The caller of ndo_start_xmit may not already have called skb_reset_mac_header. The returned value of skb_mac_header/eth_hdr therefore can be in the wrong position and even outside the current skbuff. This for example happens when the user binds to the device using a PF_PACKET-SOCK_RAW with enabled qdisc-bypass:

int opt = 4; setsockopt(sock, SOL_PACKET, PACKET_QDISC_BYPASS, &opt, sizeof(opt));

Since eth_hdr is used all over the codebase, the batadv_interface_tx function must always take care of resetting it.

Fixes: fe28a94c01e1 ("batman-adv: receive packets directly using skbs") Reported-by: syzbot+9d7405c7faa390e60b4e@syzkaller.appspotmail.com Reported-by: syzbot+7d20bc3f1ddddc0f9079@syzkaller.appspotmail.com Signed-off-by: Sven Eckelmann sven@narfation.org --- Cc: syzkaller-bugs@googlegroups.com --- net/batman-adv/soft-interface.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index 5db5a0a4..b85ca809 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -221,6 +221,8 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,

netif_trans_update(soft_iface); vid = batadv_get_vid(skb, 0); + + skb_reset_mac_header(skb); ethhdr = eth_hdr(skb);

switch (ntohs(ethhdr->h_proto)) {