From: Joe Perches <joe@perches.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Arnd Bergmann <arnd@kernel.org>, Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <s.hauer@pengutronix.de>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>,
NXP Linux Team <linux-imx@nxp.com>,
Marco Felsch <m.felsch@pengutronix.de>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Liu Ying <victor.liu@nxp.com>,
dri-devel <dri-devel@lists.freedesktop.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC patch] vsprintf: Allow %pe to print non PTR_ERR %pe uses as decimal
Date: Wed, 24 Mar 2021 12:24:10 -0700 [thread overview]
Message-ID: <d184069de43135a9c9e5f031447faf98ab3f437d.camel@perches.com> (raw)
In-Reply-To: <9feab1e8-4dee-6b79-03f7-7b9f0cb24f6e@rasmusvillemoes.dk>
On Wed, 2021-03-24 at 18:33 +0100, Rasmus Villemoes wrote:
> On 24/03/2021 18.20, Joe Perches wrote:
> > On Wed, 2021-03-24 at 09:52 -0700, Joe Perches wrote:
> > > On Wed, 2021-03-24 at 17:42 +0100, Arnd Bergmann wrote:
> > > > On Wed, Mar 24, 2021 at 3:20 PM Joe Perches <joe@perches.com> wrote:
> > > []
> > > > > > diff --git a/drivers/gpu/drm/imx/imx-ldb.c b/drivers/gpu/drm/imx/imx-ldb.c
> > > > > []
> > > > > > @@ -197,6 +197,12 @@ static void imx_ldb_encoder_enable(struct drm_encoder *encoder)
> > > > > > int dual = ldb->ldb_ctrl & LDB_SPLIT_MODE_EN;
> > > > > > int mux = drm_of_encoder_active_port_id(imx_ldb_ch->child, encoder);
> > > > > >
> > > > > > + if (mux < 0 || mux >= ARRAY_SIZE(ldb->clk_sel)) {
> > > > > > + dev_warn(ldb->dev, "%s: invalid mux %d\n",
> > > > > > + __func__, ERR_PTR(mux));
> > > > >
> > > > > This does not compile without warnings.
> > > > >
> > > > > drivers/gpu/drm/imx/imx-ldb.c: In function ‘imx_ldb_encoder_enable’:
> > > > > drivers/gpu/drm/imx/imx-ldb.c:201:22: warning: format ‘%d’ expects argument of type ‘int’, but argument 4 has type ‘void *’ [-Wformat=]
> > > > > 201 | dev_warn(ldb->dev, "%s: invalid mux %d\n",
> > > > > | ^~~~~~~~~~~~~~~~~~~~~~
> > > > >
> > > > > If you want to use ERR_PTR, the %d should be %pe as ERR_PTR
> > > > > is converting an int a void * to decode the error type and
> > > > > emit it as a string.
> > > >
> > > > Sorry about that.
> > > >
> > > > I decided against using ERR_PTR() in order to also check for
> > > > positive array overflow, but the version I tested was different from
> > > > the version I sent.
> > > >
> > > > v3 coming.
> > >
> > > Thanks. No worries.
> > >
> > > Up to you, vsprintf would emit the positive mux as a funky hashed
> > > hex value by default if you use ERR_PTR with mux > ARRAY_SIZE so
> > > perhaps %d without the ERR_PTR use makes the most sense.
> > >
>
> >
> > Maybe it's better to output non PTR_ERR %pe uses as decimal so this
> > sort of code would work.
>
> No, because that would leak the pointer value when somebody has
> accidentally passed a real kernel pointer to %pe.
I think it's not really an issue.
_All_ code that uses %p<foo> extensions need inspection anyway.
It's already possible to intentionally 'leak' the ptr value
by using %pe, -ptr so I think that's not really an issue.
>
> If the code wants a cute -EFOO string explaining what's wrong, what
> about "%pe", ERR_PTR(mux < 0 : mux : -ERANGE)? Or two separate error
> messages
>
> if (mux < 0)
> ...
> else if (mux >= ARRAY_SIZE())
> ...
Multiple tests, more unnecessary code, multiple format strings, etc...
next prev parent reply other threads:[~2021-03-24 19:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 12:17 [PATCH] [v2] drm/imx: imx-ldb: fix out of bounds array access warning Arnd Bergmann
2021-03-24 14:20 ` Joe Perches
2021-03-24 16:42 ` Arnd Bergmann
2021-03-24 16:52 ` Joe Perches
2021-03-24 17:20 ` [RFC patch] vsprintf: Allow %pe to print non PTR_ERR %pe uses as decimal Joe Perches
2021-03-24 17:33 ` Rasmus Villemoes
2021-03-24 19:24 ` Joe Perches [this message]
2021-03-24 21:27 ` Rasmus Villemoes
2021-03-24 22:18 ` Joe Perches
2021-03-24 22:36 ` Rasmus Villemoes
2021-03-24 22:46 ` Joe Perches
2021-03-24 16:14 ` [PATCH] [v2] drm/imx: imx-ldb: fix out of bounds array access warning kernel test robot
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