From 48067b2ae4504500a7093d9e1e16b42e70330480 Mon Sep 17 00:00:00 2001 From: Sven Eckelmann Date: Sun, 28 Jun 2026 08:45:41 +0200 Subject: [PATCH] batman-adv: dat: acquire ARP hw source only after skb realloc The pskb_may_pull() called by batadv_get_vid() 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. Cc: stable@vger.kernel.org Fixes: b61ec31c8575 ("batman-adv: Snoop DHCPACKs for DAT") Signed-off-by: Sven Eckelmann --- net/batman-adv/distributed-arp-table.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c index ae39ceaa2e29a..ead02c9e08484 100644 --- a/net/batman-adv/distributed-arp-table.c +++ b/net/batman-adv/distributed-arp-table.c @@ -1747,6 +1747,7 @@ void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv, struct ethhdr *ethhdr; __be32 ip_src, yiaddr; unsigned short vid; + int hdr_size_tmp; __be16 proto; u8 *hw_src; @@ -1763,8 +1764,10 @@ void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv, if (!batadv_dat_check_dhcp_ack(skb, proto, &ip_src, chaddr, &yiaddr)) return; + hdr_size_tmp = hdr_size; + vid = batadv_dat_get_vid(skb, &hdr_size_tmp); + ethhdr = (struct ethhdr *)(skb->data + hdr_size); hw_src = ethhdr->h_source; - vid = batadv_dat_get_vid(skb, &hdr_size); batadv_dat_entry_add(bat_priv, yiaddr, chaddr, vid); batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid); -- 2.47.3