linux-kernel - [PATCH] comedi: fix device lifecycle handling in comedi_dev_kref

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Message-ID: <20260130223517.223996-1-salah.triki@gmail.com>
Date: Fri, 30 Jan 2026 23:35:17 +0100
From: Salah Triki <salah.triki@...il.com>
To: Ian Abbott <abbotti@....co.uk>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>
Cc: linux-kernel@...r.kernel.org,
	Salah Triki <salah.triki@...il.com>
Subject: [PATCH] comedi: fix device lifecycle handling in comedi_dev_kref_release()

`comedi_dev_kref_release()` calls `put_device()` on `dev->class_dev` and
then immediately frees the `comedi_device` structure with `kfree()`.
If the device reference count reaches zero, the device model release
callback may be invoked, potentially accessing or freeing parts of
the structure. Calling `kfree()` directly after `put_device()` can
cause a use-after-free or double-free.

After `device_initialize()` and once the struct device is in the device
model, all cleanup must go through `put_device()` and the release
callback. The kref release should not free the structure directly,
ensuring that `comedi_device` lifetime is properly managed through
device reference counting and preventing potential memory corruption.

Fixes: 5b13ed94a7d24 ("staging: comedi: add a kref to comedi device")

Signed-off-by: Salah Triki <salah.triki@...il.com>
---
 drivers/comedi/comedi_fops.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c
index 2c3eb9e89571..24bb06fe6b45 100644
--- a/drivers/comedi/comedi_fops.c
+++ b/drivers/comedi/comedi_fops.c
@@ -118,7 +118,6 @@ static void comedi_dev_kref_release(struct kref *kref)

 	mutex_destroy(&dev->mutex);
 	put_device(dev->class_dev);
-	kfree(dev);
 }

 /**
-- 
2.43.0