent = dev;
> > +       adap->of_node = dev->of_node;
> >         adap->bus_recovery_info = &rcar_i2c_bri;
> >         adap->quirks = &rcar_i2c_quirks;
> >         i2c_set_adapdata(adap, priv);
>
>     [....]
>     ret = rcar_i2c_clock_calculate(priv);
>     [...]
>     ret = i2c_add_numbered_adapter(adap);
>
> As rcar_i2c_clock_calculate() uses rcar_i2c_priv_to_dev(priv):
>
>     #define rcar_i2c_priv_to_dev(p)         ((p)->adap.dev.parent)
>
> I believe this will deference dev.parent before it is initialized by
> the newly added code in i2c_register_adapter().
>
> Let's check...
>
>     Unable to handle kernel NULL pointer dereference at virtual
> address 0000024c when read
>     [0000024c] *pgd=80000040004003, *pmd=00000000
>     Internal error: Oops: 206 [#1] SMP ARM
>     Modules linked in:
>     CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted
> 6.19.0-rc3-koelsch-04401-g9e22366a23cd #2288 NONE
>     Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>     PC is at device_property_read_u32_array+0x0/0x14
>     LR is at i2c_parse_timing+0x14/0x30
>     [...]
>     Call trace:
>      device_property_read_u32_array from i2c_parse_timing+0x14/0x30
>      i2c_parse_timing from i2c_parse_fw_timings+0x28/0x12c
>      i2c_parse_fw_timings from rcar_i2c_probe+0x1cc/0x534
>      rcar_i2c_probe from platform_probe+0x58/0x90
>

Thanks for the heads-up. I'm still waiting for Wolfram to decide if
these changes will be accepted or not before sending a v2.

Bartosz