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From: Tyler Hicks <tyhicks@canonical.com>
To: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Gen Zhang <blackgod016574@gmail.com>,
	sean@poorly.run, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm_edid-load: Fix a missing-check bug in drivers/gpu/drm/drm_edid_load.c
Date: Tue, 18 Jun 2019 17:38:49 -0500	[thread overview]
Message-ID: <20190618223848.GD6248@lindsey> (raw)
In-Reply-To: <87o93u7d3s.fsf@intel.com>

On 2019-05-22 17:55:35, Jani Nikula wrote:
> On Wed, 22 May 2019, Gen Zhang <blackgod016574@gmail.com> wrote:
> > In drm_load_edid_firmware(), fwstr is allocated by kstrdup(). And fwstr
> > is dereferenced in the following codes. However, memory allocation 
> > functions such as kstrdup() may fail and returns NULL. Dereferencing 
> > this null pointer may cause the kernel go wrong. Thus we should check 
> > this kstrdup() operation.
> > Further, if kstrdup() returns NULL, we should return ERR_PTR(-ENOMEM) to
> > the caller site.
> 
> strsep() handles the NULL pointer just fine, so there won't be a NULL
> dereference. However this patch seems like the right thing to do anyway.

I came across this thread while triaging CVE-2019-12382. I agree that
the code before was fine but more complex than necessary. There's no
real security impact here since a NULL pointer dereference was not
possible. I've requested that MITRE reject CVE-2019-12382.

This change is a nice improvement, though.

Tyler

> 
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
> 
> >
> > Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> >
> > ---
> > diff --git a/drivers/gpu/drm/drm_edid_load.c b/drivers/gpu/drm/drm_edid_load.c
> > index a491509..a0e107a 100644
> > --- a/drivers/gpu/drm/drm_edid_load.c
> > +++ b/drivers/gpu/drm/drm_edid_load.c
> > @@ -290,6 +290,8 @@ struct edid *drm_load_edid_firmware(struct drm_connector *connector)
> >  	 * the last one found one as a fallback.
> >  	 */
> >  	fwstr = kstrdup(edid_firmware, GFP_KERNEL);
> > +	if (!fwstr)
> > +		return ERR_PTR(-ENOMEM);
> >  	edidstr = fwstr;
> >  
> >  	while ((edidname = strsep(&edidstr, ","))) {
> > ---
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center

      parent reply	other threads:[~2019-06-18 22:38 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-22 12:39 Gen Zhang
2019-05-22 14:55 ` Jani Nikula
2019-05-24  2:32   ` [PATCH] drm_edid-load: Fix a missing-check bug in drm_load_edid_firmware() Gen Zhang
2019-05-24 18:02     ` Jani Nikula
2019-06-18 22:38   ` Tyler Hicks [this message]

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