[PATCH net v3 1/2] net/stmmac: Set Rx queue page_pool to NULL when freeing DMA resources

[Jakub Raczynski]

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.
Also remove NULL check as page_pool_destroy() does check for NULL param.

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>
Reviewed-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 2a0d7eff88d3..3098971e0b66 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2172,8 +2172,8 @@ 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)
-		page_pool_destroy(rx_q->page_pool);
+	page_pool_destroy(rx_q->page_pool);
+	rx_q->page_pool = NULL;
 }
 
 static void free_dma_rx_desc_resources(struct stmmac_priv *priv,
-- 
2.34.1