linux-kernel - Re: [PATCH v2] media: meson: vdec: Fix a NULL pointer dereference in amvdec_add

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Message-ID: <20211203133013.GJ9522@kadam>
Date:   Fri, 3 Dec 2021 16:30:13 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Zhou Qingyang <zhou1615@....edu>
Cc:     kjlu@....edu, Neil Armstrong <narmstrong@...libre.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Maxime Jourdan <mjourdan@...libre.com>,
        linux-media@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: meson: vdec: Fix a NULL pointer dereference in
 amvdec_add_ts()

On Fri, Dec 03, 2021 at 12:03:57AM +0800, Zhou Qingyang wrote:
> In amvdec_add_ts(), there is a dereference of kzalloc(), which could lead
> to a NULL pointer dereference on failure of kzalloc().
> 
> I fix this bug by adding a NULL check of new_ts.
> 
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
> Builds with CONFIG_VIDEO_MESON_VDEC=m show no new warnings,
> and our static analyzer no longer warns about this code.
> 
> Fixes: 876f123b8956 ("media: meson: vdec: bring up to compliance")
> Signed-off-by: Zhou Qingyang <zhou1615@....edu>
> ---
  ^^^
Thanks.  Next time put the meta commentary about how the bug was found
and the QC process under the the --- cut off line.  We don't need to
have that drama stored in the permanent git log.

Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>

regards,
dan carpenter