FAILED: patch "[PATCH] batman-adv: ensure minimal ethernet header on TX" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-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 <[email protected]>.

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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 49df66b7993c80b80c7eb9a84ba5b3410c8296a0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072041-bruising-resort-e0fb@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 49df66b7993c80b80c7eb9a84ba5b3410c8296a0 Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <[email protected]>
Date: Thu, 2 Jul 2026 11:46:21 +0200
Subject: [PATCH] batman-adv: ensure minimal ethernet header on TX

As documented in commit 8bd67ebb50c0 ("net: bridge: xmit: make sure we have at least eth header len bytes"), it is possible by for a local user with eBPF TC hook access to attach a tc filter which truncates the packet and redirects to an batadv interface. But the code assumes that at least ETH_HLEN bytes are available and thus might read outside of the available buffer.

The batadv_interface_tx() must therefore always check itself if enough data is available for the ethernet header and don't rely on min_header_len.

index 511f70e0706a..0b75234521b6 100644
@@ -195,6 +195,9 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 	if (READ_ONCE(bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
 		goto dropped;
 
+	if (!pskb_may_pull(skb, ETH_HLEN))
+		goto dropped;
+
 	/* reset control block to avoid left overs from previous users */
 	memset(skb->cb, 0, sizeof(struct batadv_skb_cb));
 

commit 49df66b7993c80b80c7eb9a84ba5b3410c8296a0 upstream.

As documented in commit 8bd67ebb50c0 ("net: bridge: xmit: make sure we have at least eth header len bytes"), it is possible by for a local user with eBPF TC hook access to attach a tc filter which truncates the packet and redirects to an batadv interface. But the code assumes that at least ETH_HLEN bytes are available and thus might read outside of the available buffer.

The batadv_interface_tx() must therefore always check itself if enough data is available for the ethernet header and don't rely on min_header_len.

---
 net/batman-adv/soft-interface.c | 3 +++
 1 file changed, 3 insertions(+)

index f46064333f334..f64c3058ad191 100644
@@ -206,6 +206,9 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 	if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
 		goto dropped;
 
+	if (!pskb_may_pull(skb, ETH_HLEN))
+		goto dropped;
+
 	/* reset control block to avoid left overs from previous users */
 	memset(skb->cb, 0, sizeof(struct batadv_skb_cb));
 

2.47.3

Queued for 6.12, thanks.

Thanks,
Sasha