[bug report] media: cx18: Access v4l2_fh from file

[Dan Carpenter <dan.carpenter@linaro.org>]

Hello Jacopo Mondi,

Commit 7b9eb53e8591 ("media: cx18: Access v4l2_fh from file") from
Aug 10, 2025 (linux-next), leads to the following Smatch static
checker warning:

drivers/media/pci/cx18/cx18-driver.c:1223 cx18_init_on_first_open() error: NULL dereference inside function
drivers/media/pci/cx18/cx18-driver.c:1229 cx18_init_on_first_open() error: NULL dereference inside function
drivers/media/pci/cx18/cx18-driver.c:1230 cx18_init_on_first_open() error: NULL dereference inside function
drivers/media/pci/ivtv/ivtv-driver.c:1313 ivtv_init_on_first_open() error: NULL dereference inside function
drivers/media/pci/ivtv/ivtv-driver.c:1319 ivtv_init_on_first_open() error: NULL dereference inside function

drivers/media/pci/cx18/cx18-driver.c
    1214         /* Set initial frequency. For PAL/SECAM broadcasts no
    1215            'default' channel exists AFAIK. */
    1216         if (cx->std == V4L2_STD_NTSC_M_JP)
    1217                 vf.frequency = 1460;        /* ch. 1 91250*16/1000 */
    1218         else if (cx->std & V4L2_STD_NTSC_M)
    1219                 vf.frequency = 1076;        /* ch. 4 67250*16/1000 */
    1220 
    1221         video_input = cx->active_input;
    1222         cx->active_input++;        /* Force update of input */
--> 1223         cx18_s_input(NULL, &fh, video_input);
                              ^^^^
The patch adds a new dereference of "file" but some of the callers pass a
NULL pointer.

    1224 
    1225         /* Let the VIDIOC_S_STD ioctl do all the work, keeps the code
    1226            in one place. */
    1227         cx->std++;                /* Force full standard initialization */
    1228         std = (cx->tuner_std == V4L2_STD_ALL) ? V4L2_STD_NTSC_M : cx->tuner_std;
    1229         cx18_s_std(NULL, &fh, std);
    1230         cx18_s_frequency(NULL, &fh, &vf);
    1231         return 0;
    1232 }

regards,
dan carpenter