FAILED: patch "[PATCH] batman-adv: retrieve ethhdr after potential skb realloc on RX" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 035e1fed892d3d06002a73ff73668f618a514644
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026072057-food-spender-efd0@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 035e1fed892d3d06002a73ff73668f618a514644 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <sven@narfation.org>
Date: Sun, 28 Jun 2026 06:44:13 +0200
Subject: [PATCH] batman-adv: retrieve ethhdr after potential skb realloc on RX

pskb_may_pull() in batadv_interface_rx() could reallocate the buffer behind
the skb. Variables which were pointing to the old buffer need to be
reassigned to avoid an use-after-free.

This was done correctly for the VLAN header but missed for the ethernet
header which is later used for the TT and AP isolation handling.

Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol")
Fixes: c78296665c3d ("batman-adv: Check skb size before using encapsulated ETH+VLAN header")
Signed-off-by: Sven Eckelmann <sven@narfation.org>

diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c
index 44026810b99c..511f70e0706a 100644
--- a/net/batman-adv/mesh-interface.c
+++ b/net/batman-adv/mesh-interface.c
@@ -434,6 +434,7 @@ void batadv_interface_rx(struct net_device *mesh_iface,
 		if (!pskb_may_pull(skb, VLAN_ETH_HLEN))
 			goto dropped;
 
+		ethhdr = eth_hdr(skb);
 		vhdr = skb_vlan_eth_hdr(skb);
 
 		/* drop batman-in-batman packets to prevent loops */