[PATCH 4.9 86/97] net: usb: lan78xx: limit size of local TSO packets

[Greg Kroah-Hartman]

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ 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 <edumazet@xxxxxxxxxx>
Reported-by: RENARD Pierre-Francois <pfrenard@xxxxxxxxx>
Tested-by: RENARD Pierre-Francois <pfrenard@xxxxxxxxx>
Cc: Stefan Wahren <stefan.wahren@xxxxxxxx>
Cc: Woojung Huh <woojung.huh@xxxxxxxxxxxxx>
Cc: Microchip Linux Driver Support <UNGLinuxDriver@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/usb/lan78xx.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3375,6 +3375,7 @@ static int lan78xx_probe(struct usb_inte
 
 	if (netdev->mtu > (dev->hard_mtu - netdev->hard_header_len))
 		netdev->mtu = dev->hard_mtu - netdev->hard_header_len;
+	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;