linux-kernel - Re: [PATCH] drm: check for NULL parameter in exported drm_get_format_name() function.

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Message-ID: <20161122173157.GD31595@intel.com>
Date:   Tue, 22 Nov 2016 19:31:57 +0200
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Liviu Dudau <Liviu.Dudau@....com>,
        Jani Nikula <jani.nikula@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Eric Engestrom <eric@...estrom.ch>,
        LKML <linux-kernel@...r.kernel.org>,
        DRI devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm: check for NULL parameter in exported
 drm_get_format_name() function.

On Tue, Nov 22, 2016 at 12:23:59PM -0500, Rob Clark wrote:
> On Tue, Nov 22, 2016 at 11:50 AM, Ville Syrjälä
> <ville.syrjala@...ux.intel.com> wrote:
> > On Tue, Nov 22, 2016 at 04:41:06PM +0000, Liviu Dudau wrote:
> >> drm_get_format_name() de-references the buf parameter without checking
> >> if the pointer was not NULL. Given that the function is EXPORT-ed, lets
> >> sanitise the parameters before proceeding.
> >>
> >> Fixes: b3c11ac267d461d3d5 ("drm: move allocation out of drm_get_format_name())
> >> Cc: Eric Engestrom <eric@...estrom.ch>
> >> Cc: Rob Clark <robdclark@...il.com>
> >> Cc: Jani Nikula <jani.nikula@...el.com>
> >> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> >>
> >> Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> >> ---
> >>  drivers/gpu/drm/drm_fourcc.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> >> index 90d2cc8..0a3ff0b 100644
> >> --- a/drivers/gpu/drm/drm_fourcc.c
> >> +++ b/drivers/gpu/drm/drm_fourcc.c
> >> @@ -85,6 +85,9 @@ EXPORT_SYMBOL(drm_mode_legacy_fb_format);
> >>   */
> >>  const char *drm_get_format_name(uint32_t format, struct drm_format_name_buf *buf)
> >>  {
> >> +     if (!buf)
> >> +             return NULL;
> >> +
> >
> > Seems rather pointless to me. Why would you ever pass NULL to this guy?
> 
> perhaps BUG_ON(!buf)...

And how does that differ from just buf->foo?

> 
> BR,
> -R
> 
> >>       snprintf(buf->str, sizeof(buf->str),
> >>                "%c%c%c%c %s-endian (0x%08x)",
> >>                printable_char(format & 0xff),
> >> --
> >> 2.10.2
> >>
> >> _______________________________________________
> >> dri-devel mailing list
> >> dri-devel@...ts.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> > --
> > Ville Syrjälä
> > Intel OTC
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel OTC

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