[PATCH net 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 using
skb_pull(skb, 2) and skb_trim(skb, len - ETH_FCS_LEN).

If the hardware reports a descriptor size smaller than the pad and CRC
lengths (e.g. runt or corrupted frames), len -= 2 or len - ETH_FCS_LEN
underflows u32 len, leading to out-of-bounds trimming and memory
corruption.

Check that desc->size is at least the sum of the 2-byte pad and the CRC
length 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..2ad8a7eac888 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 + (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