From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0208343893; Sat, 12 Sep 2026 13:31:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789219919; cv=none; b=QeIJKYB2/h22uYxz5bOJ9sQtBpkJA8BGiy1iQIbUEUYInUZjMR0+95QV3RHjisyFLbnyTEP13Ut128ALYlDfmQQAIYPnpFTFBAW4tU9MapKdlu7IVrwd1pqzuF61Ud5g4Y3FvGvD4TbRfGT3Q/usb3Acc1EMctS913WL1QEwAfc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789219919; c=relaxed/simple; bh=zewbqnXP7DTeeU5RWXZUkDOIwIupC5UlP0GkBQbuYJE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CXcuiZpAawFL5ULiMgIIM9HwIiBVY2Az7tKE8e4RisFwRfnsqHSOcYr2NDmaQ4SEr1fVE7QXa8ZdSfHatEQmNJ8nVY9GOv7gHkzVjhrJQWi1ByK6lJLW3pg0wYjYu+AZBSANNPVSTBkUAw9LSVnnZfG0QhDY5RN1fNFZbvk4zoc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=kcp94mYX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="kcp94mYX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A90FC1F000FF; Sat, 12 Sep 2026 13:31:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789219917; bh=MhIZJKi8jZBIFDXtrRiCGy4FL3/fSZVJBS7PPyhAwHo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kcp94mYXnj/Fy00w/Dx1pV8T3RIKwzhRZYZtYdWF6aj20vztZvrcVj8EHdl5NI2AS fdlcIcTEhnYfrqr84NVVQPI4JTOa9OWPyTKOaGBaNcHEyyA0Fxj/IKoprs12I2Dmkq uTe8I0VYk5fv/5U+eTP6X6YV22gc9+/2LfsfeXxY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Laurent Pinchart , Hans Verkuil Subject: [PATCH 6.6 0028/1424] Revert "media: v4l2-dev: fix error handling in __video_register_device()" Date: Sat, 12 Sep 2026 08:41:00 +0200 Message-ID: <20260912065607.935765771@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065607.279695368@linuxfoundation.org> References: <20260912065607.279695368@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hans Verkuil commit e7600f5cee5de14065f950807931d6e6d40fb2d7 upstream. This reverts commit 2a934fdb01db6458288fc9386d3d8ceba6dd551a. The intentions of that patch were good, but it doesn't work. The idea is that if device_register fails, you have to do a put_device to let the ref counter release resources. However, the V4L2 API says that if video_register_device() fails, then you have to call video_device_release(), which kfree()s the video_device struct. But the put_device() will already have freed the struct, so you end up in a double-free scenario. There is not really a good way of fixing this without breaking video_register_device() into two parts, one that initializes everything, and one that does the actual device_register, and then converting all V4L2 drivers to this new model. That is a massive job, and it is very unlikely that device_register will fail. So rather than ending up in a double-free scenario, just revert this patch, and in that case we'll have a small memory leak. Which is a lot more robust. Reviewed-by: Laurent Pinchart Fixes: 2a934fdb01db ("media: v4l2-dev: fix error handling in __video_register_device()") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-media/20260520090624.1071139-1-lgs201920130244@gmail.com/ Link: https://lore.kernel.org/all/2026042058-charm-storable-4ad8@gregkh/ Signed-off-by: Hans Verkuil Signed-off-by: Greg Kroah-Hartman --- drivers/media/v4l2-core/v4l2-dev.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) --- a/drivers/media/v4l2-core/v4l2-dev.c +++ b/drivers/media/v4l2-core/v4l2-dev.c @@ -1033,25 +1033,25 @@ int __video_register_device(struct video vdev->dev.class = &video_class; vdev->dev.devt = MKDEV(VIDEO_MAJOR, vdev->minor); vdev->dev.parent = vdev->dev_parent; - vdev->dev.release = v4l2_device_release; dev_set_name(&vdev->dev, "%s%d", name_base, vdev->num); - - /* Increase v4l2_device refcount */ - v4l2_device_get(vdev->v4l2_dev); - mutex_lock(&videodev_lock); ret = device_register(&vdev->dev); if (ret < 0) { mutex_unlock(&videodev_lock); pr_err("%s: device_register failed\n", __func__); - put_device(&vdev->dev); - return ret; + goto cleanup; } + /* Register the release callback that will be called when the last + reference to the device goes away. */ + vdev->dev.release = v4l2_device_release; if (nr != -1 && nr != vdev->num && warn_if_nr_in_use) pr_warn("%s: requested %s%d, got %s\n", __func__, name_base, nr, video_device_node_name(vdev)); + /* Increase v4l2_device refcount */ + v4l2_device_get(vdev->v4l2_dev); + /* Part 5: Register the entity. */ ret = video_register_media_controller(vdev);