[PATCH net v3 2/4] net: mvpp2: limit XDP frame size to the RX buffer

[Til Kaiser <mail@tk154.de>]

mvpp2 has short and long BM pools, and short pool buffers can be smaller
than PAGE_SIZE. The XDP path nevertheless initializes every xdp_buff with
PAGE_SIZE as frame size.

XDP helpers use frame_sz to validate tail growth and to derive the hard
end of the data area. Advertising PAGE_SIZE for short buffers can let
bpf_xdp_adjust_tail() grow a packet past the real allocation, corrupting
memory or later tripping skb tailroom checks.

Initialize the XDP buffer with bm_pool->frag_size so XDP tailroom matches
the actual buffer backing the packet.

Fixes: 07dd0a7aae7f ("mvpp2: add basic XDP support")
Signed-off-by: Til Kaiser <mail@tk154.de>
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 92a701f4fe3f..3372ed27cc8d 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -3979,7 +3979,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
 			else
 				xdp_rxq = &rxq->xdp_rxq_long;
 
-			xdp_init_buff(&xdp, PAGE_SIZE, xdp_rxq);
+			xdp_init_buff(&xdp, bm_pool->frag_size, xdp_rxq);
 			xdp_prepare_buff(&xdp, data,
 					 MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM,
 					 rx_bytes, true);
-- 
2.54.0