Re: [PATCH] net: netcp: Fix crash in error path when DMA channel open fails

[Simon Horman <horms@kernel.org>]

On Fri, Sep 26, 2025 at 10:08:53AM -0500, Nishanth Menon wrote:
> When knav_dma_open_channel() fails in netcp_setup_navigator_resources(),
> the rx_channel field is set to an ERR_PTR value. Later, when
> netcp_free_navigator_resources() is called in the error path, it attempts
> to close this invalid channel pointer, causing a crash.
> 
> Add a check for ERR values to handle the failure scenario.
> 
> Fixes: 84640e27f230 ("net: netcp: Add Keystone NetCP core driver")
> Signed-off-by: Nishanth Menon <nm@ti.com>
> ---
> 
> Seen on kci log for k2hk: https://dashboard.kernelci.org/log-viewer?itemId=ti%3A2eb55ed935eb42c292e02f59&org=ti&type=test&url=http%3A%2F%2Ffiles.kernelci.org%2F%2Fti%2Fmainline%2Fmaster%2Fv6.17-rc7-59-gbf40f4b87761%2Farm%2Fmulti_v7_defconfig%2BCONFIG_EFI%3Dy%2BCONFIG_ARM_LPAE%3Dy%2Bdebug%2Bkselftest%2Btinyconfig%2Fgcc-12%2Fbaseline-nfs-boot.nfs-k2hk-evm.txt.gz
> 
>  drivers/net/ethernet/ti/netcp_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/ti/netcp_core.c b/drivers/net/ethernet/ti/netcp_core.c
> index 857820657bac..4ff17fd6caae 100644
> --- a/drivers/net/ethernet/ti/netcp_core.c
> +++ b/drivers/net/ethernet/ti/netcp_core.c
> @@ -1549,7 +1549,7 @@ static void netcp_free_navigator_resources(struct netcp_intf *netcp)
>  {
>  	int i;
>  
> -	if (netcp->rx_channel) {
> +	if (!IS_ERR(netcp->rx_channel)) {
>  		knav_dma_close_channel(netcp->rx_channel);
>  		netcp->rx_channel = NULL;
>  	}

Hi Nishanth,

Thanks for your patch.

I expect that netcp_txpipe_close() has a similar problem too.

But I also think that using IS_ERR is not correct, because it seems to me
that there are also cases where rx_channel can be NULL.

I see that on error knav_dma_open_channel() always returns ERR_PTR(-EINVAL)
(open coded as (void *)-EINVAL) on error. So I think a better approach
would be to change knav_dma_open_channel() to return NULL, and update callers
accordingly.