linux-kernel - [PATCH v4] staging: greybus: lights: avoid NULL deref

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Message-ID: <20260108151254.81553-1-chaitanyamishra.ai@gmail.com>
Date: Thu,  8 Jan 2026 20:42:54 +0530
From: Chaitanya Mishra <chaitanyamishra.ai@...il.com>
To: rmfrfs@...il.com,
	johan@...nel.org,
	elder@...nel.org,
	gregkh@...uxfoundation.org
Cc: greybus-dev@...ts.linaro.org,
	linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Chaitanya Mishra <chaitanyamishra.ai@...il.com>,
	Rui Miguel Silva <rui.silva@...aro.org>
Subject: [PATCH v4] staging: greybus: lights: avoid NULL deref

gb_lights_light_config() stores channel_count before allocating the
channels array. If kcalloc() fails, gb_lights_release() iterates the
non-zero count and dereferences light->channels, which is NULL.

Allocate channels first and only then publish channels_count so the
cleanup path can't walk a NULL pointer.

Fixes: 2870b52bae4c ("greybus: lights: add lights implementation")
Link: https://lore.kernel.org/all/20260108103700.15384-1-chaitanyamishra.ai@gmail.com/
Reviewed-by: Rui Miguel Silva <rui.silva@...aro.org>
Signed-off-by: Chaitanya Mishra <chaitanyamishra.ai@...il.com>
---
Changes in v4:
- Add Link to v1 and carry Reviewed-by.
- Tested: make defconfig, make modules_prepare, make M=drivers/staging/greybus/ modules (AWS EC2 eu-central-2, Amazon Linux 2023 x86_64).

Changes in v3:
- Add version changelog below the --- line (no code changes).

 drivers/staging/greybus/light.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c
index e509fdc715db..38c233a706c4 100644
--- a/drivers/staging/greybus/light.c
+++ b/drivers/staging/greybus/light.c
@@ -1008,14 +1008,18 @@ static int gb_lights_light_config(struct gb_lights *glights, u8 id)
 	if (!strlen(conf.name))
 		return -EINVAL;
 
-	light->channels_count = conf.channel_count;
 	light->name = kstrndup(conf.name, NAMES_MAX, GFP_KERNEL);
 	if (!light->name)
 		return -ENOMEM;
-	light->channels = kcalloc(light->channels_count,
+	light->channels = kcalloc(conf.channel_count,
 				  sizeof(struct gb_channel), GFP_KERNEL);
 	if (!light->channels)
 		return -ENOMEM;
+	/*
+	 * Publish channels_count only after channels allocation so cleanup
+	 * doesn't walk a NULL channels pointer on allocation failure.
+	 */
+	light->channels_count = conf.channel_count;
 
 	/* First we collect all the configurations for all channels */
 	for (i = 0; i < light->channels_count; i++) {
-- 
2.50.1 (Apple Git-155)