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 B2062388390; Fri, 11 Sep 2026 09:42:43 +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=1789119764; cv=none; b=CsXx1K9pkxizBYlIPEMCU1OWco3bYvEh3ALWNapWab4f8ZDKjLoX8e+YJN/hc2OFQ4wxzf4yNe7NVXWkHmQo337TYxBJBad38AkUaCA6S6DRP1WQMccAKui6zsGdHMU2PCg6QE0Z805jCK4mHxPPo+e7tmVn3FA6zdsyo1hmM4g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789119764; c=relaxed/simple; bh=CbXzt/YsttYc97x6bFX9LAYDKs2sjaJ+BssOCXFNnYU=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=qjedr+QDq8mvDN1HiwyltpElBWS3s0aJLkpaQ4774AIs4U2QEykEncqeoLSQBY/6sztJjhZH85UdkvHScZte30nhO3cURbBWQul2UzV0tLfkBNe0wwzzl3ojM50r0Fe9JfrUmhcPdjGe04AoqiqaN9psMALieCUmXqwZmPk0Y5w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HQcDqbdZ; 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="HQcDqbdZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DE6D1F00893; Fri, 11 Sep 2026 09:42:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789119763; bh=2ynPsvugMhUHUjQeW/PmhBGjSoS84MzCa/r1SyayhLc=; h=Date:From:Subject:To:Cc:References:In-Reply-To; b=HQcDqbdZcy2bRfS90b+Xtksw6BR7uo1pf85PnSra8aMgKNo6vq7lU2mjSSrlO2cAN 2e3dgOXawA7hYNV/n8Vz0LlwKz4CzwSfNtLykH1MDWJ3zPc5nJHWcGGIKI3KislqnF /GCzsaE/5FsUIPW/5gJE4U19GT1ocXJWhM7vHFZTQzj8RO5t24++6KefRxLv6IlDFb 23NxuRZX38kvZ8cnR8VhYU8rjXPRMeXkT79eQL/wl39KKTVoJdUX5FrzWcI494ajYI JeSlT5kffhqLhTaLuTA0SIDWSzBb/LPkXnnEOsLdAywrz9/N0GY86dPVxKF/WbVEZE ohTAFXMCmvlRw== Message-ID: Date: Fri, 11 Sep 2026 11:42:41 +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: Mauro Carvalho Chehab , Rokinthan p 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 [Resend, fixing a weird 'Reply-to' email, I hope it works this time) 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); >