From patchwork Fri Feb 23 08:45:36 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans Verkuil X-Patchwork-Id: 775784 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2684A134B7 for ; Fri, 23 Feb 2024 08:45:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708677939; cv=none; b=bJTbvO62CBqsjZMrlXtuBVzGCaZp89/Bm9+7i6R4c+kpQGNr8ZRcSefnQUBw1Tx3YTcKrsD1/yYY9Vr3Jv4xfxmKnN9HE+wBhV+pHYaNL9FESdr7fGTjPly5JUHru7qlIzxkhRS94clLSXnaXcepSqnPCWWolz7OkvFRlwNxd9I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708677939; c=relaxed/simple; bh=AhKVSJr7f7GwzoW25mRJ1tF+k4CW9qLExycglRYAyTg=; h=Message-ID:Date:MIME-Version:To:From:Subject:Content-Type; b=W+BCn3RqbC0dPL9puh836IInELxDUW8XcU1WQGlb8btbHxOChsBFAVkuF6BTl6Dw+mWj1uJdqIOVBHUTKVp63RPWsOGSRv7YMyS0ynnwNBh1EzgGpBcy8+7za4OO8Vo/DjuZWxdyhYgJkX8E0iqLpQtLgSfUZBtIdWqHadUYc+0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68BD3C43390 for ; Fri, 23 Feb 2024 08:45:38 +0000 (UTC) Message-ID: <50f691d3-f49b-4279-9048-48319afd86f9@xs4all.nl> Date: Fri, 23 Feb 2024 09:45:36 +0100 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US, nl To: Linux Media Mailing List From: Hans Verkuil Subject: [PATCH] media: v4l2-core: hold videodev_lock until dev reg, finishes After the new V4L2 device node was registered, some additional initialization was done before the device node was marked as 'registered'. During the time between creating the device node and marking it as 'registered' it was possible to open the device node, which would return -ENODEV since the 'registered' flag was not yet set. Hold the videodev_lock mutex from just before the device node is registered until the 'registered' flag is set. Since v4l2_open will take the same lock, it will wait until this registration process is finished. This resolves this race condition. Signed-off-by: Hans Verkuil Reviewed-by: Sakari Ailus --- drivers/media/v4l2-core/v4l2-dev.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c index d13954bd31fd..bae73b8c52ff 100644 --- a/drivers/media/v4l2-core/v4l2-dev.c +++ b/drivers/media/v4l2-core/v4l2-dev.c @@ -1036,8 +1036,10 @@ int __video_register_device(struct video_device *vdev, vdev->dev.devt = MKDEV(VIDEO_MAJOR, vdev->minor); vdev->dev.parent = vdev->dev_parent; dev_set_name(&vdev->dev, "%s%d", name_base, vdev->num); + mutex_lock(&videodev_lock); ret = device_register(&vdev->dev); if (ret < 0) { + mutex_unlock(&videodev_lock); pr_err("%s: device_register failed\n", __func__); goto cleanup; } @@ -1057,6 +1059,7 @@ int __video_register_device(struct video_device *vdev, /* Part 6: Activate this minor. The char device can now be used. */ set_bit(V4L2_FL_REGISTERED, &vdev->flags); + mutex_unlock(&videodev_lock); return 0;