Subject: [PATCH 05/12] net: usb: lan78xx: limit size of local TSO packets

From: Eric Dumazet <[email-masked]>
Date: Mon, 13 Jan 2020 09:27:11 -0800

[ Upstream commit f8d7408a4d7f60f8b2df0f81decdc882dd9c20dc ]

lan78xx_tx_bh() makes sure to not exceed MAX_SINGLE_PACKET_SIZE
bytes in the aggregated packets it builds, but does
nothing to prevent large GSO packets being submitted.

Pierre-Francois reported various hangs when/if TSO is enabled.

For localy generated packets, we can use netif_set_gso_max_size()
to limit the size of TSO packets.

Note that forwarded packets could still hit the issue,
so a complete fix might require implementing .ndo_features_check
for this driver, forcing a software segmentation if the size
of the TSO packet exceeds MAX_SINGLE_PACKET_SIZE.

Fixes: 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet device driver")
Signed-off-by: Eric Dumazet <[email-masked]>
Reported-by: RENARD Pierre-Francois <[email-masked]>
Tested-by: RENARD Pierre-Francois <[email-masked]>
Cc: Stefan Wahren <[email-masked]>
Cc: Woojung Huh <[email-masked]>
Cc: Microchip Linux Driver Support <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/usb/lan78xx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 42715520c070..7d708aeb4576 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3769,6 +3769,7 @@ static int lan78xx_probe(struct usb_interface *intf,
 
 	/* MTU range: 68 - 9000 */
 	netdev->max_mtu = MAX_SINGLE_PACKET_SIZE;
+	netif_set_gso_max_size(netdev, MAX_SINGLE_PACKET_SIZE - MAX_HEADER);
 
 	dev->ep_blkin = (intf->cur_altsetting)->endpoint + 0;
 	dev->ep_blkout = (intf->cur_altsetting)->endpoint + 1;
-- 
2.21.1