Re: [PATCH] PCI: endpoint: pci-epf-test: NULL check dma channels before release

[Damien Le Moal <dlemoal@kernel.org>]

On 9/12/25 16:11, Shin'ichiro Kawasaki wrote:
> When endpoint controller driver is immature, the fields dma_chan_tx and
> dma_chan_rx of the struct pci_epf_test could be NULL even after epf
> initialization. However, pci_epf_test_clean_dma_chan() assumes that they
> are always non-NULL valid values, and causes kernel panic when the
> fields are NULL. To avoid the kernel panic, NULL check the fields before
> release.
> 
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> ---
>  drivers/pci/endpoint/functions/pci-epf-test.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index e091193bd8a8..1c29d5dd4382 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -301,15 +301,20 @@ static void pci_epf_test_clean_dma_chan(struct pci_epf_test *epf_test)
>  	if (!epf_test->dma_supported)
>  		return;
>  
> -	dma_release_channel(epf_test->dma_chan_tx);
> -	if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
> +	if (epf_test->dma_chan_tx) {
> +		dma_release_channel(epf_test->dma_chan_tx);
> +		if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
> +			epf_test->dma_chan_tx = NULL;
> +			epf_test->dma_chan_rx = NULL;
> +			return;
> +		}
>  		epf_test->dma_chan_tx = NULL;
> -		epf_test->dma_chan_rx = NULL;
> -		return;
>  	}

Can we simplify here ?

	if (epf_test->dma_chan_tx) {
		dma_release_channel(epf_test->dma_chan_tx);
		epf_test->dma_chan_tx = NULL;
		if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
			epf_test->dma_chan_rx = NULL;
			return;
		}
	}

>  
> -	dma_release_channel(epf_test->dma_chan_rx);
> -	epf_test->dma_chan_rx = NULL;
> +	if (epf_test->dma_chan_rx) {
> +		dma_release_channel(epf_test->dma_chan_rx);
> +		epf_test->dma_chan_rx = NULL;
> +	}
>  }
>  
>  static void pci_epf_test_print_rate(struct pci_epf_test *epf_test,


-- 
Damien Le Moal
Western Digital Research