Re: [PATCH 1/2] drm/imx: Fix error handling for a kmemdup() call in imx_pd_bind()

From: Julia Lawall <julia.lawall@lip6.fr>
To: Navid Emamdoost <navid.emamdoost@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Rob Herring <robh@kernel.org>,
	kernel-janitors@vger.kernel.org,
	Peter Senna Tschudin <peter.senna@collabora.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	David Airlie <airlied@linux.ie>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>, Kangjie Lu <kjlu@umn.edu>,
	LKML <linux-kernel@vger.kernel.org>,
	dri-devel@lists.freedesktop.org,
	Navid Emamdoost <emamd001@umn.edu>,
	Markus Elfring <Markus.Elfring@web.de>,
	NXP Linux Team <linux-imx@nxp.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Stephen McCamant <smccaman@umn.edu>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/2] drm/imx: Fix error handling for a kmemdup() call in imx_pd_bind()
Date: Sat, 12 Oct 2019 21:24:19 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1910122122370.3049@hadrien> (raw)
In-Reply-To: <CAEkB2ERCGJ6abNXfPNX7nbwkwD7qYTPYjYsNGzZwynn5CbPCzg@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 2017 bytes --]

On Sat, 12 Oct 2019, Navid Emamdoost wrote:

> On Sat, Oct 12, 2019 at 4:07 AM Markus Elfring <Markus.Elfring@web.de> wrote:
> >
> > From: Markus Elfring <elfring@users.sourceforge.net>
> > Date: Sat, 12 Oct 2019 10:30:21 +0200
> >
> > The return value from a call of the function “kmemdup” was not checked
> > in this function implementation. Thus add the corresponding error handling.
> >
> > Fixes: 19022aaae677dfa171a719e9d1ff04823ce65a65 ("staging: drm/imx: Add parallel display support")
> > Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> > ---
> >  drivers/gpu/drm/imx/parallel-display.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/imx/parallel-display.c b/drivers/gpu/drm/imx/parallel-display.c
> > index 35518e5de356..39c4798f56b6 100644
> > --- a/drivers/gpu/drm/imx/parallel-display.c
> > +++ b/drivers/gpu/drm/imx/parallel-display.c
> > @@ -210,8 +210,13 @@ static int imx_pd_bind(struct device *dev, struct device *master, void *data)
> >                 return -ENOMEM;
> >
> >         edidp = of_get_property(np, "edid", &imxpd->edid_len);
> > -       if (edidp)
> > +       if (edidp) {
> >                 imxpd->edid = kmemdup(edidp, imxpd->edid_len, GFP_KERNEL);
> > +               if (!imxpd->edid) {
> > +                       devm_kfree(dev, imxpd);
>
> You should not try to free imxpd here as it is a resource-managed
> allocation via devm_kzalloc(). It means memory allocated with this
> function is
>  automatically freed on driver detach. So, this patch introduces a double-free.

No, it's not double freed since the proposed code frees it with a devm
function, removing it from the list of things to free later.  One can
wonder why the free has to be made apparent, though.

julia

>
> > +                       return -ENOMEM;
> > +               }
> > +       }
> >
> >         ret = of_property_read_string(np, "interface-pix-fmt", &fmt);
> >         if (!ret) {
> > --
> > 2.23.0
> >
>
>
> --
> Navid.
>

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel