media: ivtv: Fix invalid access to file *

media: ivtv: Fix invalid access to file *

Since commit 9ba9d11544f9 ("media: ivtv: Access v4l2_fh from file")
all ioctl handlers have been ported to operate on the file * first
function argument.

The ivtv DVB layer calls ivtv_init_on_first_open() when the driver
needs to start streaming. This function calls the s_input() and
s_frequency() ioctl handlers directly, but being called from the driver
context, it doesn't have a valid file * to pass them. This causes the
ioctl handlers to deference an invalid pointer.

Fix this by moving the implementation of those ioctls to two helper
functions.

The ivtv_do_s_input() helper accepts a struct ivtv * as first argument,
which is easily accessible in ivtv_init_on_first_open() as well as from
the file * argument of the ioctl handler.

The ivtv_s_frequency() takes an ivtv_stream * instead. The stream * can
safely be accessed in ivtv_init_on_first_open() where it is hard-coded
to the IVTV_ENC_STREAM_TYPE_MPG stream type, as well as from the ioctl
handler as a valid stream type is associated to each open file handle
depending on which video device node has been opened in the ivtv_open()
file operation.

The bug has been reported by Smatch.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/aKL4OMWsESUdX8KQ@stanley.mountain/
Fixes: 9ba9d11544f9 ("media: ivtv: Access v4l2_fh from file")
Cc: stable@vger.kernel.org
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>