Patch "net: fec: handle page_pool_dev_alloc_pages error" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: fec: handle page_pool_dev_alloc_pages error

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-fec-handle-page_pool_dev_alloc_pages-error.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7c38868fc6519ce1066b30e5a4bda7acdb32b298
Author: Kevin Groeneveld <kgroeneveld@xxxxxxxxxxxx>
Date:   Mon Jan 13 10:48:45 2025 -0500

    net: fec: handle page_pool_dev_alloc_pages error
    
    [ Upstream commit 001ba0902046cb6c352494df610718c0763e77a5 ]
    
    The fec_enet_update_cbd function calls page_pool_dev_alloc_pages but did
    not handle the case when it returned NULL. There was a WARN_ON(!new_page)
    but it would still proceed to use the NULL pointer and then crash.
    
    This case does seem somewhat rare but when the system is under memory
    pressure it can happen. One case where I can duplicate this with some
    frequency is when writing over a smbd share to a SATA HDD attached to an
    imx6q.
    
    Setting /proc/sys/vm/min_free_kbytes to higher values also seems to solve
    the problem for my test case. But it still seems wrong that the fec driver
    ignores the memory allocation error and can crash.
    
    This commit handles the allocation error by dropping the current packet.
    
    Fixes: 95698ff6177b5 ("net: fec: using page pool to manage RX buffers")
    Signed-off-by: Kevin Groeneveld <kgroeneveld@xxxxxxxxxxxx>
    Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
    Reviewed-by: Wei Fang <wei.fang@xxxxxxx>
    Link: https://patch.msgid.link/20250113154846.1765414-1-kgroeneveld@xxxxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 9d9fcec41488e..49d1748e0c043 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1591,19 +1591,22 @@ static void fec_enet_tx(struct net_device *ndev, int budget)
 		fec_enet_tx_queue(ndev, i, budget);
 }
 
-static void fec_enet_update_cbd(struct fec_enet_priv_rx_q *rxq,
+static int fec_enet_update_cbd(struct fec_enet_priv_rx_q *rxq,
 				struct bufdesc *bdp, int index)
 {
 	struct page *new_page;
 	dma_addr_t phys_addr;
 
 	new_page = page_pool_dev_alloc_pages(rxq->page_pool);
-	WARN_ON(!new_page);
-	rxq->rx_skb_info[index].page = new_page;
+	if (unlikely(!new_page))
+		return -ENOMEM;
 
+	rxq->rx_skb_info[index].page = new_page;
 	rxq->rx_skb_info[index].offset = FEC_ENET_XDP_HEADROOM;
 	phys_addr = page_pool_get_dma_addr(new_page) + FEC_ENET_XDP_HEADROOM;
 	bdp->cbd_bufaddr = cpu_to_fec32(phys_addr);
+
+	return 0;
 }
 
 static u32
@@ -1698,6 +1701,7 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
 	int cpu = smp_processor_id();
 	struct xdp_buff xdp;
 	struct page *page;
+	__fec32 cbd_bufaddr;
 	u32 sub_len = 4;
 
 #if !defined(CONFIG_M5272)
@@ -1766,12 +1770,17 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
 
 		index = fec_enet_get_bd_index(bdp, &rxq->bd);
 		page = rxq->rx_skb_info[index].page;
+		cbd_bufaddr = bdp->cbd_bufaddr;
+		if (fec_enet_update_cbd(rxq, bdp, index)) {
+			ndev->stats.rx_dropped++;
+			goto rx_processing_done;
+		}
+
 		dma_sync_single_for_cpu(&fep->pdev->dev,
-					fec32_to_cpu(bdp->cbd_bufaddr),
+					fec32_to_cpu(cbd_bufaddr),
 					pkt_len,
 					DMA_FROM_DEVICE);
 		prefetch(page_address(page));
-		fec_enet_update_cbd(rxq, bdp, index);
 
 		if (xdp_prog) {
 			xdp_buff_clear_frags_flag(&xdp);