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batman-adv: ensure minimal ethernet header on TX

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As documented in commit 8bd67ebb50 ("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.

Cc: stable@vger.kernel.org
Fixes: c6c8fea297 ("net: Add batman-adv meshing protocol")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
This commit is contained in:
Sven Eckelmann 2026-07-02 11:46:21 +02:00
parent 26560c4a03
commit 49df66b799
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1 changed files with 3 additions and 0 deletions
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3
net/batman-adv/mesh-interface.c
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@ -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));