linux-kernel - Re: [RFC PATCH v7 6/9] media: tegra: Add Tegra210 Video input driver

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Message-ID: <31924f2b-8f85-d28d-4f5d-4e232bff94a5@nvidia.com>
Date:   Wed, 15 Apr 2020 16:08:16 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>
CC:     <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <frankc@...dia.com>, <hverkuil@...all.nl>, <sakari.ailus@....fi>,
        <helen.koike@...labora.com>, <sboyd@...nel.org>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v7 6/9] media: tegra: Add Tegra210 Video input driver

With minor change of not using vi reference after 
host1x_client_unregister and freeing vi during v4l2 device release works.

For csi, we can use devm_kzalloc for now untill we decide later if we 
want to expose async subdev nodes during sensor support.

Will have this fix in v8 with a comment in vi_remove to make sure not to 
use vi reference after host1x_client_unregister.

Will test more and will release v8 with above fix to allow direct host1x 
client driver unbind.

Thanks

sowjanya


On 4/15/20 12:51 PM, Sowjanya Komatineni wrote:
>
> On 4/15/20 12:21 PM, Dmitry Osipenko wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> 15.04.2020 21:53, Sowjanya Komatineni пишет:
>> ...
>>>>>>>>> Have you tried to test this driver under KASAN? I suspect that
>>>>>>>>> you just
>>>>>>>>> masked the problem, instead of fixing it.
>>> Tested with kmemleak scan and did not see any memory leaks
>> You should get use-after-free and not memleak.
> I don't see use-after-free bugs during the testing.
>
> But as mentioned when direct vi/csi client driver unbind happens while 
> video device node is kept opened, vi driver remove will free vi 
> structure memory but actual video device memory which is part of 
> channels remains but list head gets lost when vi structure is freed.
>
> So, when device node is released and executes release callback as list 
> head is lost it can't free allocated channels which is not good.
>
> This happens only with direct host1x client vi/csi driver unbind.
>
> Need to find better place to free host1x client driver data structure 
> to allow direct client driver unbind->bind.
>