linux-kernel - Re: [PATCH v3] media: meson: vdec: potential dereference of null pointer

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Message-ID: <9790448d-53bb-cc61-655e-dda70ae97fa3@baylibre.com>
Date:   Thu, 13 Jan 2022 09:56:08 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>, hverkuil-cisco@...all.nl,
        mchehab@...nel.org, gregkh@...uxfoundation.org,
        khilman@...libre.com, jbrunet@...libre.com,
        martin.blumenstingl@...glemail.com, p.zabel@...gutronix.de
Cc:     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 v3] media: meson: vdec: potential dereference of null
 pointer

On 13/01/2022 07:59, Jiasheng Jiang wrote:
> As the possible failure of the kzalloc(), the 'new_ts' could be NULL
> pointer.
> Therefore, it should be better to check it in order to avoid the
> dereference of the NULL pointer.
> Also, the caller esparser_queue() needs to deal with the return value of
> the amvdec_add_ts().
> 
> Fixes: 876f123b8956 ("media: meson: vdec: bring up to compliance")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog
> 
> v1 -> v2
> 
> * Change 1. Change the return type of amvdec_add_ts from void to int.
> * Change 2. Return -ENOMEN if alloc fail and return 0 if not.
> * Change 3. Modify the caller to deal with the error.
> 
> v2 -> v3
> 
> * Change 1. Fix the indentation and refine the commit message.
> ---
>  drivers/staging/media/meson/vdec/esparser.c     | 7 ++++++-
>  drivers/staging/media/meson/vdec/vdec_helpers.c | 8 ++++++--
>  drivers/staging/media/meson/vdec/vdec_helpers.h | 4 ++--
>  3 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/media/meson/vdec/esparser.c b/drivers/staging/media/meson/vdec/esparser.c
> index db7022707ff8..86ccc8937afc 100644
> --- a/drivers/staging/media/meson/vdec/esparser.c
> +++ b/drivers/staging/media/meson/vdec/esparser.c
> @@ -328,7 +328,12 @@ esparser_queue(struct amvdec_session *sess, struct vb2_v4l2_buffer *vbuf)
>  
>  	offset = esparser_get_offset(sess);
>  
> -	amvdec_add_ts(sess, vb->timestamp, vbuf->timecode, offset, vbuf->flags);
> +	ret = amvdec_add_ts(sess, vb->timestamp, vbuf->timecode, offset, vbuf->flags);
> +	if (ret) {
> +		v4l2_m2m_buf_done(vbuf, VB2_BUF_STATE_ERROR);
> +		return ret;
> +	}
> +
>  	dev_dbg(core->dev, "esparser: ts = %llu pld_size = %u offset = %08X flags = %08X\n",
>  		vb->timestamp, payload_size, offset, vbuf->flags);
>  
> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> index 203d7afa085d..7d2a75653250 100644
> --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> @@ -227,13 +227,16 @@ int amvdec_set_canvases(struct amvdec_session *sess,
>  }
>  EXPORT_SYMBOL_GPL(amvdec_set_canvases);
>  
> -void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
> -		   struct v4l2_timecode tc, u32 offset, u32 vbuf_flags)
> +int amvdec_add_ts(struct amvdec_session *sess, u64 ts,
> +		  struct v4l2_timecode tc, u32 offset, u32 vbuf_flags)
>  {
>  	struct amvdec_timestamp *new_ts;
>  	unsigned long flags;
>  
>  	new_ts = kzalloc(sizeof(*new_ts), GFP_KERNEL);
> +	if (!new_ts)
> +		return -ENOMEM;
> +
>  	new_ts->ts = ts;
>  	new_ts->tc = tc;
>  	new_ts->offset = offset;
> @@ -242,6 +245,7 @@ void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
>  	spin_lock_irqsave(&sess->ts_spinlock, flags);
>  	list_add_tail(&new_ts->list, &sess->timestamps);
>  	spin_unlock_irqrestore(&sess->ts_spinlock, flags);
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(amvdec_add_ts);
>  
> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.h b/drivers/staging/media/meson/vdec/vdec_helpers.h
> index 88137d15aa3a..4bf3e61d081b 100644
> --- a/drivers/staging/media/meson/vdec/vdec_helpers.h
> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.h
> @@ -56,8 +56,8 @@ void amvdec_dst_buf_done_offset(struct amvdec_session *sess,
>   * @offset: offset in the VIFIFO where the associated packet was written
>   * @flags: the vb2_v4l2_buffer flags
>   */
> -void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
> -		   struct v4l2_timecode tc, u32 offset, u32 flags);
> +int amvdec_add_ts(struct amvdec_session *sess, u64 ts,
> +		  struct v4l2_timecode tc, u32 offset, u32 flags);
>  void amvdec_remove_ts(struct amvdec_session *sess, u64 ts);
>  
>  /**
> 

Suggested-by: Neil Armstrong <narmstrong@...libre.com>
Reviewed-by: Neil Armstrong <narmstrong@...libre.com>

Neil