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

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On 3/25/24 1:50 PM, Greg Kroah-Hartman wrote:
On Mon, Mar 25, 2024 at 01:31:34PM -0500, Alex Elder wrote:
On 3/25/24 12:25 PM, Greg Kroah-Hartman wrote:
On Thu, Mar 07, 2024 at 09:48:13AM +0000, Rui Miguel Silva wrote:
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@xxxxxxxxxxxx

Fixes: 2870b52bae4c ("greybus: lights: add lights implementation")
Reported-by: Mikhail Lobanov <m.lobanov@xxxxxxxxxxxx>
Suggested-by: Mikhail Lobanov <m.lobanov@xxxxxxxxxxxx>
Suggested-by: Alex Elder <elder@xxxxxxxx>
Signed-off-by: Rui Miguel Silva <rmfrfs@xxxxxxxxx>
---
   drivers/staging/greybus/light.c | 6 +++++-
   1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c
index c6bd86a5335a..6f10b9e2c053 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 +552,8 @@ 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 (WARN_ON(!channel_flash))
+		return -EINVAL;

We should NOT crash machines just because of this, the WARN_ON() should
be removed and just properly handle the error please.

Greg, WARN_ON() doesn't normally crash the machine.  That said,
it's reasonable to remove the WARN_ON().

The huge majority of running Linux systems in the world run with
panic-on-warn enabled, including the one in your pocket :(

I did not know that.  Then WARN_ON() is no better than BUG_ON().
I'm still learning.  Thank you.

					-Alex

I think the purpose of the warning is that this is a case that
should "never happen," so if it does, it's making some noise.

Making noise by rebooting the box is not good.

thanks,

greg k-h





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