net: usb: ax88179_178a: stop lying about skb->truesize

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

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

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 1e2c611 ("net: cdc_ncm: reduce skb truesize
in rx path")

Fixes: f8ebb3a ("net: usb: ax88179_178a: Fix packet receiving")
Reported-by: shironeko <shironeko@tesaguri.club>
Closes: https://lore.kernel.org/netdev/c110f41a0d2776b525930f213ca9715c@tesaguri.club/
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jose Alonso <joalonsof@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240421193828.1966195-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/ax88179_178a.c

@@ -1456,21 +1456,16 @@ static int ax88179_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 			/* Skip IP alignment pseudo header */
 			skb_pull(skb, 2);
 
-			skb->truesize = SKB_TRUESIZE(pkt_len_plus_padd);
 			ax88179_rx_checksum(skb, pkt_hdr);
 			return 1;
 		}
 
-		ax_skb = skb_clone(skb, GFP_ATOMIC);
+		ax_skb = netdev_alloc_skb_ip_align(dev->net, pkt_len);
 		if (!ax_skb)
 			return 0;
-		skb_trim(ax_skb, pkt_len);
+		skb_put(ax_skb, pkt_len);
+		memcpy(ax_skb->data, skb->data + 2, pkt_len);
 
-		/* Skip IP alignment pseudo header */
-		skb_pull(ax_skb, 2);
-
-		skb->truesize = pkt_len_plus_padd +
-				SKB_DATA_ALIGN(sizeof(struct sk_buff));
 		ax88179_rx_checksum(ax_skb, pkt_hdr);
 		usbnet_skb_return(dev, ax_skb);