[PATCH v2] greybus: lights: check return of get_channel_from_mode

[Rui Miguel Silva <rmfrfs@gmail.com>]

If channel for the given node is not found we return null from
get_channel_from_mode. Make sure we validate the return pointer
before using it in two of the missing places.

This was originally reported in [0]:
Found by Linux Verification Center (linuxtesting.org) with SVACE.

[0] https://lore.kernel.org/all/20240301190425.120605-1-m.lobanov@rosalinux.ru

Fixes: 2870b52bae4c ("greybus: lights: add lights implementation")
Reported-by: Mikhail Lobanov <m.lobanov@rosalinux.ru>
Suggested-by: Mikhail Lobanov <m.lobanov@rosalinux.ru>
Suggested-by: Alex Elder <elder@ieee.org>
Signed-off-by: Rui Miguel Silva <rmfrfs@gmail.com>
---
v1[1] -> v2:
GregKh:
    - remove overkill WARN_ON and replace it for a dev_err

[1]: https://lore.kernel.org/all/20240307094838.688281-1-rmfrfs@gmail.com/

 drivers/staging/greybus/light.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c
index c6bd86a5335a..9999f8401699 100644
--- a/drivers/staging/greybus/light.c
+++ b/drivers/staging/greybus/light.c
@@ -147,6 +147,9 @@ static int __gb_lights_flash_brightness_set(struct gb_channel *channel)
 		channel = get_channel_from_mode(channel->light,
 						GB_CHANNEL_MODE_TORCH);
 
+	if (!channel)
+		return -EINVAL;
+
 	/* For not flash we need to convert brightness to intensity */
 	intensity = channel->intensity_uA.min +
 			(channel->intensity_uA.step * channel->led->brightness);
@@ -549,7 +552,10 @@ static int gb_lights_light_v4l2_register(struct gb_light *light)
 	}
 
 	channel_flash = get_channel_from_mode(light, GB_CHANNEL_MODE_FLASH);
-	WARN_ON(!channel_flash);
+	if (!channel_flash) {
+		dev_err(dev, "failed to get flash channel from mode\n");
+		return -EINVAL;
+	}
 
 	fled = &channel_flash->fled;
 
-- 
2.44.0