[PATCH net v2 2/2] octeon_ep_vf: fix skb frags overflow in the RX path

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

__octep_vf_oq_process_rx() has the same unbounded fragment loop as the PF
driver. buff_info->len comes from the device response header, and one
fragment is added per buffer_size chunk with no check against
MAX_SKB_FRAGS. A long packet yields about 18 fragments, one past the
default MAX_SKB_FRAGS of 17, so skb_add_rx_frag() writes past
shinfo->frags[].

The fragment count is now checked before napi_build_skb(). A packet that
needs more fragments than the skb can hold is dropped. Its descriptors are
drained the same way the build_skb failure path does.

Fixes: 1cd3b407977c ("octeon_ep_vf: 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>
---
 .../marvell/octeon_ep_vf/octep_vf_rx.c        | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c
index d982474082..7af6a80671 100644
--- a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c
+++ b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c
@@ -431,6 +431,26 @@ static int __octep_vf_oq_process_rx(struct octep_vf_device *oct,
 			struct skb_shared_info *shinfo;
 			u16 data_len;
 
+			data_len = buff_info->len - oq->max_single_buffer_size;
+			if (DIV_ROUND_UP(data_len, oq->buffer_size) > MAX_SKB_FRAGS) {
+				desc_used++;
+				read_idx = octep_vf_oq_next_idx(oq, read_idx);
+				while (data_len) {
+					dma_unmap_page(oq->dev, oq->desc_ring[read_idx].buffer_ptr,
+						       PAGE_SIZE, DMA_FROM_DEVICE);
+					buff_info = (struct octep_vf_rx_buffer *)
+						    &oq->buff_info[read_idx];
+					buff_info->page = NULL;
+					if (data_len < oq->buffer_size)
+						data_len = 0;
+					else
+						data_len -= oq->buffer_size;
+					desc_used++;
+					read_idx = octep_vf_oq_next_idx(oq, read_idx);
+				}
+				continue;
+			}
+
 			skb = napi_build_skb((void *)resp_hw, PAGE_SIZE);
 			if (!skb) {
 				oq->stats->alloc_failures++;
-- 
2.34.1