[PATCH net v2 3/6] net: bcmasp: validate minimum RX packet size in bcmasp_rx_poll()

[Florian Fainelli <florian.fainelli@broadcom.com>]

In bcmasp_rx_poll(), the driver removes a 2-byte alignment pad and
optionally strips the ETH_FCS_LEN CRC from received packets before
passing them to eth_type_trans().

If the hardware reports a descriptor size smaller than the sum of the
2-byte pad, the Ethernet header (ETH_HLEN), and optional CRC
(ETH_FCS_LEN), subtracting the pad and CRC lengths underflows u32 len.
This adds ~4 GiB to rx_bytes statistics, while the undersized frame
reaches eth_type_trans(), which reads past skb->len into stale buffer
data.

Check that desc->size is at least (2 + ETH_HLEN + (crc_fwd ? ETH_FCS_LEN
: 0)) before proceeding to process the descriptor.

Fixes: 490cb412007d ("net: bcmasp: Add support for ASP2.0 Ethernet controller")
Assisted-by: LLM
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c b/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c
index 9ad5a982542f..d679c796c8c2 100644
--- a/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c
+++ b/drivers/net/ethernet/broadcom/asp2/bcmasp_intf.c
@@ -523,6 +523,12 @@ static int bcmasp_rx_poll(struct napi_struct *napi, int budget)
 					DMA_FROM_DEVICE);
 
 		len = desc->size;
+		if (unlikely(len < 2 + ETH_HLEN + (intf->crc_fwd ? ETH_FCS_LEN : 0))) {
+			u64_stats_update_begin(&stats->syncp);
+			u64_stats_inc(&stats->rx_dropped);
+			u64_stats_update_end(&stats->syncp);
+			goto next;
+		}
 
 		/* Allocate a page pool page as the SKB data area so the
 		 * kernel can recycle it efficiently after the packet is
-- 
2.34.1