Re: [PATCH net] net/stmmac: Set Rx queue page_pool to NULL when freeing DMA resources

[Maxime Chevallier]

Hi,

On 6/30/26 12:09, Jakub Raczynski wrote:
> When freeing RX descriptor resources, there is standard clearing of
> descriptor page_pool via page_pool_destroy() which does destroy
> page but does not set its pointer to NULL, which must be done by driver
> calling this function.
> It is not done in __free_dma_rx_desc_resources() when stopping interface,
> which is generally not an issue, because __alloc_dma_rx_desc_resources() does
> setup this regardless of previous state.
> But above is true assuming reinitialization is successful.
> 
> In case of failure of page_pool_create() in __alloc_dma_rx_desc_resources(),
> all non-NULL pages will be freed, including those already cleared.
> So there is possible kernel panic due to wrong paging request at address.
> 
> Fix this by assigning NULL to page_pool pointer on free
> 
> Fixes: da5ec7f22a0f1 ("net: stmmac: refactor stmmac_init_rx_buffers for stmmac_reinit_rx_buffers")
> Signed-off-by: Yashwant Varur <yashwant.v@xxxxxxxxxxx>
> Signed-off-by: Jakub Raczynski <j.raczynski@xxxxxxxxxxx>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 3591755ea30b..4b8f2814d3b5 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -2172,8 +2172,10 @@ static void __free_dma_rx_desc_resources(struct stmmac_priv *priv,
>  		xdp_rxq_info_unreg(&rx_q->xdp_rxq);
>  
>  	kfree(rx_q->buf_pool);
> -	if (rx_q->page_pool)
> +	if (rx_q->page_pool) {
>  		page_pool_destroy(rx_q->page_pool);
> +		rx_q->page_pool = NULL;
> +	}

page_pool_destroy can be passed NULL, as you're fixing this I think you might as well
drop the if(rx_q->page_pool) at the same time :) I agree with the change otherwise.

with that changed,

Reviewed-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>

Maxime