[PATCH net 1/2] octeon_ep: fix skb frags overflow in the RX path

[Maoyi Xie <maoyixie.tju@gmail.com>]

__octep_oq_process_rx() builds an skb for a multi-buffer packet by adding
one fragment per buffer_size chunk:

	data_len = buff_info->len - oq->max_single_buffer_size;
	while (data_len) {
		...
		skb_add_rx_frag(skb, shinfo->nr_frags, buff_info->page, 0,
				buff_info->len, buff_info->len);
		...
	}

buff_info->len comes from the device response header
(be64_to_cpu(resp_hw->length)). Nothing bounds the fragment count against
MAX_SKB_FRAGS. data_len can be close to 65535. buffer_size defaults to
about 3776 on 4K pages, so a full packet yields about 18 fragments. That
is one more than the default MAX_SKB_FRAGS of 17, so skb_add_rx_frag()
writes past shinfo->frags[].

The driver now drops a packet that would need more fragments than the skb
can hold. octep_oq_drop_rx() consumes its descriptors, as on the build_skb
failure path. The same class was fixed in other RX paths, including
commit 5ffcb7b890f6 ("net: atlantic: fix fragment overflow handling in RX
path") and commit f0813bcd2d9d ("net: wwan: t7xx: fix potential skb->frags
overflow in RX path").

Fixes: 37d79d059606 ("octeon_ep: add Tx/Rx processing and interrupt support")
Co-developed-by: Kaixuan Li <kaixuan.li@ntu.edu.sg>
Signed-off-by: Kaixuan Li <kaixuan.li@ntu.edu.sg>
Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
---
 drivers/net/ethernet/marvell/octeon_ep/octep_rx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c b/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
index e6ebc7e44a00c..4ee911b6c0107 100644
--- a/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
+++ b/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
@@ -476,6 +476,12 @@ static int __octep_oq_process_rx(struct octep_device *oct,
 			skb_put(skb, oq->max_single_buffer_size);
 			shinfo = skb_shinfo(skb);
 			data_len = buff_info->len - oq->max_single_buffer_size;
+			if (DIV_ROUND_UP(data_len, oq->buffer_size) > MAX_SKB_FRAGS) {
+				dev_kfree_skb_any(skb);
+				octep_oq_drop_rx(oq, buff_info,
+						 &read_idx, &desc_used);
+				continue;
+			}
 			while (data_len) {
 				buff_info = (struct octep_rx_buffer *)
 					    &oq->buff_info[read_idx];
-- 
2.34.1