Re: [PATCH v3] media: meson: vdec: Fix a NULL pointer dereference in amvdec_add_ts()

[Hans Verkuil]

Zhou Qingyang, this is exactly the patch Neil wrote, except you just stuck your
name on it. Not nice.

Neil, can you post your patch with your own Signed-off-by, then I'll take that one.

Regards,

	Hans

On 15/12/2021 04:35, 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().
> 
> Fix this bug by adding a NULL check of new_ts.
> 
> This bug was found by a static analyzer[1].
> 
> 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@xxxxxxx>
> ---
> 
> [1] 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.
> 
> Changes in v3:
>   -  Change the description of patch
>   -  Turn the return type from 'void' to 'int'
>   -  Check the return value in the caller 'esparser_queue()'
> 
> Changes in v2:
>   -  Delete dev_err() 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..095100a50da8 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 b9125c295d1d..06fd66539797 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);
>  
>  /**