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 30B69402B8C; Fri, 4 Sep 2026 05:41:16 +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=1788500477; cv=none; b=oTBMYT11XOSQQB3QHbtzZf4pjqZCvUSCDtf/Lfgd4d/OWfdpAy28EgTaFkoLFHZY+acDFJqbW0wu+hYeTfTB6SWNDA91BP3pkCVYsMbQ77O5Og8DM2DCs48F7ih9FlXCTETskcWJoqvfiIISho6ITmNinuS1vQ53ft/hJn0o/tY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500477; c=relaxed/simple; bh=Z5Lc30YtLkFp8NlSh17PfVedw1lK8g4cOn86UsN8FZw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kfrEqCxedBtYQwpkuAaXRiKf6aN+zdiYMPU1mGkHiHHcpg1OCDw3Q7TR/H9/q8Bdgv5xQHfAKjmuWAEhG4Bh55hSbTPno3B1Qrotm6KZKCVjuRq63v5id5IKovqR0VHX//LCi8aud/uAyVN5Wt/Dcl1HpWgpbUNLpeyTHPdvpHA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XsvFe7by; 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="XsvFe7by" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8414A1F00A3D; Fri, 4 Sep 2026 05:41:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788500476; bh=RRhc/9P1IwHl4jXBAlWZfgjD1LJJjApfBGWhT1YcE+Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XsvFe7byO7/Imi1t0T1TjcJ19uTngJZuWMn0uq4x1S+cgW30e3R5s+vfZ+TehIIrP 9tkwlt+k0qJBYZmrogZa6/CuvJ2uVDNyeWeFNqV7/hMC4nivOn6U1hT8vV7SLGG0Ay JqPk6E8S4qDWd1tuy/cH/hvFdVRwr8ddRId7JETo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Laurent Pinchart , Hans Verkuil Subject: [PATCH 6.18 068/552] Revert "media: v4l2-dev: fix error handling in __video_register_device()" Date: Fri, 4 Sep 2026 06:53:45 +0200 Message-ID: <20260904045749.391331117@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@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 6.18-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 @@ -1066,25 +1066,25 @@ 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);