[PATCH] net: wan: hd64572: validate RX length before skb allocation and copy

[Guangshuo Li]

The driver trusts the RX descriptor length and uses it directly for
dev_alloc_skb(), memcpy_fromio(), and skb_put() without any bounds
checking. If the descriptor gets corrupted or otherwise contains an
invalid value, this can lead to an excessive allocation or reading
past the per-buffer limit programmed by the driver.

Validate 'len' read from the descriptor and drop the frame if it is
zero or greater than HDLC_MAX_MRU. The driver programs BFLL to
HDLC_MAX_MRU for RX buffers, so this is the correct upper bound.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
---
 drivers/net/wan/hd64572.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wan/hd64572.c b/drivers/net/wan/hd64572.c
index 534369ffe5de..6327204e3c02 100644
--- a/drivers/net/wan/hd64572.c
+++ b/drivers/net/wan/hd64572.c
@@ -199,6 +199,12 @@ static inline void sca_rx(card_t *card, port_t *port, pkt_desc __iomem *desc,
 	u32 buff;
 
 	len = readw(&desc->len);
+
+	if (unlikely(!len || len > HDLC_MAX_MRU)) {
+		dev->stats.rx_length_errors++;
+		return;
+	}
+
 	skb = dev_alloc_skb(len);
 	if (!skb) {
 		dev->stats.rx_dropped++;
-- 
2.43.0