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batman-adv: mcast: ensure unshared skb for multicast packets

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When a packet is transmitted via a batman-adv interface and has already
enough room for the header then nothing will make sure that the skbuff is
unshared. But it is not allowed to modify a currently shared skbuff.

Always make sure that the pskb_expand_head() is not only called for a too
small header but also for shared skbuffs.

Cc: stable@vger.kernel.org
Fixes: 9003913322 ("batman-adv: mcast: implement multicast packet generation")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
This commit is contained in:
Sven Eckelmann 2026-07-09 21:17:08 +02:00
parent 7aedb59b80
commit 82bf207f48
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GPG Key ID: 4D0F772BD314F5CB
1 changed files with 1 additions and 2 deletions
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3
net/batman-adv/multicast_forw.c
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@ -1105,8 +1105,7 @@ static int batadv_mcast_forw_expand_head(struct batadv_priv *bat_priv,
return -EINVAL;
}
if (skb_headroom(skb) < hdr_size &&
pskb_expand_head(skb, hdr_size, 0, GFP_ATOMIC) < 0)
if (skb_cow(skb, hdr_size) < 0)
return -ENOMEM;
return 0;