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 A73513C1F41; Fri, 11 Sep 2026 09:40:28 +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=1789119630; cv=none; b=pMmsJBLC25p8NehmjSD6ES2vY61wSdMvJzfI7vmbofbSZ4G/l663q9vZR6ZeiHJVHJVd+ufycpYdSm8TyNxEJT4KnK7DJVUad1NCW+o0hhGjbFN81reAbmcf/vgWrfmB15GJZ0wu1Ft4Y7d8uBwK4lBQGAQDaZduOlUC4UK2RKw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789119630; c=relaxed/simple; bh=/KC7R7LCZQTfEzVBjmlS82pJlzezG0lFxsDmrB7OLzI=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=jySGlDQLWZM430TMuZOUZWY23HpPzpgSIqJpRo9UncZMbClBj4+ssUeCpmPy3kktW7QuXl7upweNtsOvb+57tHTFPiz/DgdoWvFThEkJr5swdZ6RxcNYXHdoqrSJ5z7ZI75rEHAo3XwHYP88wIOjYDaQBn2nLYX2a60NZ1jskvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dkS/kfNm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dkS/kfNm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00C711F000FF; Fri, 11 Sep 2026 09:40:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789119628; bh=qtZkghSZqu20Hq3t2720b87ibjy+DNc4eCpTzFGg04U=; h=Date:From:Subject:To:Cc:References:In-Reply-To; b=dkS/kfNm4gwGB5AtHoQG/vzOfuusSJH9xRU4l5jjsdbr92KVaHQJ16JTFraxH3LqK Z3zuJ8eZfklJPXIVu5wpQSUas+pif0UCocWFlQu2yDbTH1dpesrvtqDB96ipv5H5de agqNqkNWH3bCCk5lYuDdvb9hmm2xS/T/iAzDg5xP8Plv4NZ3H+gn/KuB8RLiKqMXBq nUaEKyaujXKF2D//wecQNrxzboKSlQW4GhZMJg/G1oXEYD540NPohF2upF4F2H4c0C S4dQKu5IiUI13IEomONrZ6JLokMATUOxwkuSa+AxrAdKy5wKnSNKNPro4RVKR+bD+U sEYMM8A0vSBlg== Message-ID: <91922aca-20dc-4e17-b380-ac74c61bd3c7@kernel.org> Date: Fri, 11 Sep 2026 11:40:24 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Hans Verkuil Subject: Re: [PATCH v2] media: hackrf: defer v4l2_ctrl_auto_cluster() until after error check To: www.rokinthanp03@gmail.com, Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, cf896de36144391bcde1@syzkaller.appspotmail.com, syzbot+9f7405999979761b6cfc@syzkaller.appspotmail.com References: Content-Language: en-US, nl In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Rokinthan, On 10/09/2026 16:26, Rokinthan p wrote: > In hackrf_probe(), v4l2_ctrl_auto_cluster() is called immediately after > allocating the auto and manual bandwidth controls for both the receiver > and transmitter. > > If allocating the master control (dev->rx_bandwidth_auto or > dev->tx_bandwidth_auto) fails, e.g. due to memory allocation failure, > the pointer is NULL and the error is recorded in the control handler. > Calling v4l2_ctrl_auto_cluster() with a NULL master control causes > v4l2_ctrl_cluster() to trigger a WARNING: > > ncontrols == 0 || controls[0] == NULL > WARNING: drivers/media/v4l2-core/v4l2-ctrls-core.c:2525 at > v4l2_ctrl_cluster > > Fix this by moving the v4l2_ctrl_auto_cluster() invocations down after > checking dev->rx_ctrl_handler.error and dev->tx_ctrl_handler.error. > If control allocation fails, probe cleanly aborts with an error without > attempting to cluster NULL controls. Your analysis is correct, but the fix should actually be done in the v4l2-ctrls-core.c source. If controls[0] is NULL, then both v4l2_ctrl_cluster and v4l2_ctrl_auto_cluster should just return 0 since something clearly went wrong when the master control was created. This will be caught at the end in the