linux-kernel - Re: [PATCH] PCI: endpoint: functions/pci-epf-test: Avoid DMA release when DMA is unsupported

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Message-ID: <948ae2b0-825e-4557-7e43-16d95d26e9f4@ti.com>
Date:   Wed, 22 Apr 2020 11:15:28 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: endpoint: functions/pci-epf-test: Avoid DMA release
 when DMA is unsupported

Hi Kunihiko,

On 3/23/2020 3:15 PM, Kunihiko Hayashi wrote:
> When unbinding pci_epf_test, pci_epf_test_clean_dma_chan() is called in
> pci_epf_test_unbind() even though epf_test->dma_supported is false.
> As a result, dma_release_channel() will occur null pointer access because
> dma_chan isn't set.
> 
> This avoids calling dma_release_channel() if epf_test->dma_supported
> is false.
> 
> Fixes: a1d105d4ab8e ("PCI: endpoint: functions/pci-epf-test: Add DMA support to transfer data")
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 3b4cf7e..8b4f136 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -609,7 +609,8 @@ static void pci_epf_test_unbind(struct pci_epf *epf)
>  	int bar;
>  
>  	cancel_delayed_work(&epf_test->cmd_handler);
> -	pci_epf_test_clean_dma_chan(epf_test);
> +	if (epf_test->dma_supported)
> +		pci_epf_test_clean_dma_chan(epf_test);

Can you add this check inside the pci_epf_test_clean_dma_chan()?

Thanks
Kishon