| From 82bf207f48ebb7a38157f1d91dac884fc9b8cfd8 Mon Sep 17 00:00:00 2001 |
| From: Sven Eckelmann <sven@narfation.org> |
| Date: Thu, 9 Jul 2026 21:17:08 +0200 |
| Subject: batman-adv: mcast: ensure unshared skb for multicast packets |
| |
| From: Sven Eckelmann <sven@narfation.org> |
| |
| commit 82bf207f48ebb7a38157f1d91dac884fc9b8cfd8 upstream. |
| |
| 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: 90039133221e ("batman-adv: mcast: implement multicast packet generation") |
| Signed-off-by: Sven Eckelmann <sven@narfation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/batman-adv/multicast_forw.c | 3 +-- |
| 1 file changed, 1 insertion(+), 2 deletions(-) |
| |
| --- a/net/batman-adv/multicast_forw.c |
| +++ b/net/batman-adv/multicast_forw.c |
| @@ -1100,8 +1100,7 @@ static int batadv_mcast_forw_expand_head |
| 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; |
