[PATCH 6.1 173/473] net: usb: smsc95xx: stop lying about skb->truesize

Greg Kroah-Hartman
2024-06-06T14:14:58Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d50729f1d60bca822ef6d9c1a5fb28d486bd7593 ]

Some usb drivers try to set small skb->truesize and break
core networking stacks.

In this patch, I removed one of the skb->truesize override.

I also replaced one skb_clone() by an allocation of a fresh
and small skb, to get minimally sized skbs, like we did
in commit 1e2c61172342 ("net: cdc_ncm: reduce skb truesize
in rx path") and 4ce62d5b2f7a ("net: usb: ax88179_178a:
stop lying about skb->truesize")

v3: also fix a sparse error ( https://lore.kernel.org/oe-kbuild-all/202405091310.KvncIecx-lkp@intel.com/ )
v2: leave the skb_trim() game because smsc95xx_rx_csum_offload()
needs the csum part. (Jakub)
While we are it, use get_unaligned() in smsc95xx_rx_csum_offload().

Fixes: 2f7ca802bdae ("net: Add SMSC LAN9500 USB2.0 10/100 ethernet adapter driver")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Steve Glendinning <steve.glendinning@shawell.net>
Cc: UNGLinuxDriver@microchip.com
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240509083313.2113832-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/usb/smsc95xx.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 2fa46baa589e5..cbea246664795 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1810,9 +1810,11 @@ static int smsc95xx_reset_resume(struct usb_interface *intf)

static void smsc95xx_rx_csum_offload(struct sk_buff *skb)
{
- skb->csum = *(u16 *)(skb_tail_pointer(skb) - 2);
+ u16 *csum_ptr = (u16 *)(skb_tail_pointer(skb) - 2);
+
+ skb->csum = (__force __wsum)get_unaligned(csum_ptr);
skb->ip_summed = CHECKSUM_COMPLETE;
- skb_trim(skb, skb->len - 2);
+ skb_trim(skb, skb->len - 2); /* remove csum */
}

static int smsc95xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
@@ -1870,25 +1872,22 @@ static int smsc95xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
if (dev->net->features & NETIF_F_RXCSUM)
smsc95xx_rx_csum_offload(skb);
skb_trim(skb, skb->len - 4); /* remove fcs */
- skb->truesize = size + sizeof(struct sk_buff);

return 1;
}

- ax_skb = skb_clone(skb, GFP_ATOMIC);
+ ax_skb = netdev_alloc_skb_ip_align(dev->net, size);
if (unlikely(!ax_skb)) {
netdev_warn(dev->net, "Error allocating skb\n");
return 0;
}

- ax_skb->len = size;
- ax_skb->data = packet;
- skb_set_tail_pointer(ax_skb, size);
+ skb_put(ax_skb, size);
+ memcpy(ax_skb->data, packet, size);

if (dev->net->features & NETIF_F_RXCSUM)
smsc95xx_rx_csum_offload(ax_skb);
skb_trim(ax_skb, ax_skb->len - 4); /* remove fcs */
- ax_skb->truesize = size + sizeof(struct sk_buff);

usbnet_skb_return(dev, ax_skb);
}
--
2.43.0