linux-kernel - Re: [PATCH v2] staging: greybus: lights: avoid NULL deref

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Message-ID: <2026010824-debtless-junior-4d18@gregkh>
Date: Thu, 8 Jan 2026 12:17:18 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Chaitanya Mishra <chaitanyamishra.ai@...il.com>
Cc: rmfrfs@...il.com, johan@...nel.org, elder@...nel.org,
	greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] staging: greybus: lights: avoid NULL deref

On Thu, Jan 08, 2026 at 04:33:51PM +0530, Chaitanya Mishra wrote:
> Hi Greg,
> 
> Found by manual code review while walking the error paths in
> Gb_lights_light_config(): channels_count is set before channels
> allocation, but cleanup uses channels_count to iterate and dereference
> light->channels. If kcalloc() fails, that becomes a NULL deref.

Might I ask why are you manually reviewing the error code paths of this
driver?  Do you have this hardware somewhere?

> Fix is simply deferring channels_count publication until after the
> allocation succeeds; v2 includes the requested comment.
> 
> Tested with:
>   ./scripts/checkpatch.pl --strict -g HEAD
>   ./scripts/checkpatch.pl outgoing/0001-staging-greybus-lights-avoid-NULL-deref.patch
> 
> I couldn't build-test locally on macOS due to missing <elf.h> for
> kernel host tools.

For obvious reasons, sending out patches that you didn't even build test
is probably not a good idea :)

thanks,

greg k-h