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batman-adv: mcast: linearize skbuff for packet generation

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batadv_mcast_forw_packet() and batadv_mcast_forw_scrape() is not only
called (indirectly) by the unsharing+linearizing batadv_recv_mcast_packet()
handler. When it is called (indirectly) by batadv_mcast_forw_mcsend() then
it will be unshared but not linearized. The SKB_LINEAR_ASSERT() can
therefore cause a fatal BUG().

The linearization should happen during the expansion of the head because
the scrape function can be hit already during the initial
batadv_mcast_forw_mode() selection code:

* batadv_interface_tx
* batadv_mcast_forw_mode
* batadv_mcast_forw_mode_by_count()
* batadv_mcast_forw_push()
  -> calls batadv_mcast_forw_expand_head() before everything else
* batadv_mcast_forw_push_tvlvs()
* batadv_mcast_forw_push_dests()
* batadv_mcast_forw_push_adjust_padding()
* batadv_mcast_forw_scrape()

Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@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 21:26:13 +02:00
parent 82bf207f48
commit 6a30a59e26
No known key found for this signature in database
GPG Key ID: 4D0F772BD314F5CB
1 changed files with 4 additions and 0 deletions
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4
net/batman-adv/multicast_forw.c
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@ -1108,6 +1108,10 @@ static int batadv_mcast_forw_expand_head(struct batadv_priv *bat_priv,
if (skb_cow(skb, hdr_size) < 0)
return -ENOMEM;
/* batadv_mcast_forw_scrape() + batadv_mcast_forw_packet() require linearized skb */
if (skb_linearize(skb) < 0)
return -ENOMEM;
return 0;
}