Re: [PATCH v4 1/5] media: uvc: Ignore empty TS packets

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Hi Ricardo,

url:    https://github.com/intel-lab-lkp/linux/commits/Ricardo-Ribalda/media-uvc-Ignore-empty-TS-packets/20230109-180318
base:   73d6709376914f577a61bb29e596fa93ec66598c
patch link:    https://lore.kernel.org/r/20220920-resend-hwtimestamp-v4-1-a8ddc1358a29%40chromium.org
patch subject: [PATCH v4 1/5] media: uvc: Ignore empty TS packets
config: arc-randconfig-m031-20230108
compiler: arceb-elf-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <error27@xxxxxxxxx>

smatch warnings:
drivers/media/usb/uvc/uvc_video.c:538 uvc_video_clock_decode() error: we previously assumed 'buf' could be null (see line 514)

vim +/buf +538 drivers/media/usb/uvc/uvc_video.c

66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  469  static void
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  470  uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
2c6b222cee2d68e drivers/media/usb/uvc/uvc_video.c   Laurent Pinchart 2018-01-16  471  		       const u8 *data, int len)
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  472  {
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  473  	struct uvc_clock_sample *sample;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  474  	unsigned int header_size;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  475  	bool has_pts = false;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  476  	bool has_scr = false;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  477  	unsigned long flags;
828ee8c71950155 drivers/media/usb/uvc/uvc_video.c   Arnd Bergmann    2017-11-27  478  	ktime_t time;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  479  	u16 host_sof;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  480  	u16 dev_sof;
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  481  	u32 dev_stc;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  482  
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  483  	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  484  	case UVC_STREAM_PTS | UVC_STREAM_SCR:
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  485  		header_size = 12;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  486  		has_pts = true;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  487  		has_scr = true;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  488  		break;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  489  	case UVC_STREAM_PTS:
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  490  		header_size = 6;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  491  		has_pts = true;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  492  		break;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  493  	case UVC_STREAM_SCR:
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  494  		header_size = 8;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  495  		has_scr = true;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  496  		break;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  497  	default:
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  498  		header_size = 2;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  499  		break;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  500  	}
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  501  
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  502  	/* Check for invalid headers. */
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  503  	if (len < header_size)
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  504  		return;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  505  
699b9a86a3f03ad drivers/media/usb/uvc/uvc_video.c   Laurent Pinchart 2022-06-08  506  	/*
699b9a86a3f03ad drivers/media/usb/uvc/uvc_video.c   Laurent Pinchart 2022-06-08  507  	 * Extract the timestamps:
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  508  	 *
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  509  	 * - store the frame PTS in the buffer structure
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  510  	 * - if the SCR field is present, retrieve the host SOF counter and
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  511  	 *   kernel timestamps and store them with the SCR STC and SOF fields
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  512  	 *   in the ring buffer
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  513  	 */
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24 @514  	if (has_pts && buf != NULL)
                                                                                                       ^^^^^^^^^^^
This code checks for NULL.

66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  515  		buf->pts = get_unaligned_le32(&data[2]);
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  516  
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  517  	if (!has_scr)
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  518  		return;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  519  
699b9a86a3f03ad drivers/media/usb/uvc/uvc_video.c   Laurent Pinchart 2022-06-08  520  	/*
699b9a86a3f03ad drivers/media/usb/uvc/uvc_video.c   Laurent Pinchart 2022-06-08  521  	 * To limit the amount of data, drop SCRs with an SOF identical to the
a919bd4d768164c drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-04  522  	 * previous one. This filtering is also needed to support UVC 1.5, where
a919bd4d768164c drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-04  523  	 * all the data packets of the same frame contains the same SOF. In that
a919bd4d768164c drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-04  524  	 * case only the first one will match the host_sof.
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  525  	 */
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  526  	dev_sof = get_unaligned_le16(&data[header_size - 2]);
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  527  	if (dev_sof == stream->clock.last_sof)
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  528  		return;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  529  
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  530  	dev_stc = get_unaligned_le32(&data[header_size - 6]);
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  531  
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  532  	/*
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  533  	 * Some devices make a borderline interpretation of the UVC 1.5 standard
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  534  	 * and sends packets with no data contain undefined timestamps. Ignore
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  535  	 * such packages to avoid interfering with the clock interpolation
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  536  	 * algorithm.
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  537  	 */
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09 @538  	if (buf->bytesused == 0 && len == header_size &&
                                                                                            ^^^^^^^^^^^^^^
Unchecked dereference

febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  539  	    dev_stc == 0 && dev_sof == 0)
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  540  		return;
febd4163e286059 drivers/media/usb/uvc/uvc_video.c   Ricardo Ribalda  2023-01-09  541  
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  542  	stream->clock.last_sof = dev_sof;
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  543  
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  544  	host_sof = usb_get_current_frame_number(stream->dev->udev);
828ee8c71950155 drivers/media/usb/uvc/uvc_video.c   Arnd Bergmann    2017-11-27  545  	time = uvc_video_get_time();
66847ef013cc4ed drivers/media/video/uvc/uvc_video.c Laurent Pinchart 2011-09-24  546  
699b9a86a3f03ad drivers/media/usb/uvc/uvc_video.c   Laurent Pinchart 2022-06-08  547  	/*

-- 
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