Patch "net: bridge: fix corrupted ethernet header on multicast-to-unicast" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    net: bridge: fix corrupted ethernet header on multicast-to-unicast

to the 5.15-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-bridge-fix-corrupted-ethernet-header-on-multicas.patch
and it can be found in the queue-5.15 subdirectory.

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



commit 305ba1b17cebad08cf1635d0b9e624489f477e59
Author: Felix Fietkau <nbd@xxxxxxxx>
Date:   Sun May 5 20:42:38 2024 +0200

    net: bridge: fix corrupted ethernet header on multicast-to-unicast
    
    [ Upstream commit 86b29d830ad69eecff25b22dc96c14c6573718e6 ]
    
    The change from skb_copy to pskb_copy unfortunately changed the data
    copying to omit the ethernet header, since it was pulled before reaching
    this point. Fix this by calling __skb_push/pull around pskb_copy.
    
    Fixes: 59c878cbcdd8 ("net: bridge: fix multicast-to-unicast with fraglist GSO")
    Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
    Acked-by: Nikolay Aleksandrov <razor@xxxxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 0bdd2892646db..1b66c276118a3 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -253,6 +253,7 @@ static void maybe_deliver_addr(struct net_bridge_port *p, struct sk_buff *skb,
 {
 	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
 	const unsigned char *src = eth_hdr(skb)->h_source;
+	struct sk_buff *nskb;
 
 	if (!should_deliver(p, skb))
 		return;
@@ -261,12 +262,16 @@ static void maybe_deliver_addr(struct net_bridge_port *p, struct sk_buff *skb,
 	if (skb->dev == p->dev && ether_addr_equal(src, addr))
 		return;
 
-	skb = pskb_copy(skb, GFP_ATOMIC);
-	if (!skb) {
+	__skb_push(skb, ETH_HLEN);
+	nskb = pskb_copy(skb, GFP_ATOMIC);
+	__skb_pull(skb, ETH_HLEN);
+	if (!nskb) {
 		DEV_STATS_INC(dev, tx_dropped);
 		return;
 	}
 
+	skb = nskb;
+	__skb_pull(skb, ETH_HLEN);
 	if (!is_broadcast_ether_addr(addr))
 		memcpy(eth_hdr(skb)->h_dest, addr, ETH_ALEN);