driver code when hdl->error is checked. The code snippet for Control Clusters in Documentation/driver-api/media/v4l2-controls.rst clearly shows that that was how it was intended (i.e. state->audio_cluster[0] might be NULL, but it is still passed without checking to v4l2_ctrl_cluster). The design has always been that you can just create controls as you go and just check for hdl->error at the end. It saves a lot of unnecessary checks. And v4l2_ctrl_cluster/v4l2_ctrl_auto_cluster break that scheme. So can you make a patch that adds that NULL pointer check? And also update the function documentation in include/media/v4l2-ctrls.h to make it clear it just returns if controls[0] == NULL. Fixing this in hackrf just papers over the root cause, and there are almost certainly more drivers that do not check the master control before calling v4l2_ctrl_cluster/v4l2_ctrl_auto_cluster. And BTW, your patch is still mangled. Regards, Hans > > Fixes: 969ec1f6bd92 ("[media] hackrf: HackRF SDR driver") > Reported-by: syzbot+cf896de36144391bcde1@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=cf896de36144391bcde1 > Signed-off-by: Rohinthan > --- > v1 -> v2: > - Correct the Fixes tag commit hash and title to match git history > - Fix email formatting and whitespace > > drivers/media/usb/hackrf/hackrf.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/usb/hackrf/hackrf.c > b/drivers/media/usb/hackrf/hackrf.c > --- a/drivers/media/usb/hackrf/hackrf.c > +++ b/drivers/media/usb/hackrf/hackrf.c > @@ -1427,7 +1427,6 @@ static int hackrf_probe(struct usb_interface *intf, > dev->rx_bandwidth = v4l2_ctrl_new_std(&dev->rx_ctrl_handler, > &hackrf_ctrl_ops_rx, V4L2_CID_RF_TUNER_BANDWIDTH, > 1750000, 28000000, 50000, 1750000); > - v4l2_ctrl_auto_cluster(2, &dev->rx_bandwidth_auto, 0, false); > dev->rx_rf_gain = v4l2_ctrl_new_std(&dev->rx_ctrl_handler, > &hackrf_ctrl_ops_rx, V4L2_CID_RF_TUNER_RF_GAIN, 0, 12, > 12, 0); > dev->rx_lna_gain = v4l2_ctrl_new_std(&dev->rx_ctrl_handler, > @@ -1439,6 +1438,7 @@ static int hackrf_probe(struct usb_interface *intf, > dev_err(dev->dev, "Could not initialize controls\n"); > goto err_v4l2_ctrl_handler_free_rx; > } > + v4l2_ctrl_auto_cluster(2, &dev->rx_bandwidth_auto, 0, false); > v4l2_ctrl_grab(dev->rx_rf_gain, !hackrf_enable_rf_gain_ctrl); > v4l2_ctrl_handler_setup(&dev->rx_ctrl_handler); > > @@ -1450,7 +1450,6 @@ static int hackrf_probe(struct usb_interface *intf, > dev->tx_bandwidth = v4l2_ctrl_new_std(&dev->tx_ctrl_handler, > &hackrf_ctrl_ops_tx, V4L2_CID_RF_TUNER_BANDWIDTH, > 1750000, 28000000, 50000, 1750000); > - v4l2_ctrl_auto_cluster(2, &dev->tx_bandwidth_auto, 0, false); > dev->tx_lna_gain = v4l2_ctrl_new_std(&dev->tx_ctrl_handler, > &hackrf_ctrl_ops_tx, V4L2_CID_RF_TUNER_LNA_GAIN, 0, 47, > 1, 0); > dev->tx_rf_gain = v4l2_ctrl_new_std(&dev->tx_ctrl_handler, > @@ -1460,6 +1459,7 @@ static int hackrf_probe(struct usb_interface *intf, > dev_err(dev->dev, "Could not initialize controls\n"); > goto err_v4l2_ctrl_handler_free_tx; > } > + v4l2_ctrl_auto_cluster(2, &dev->tx_bandwidth_auto, 0, false); > v4l2_ctrl_grab(dev->tx_rf_gain, !hackrf_enable_rf_gain_ctrl); > v4l2_ctrl_handler_setup(&dev->tx_ctrl_handler); >