Patch "net: usb: smsc95xx: stop lying about skb->truesize" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: usb: smsc95xx: stop lying about skb->truesize

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-usb-smsc95xx-stop-lying-about-skb-truesize.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit af5e46f3da21616414bc839268d5066f6c8f52ef
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Thu May 9 08:33:13 2024 +0000

    net: usb: smsc95xx: stop lying about skb->truesize
    
    [ 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@xxxxxxxxx/ )
    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@xxxxxxxxxx>
    Cc: Steve Glendinning <steve.glendinning@xxxxxxxxxxx>
    Cc: UNGLinuxDriver@xxxxxxxxxxxxx
    Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240509083313.2113832-1-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 37547ac72840f..be5543c71d069 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1924,9 +1924,11 @@ 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)
@@ -1985,25 +1987,22 @@ 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);
 		}