linux-kernel - Re: [PATCH v4 01/14] dmaengine: tegra-apb: Fix use-after-free

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Date:   Tue, 14 Jan 2020 15:09:51 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
CC:     <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 01/14] dmaengine: tegra-apb: Fix use-after-free


On 12/01/2020 17:29, Dmitry Osipenko wrote:
> I was doing some experiments with I2C and noticed that Tegra APB DMA
> driver crashes sometime after I2C DMA transfer termination. The crash
> happens because tegra_dma_terminate_all() bails out immediately if pending
> list is empty, thus it doesn't release the half-completed descriptors
> which are getting re-used before ISR tasklet kicks-in.

Can you elaborate a bit more on how these are getting re-used? What is
the sequence of events which results in the panic? I believe that this
was also reported in the past [0] and so I don't doubt there is an issue
here, but would like to completely understand this.

Thanks!
Jon

[0] https://lore.kernel.org/patchwork/patch/675349/

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