From: Sven Eckelmann <[email protected]> Before batman-adv is allowed to write to an skb, it either has to have its own copy of the skb or use skb_cow() to ensure that the data part is not shared. But batadv_frag_skb_fwd() modifies the TTL even when it is shared.
Adding a skb_cow() right before this operation avoids this and can at the same time prepare it for the modifications required to forward the fragment. Cc: [email protected] Fixes: 610bfc6bc99b ("batman-adv: Receive fragmented packets and merge") Signed-off-by: Sven Eckelmann <[email protected]> Signed-off-by: Simon Wunderlich <[email protected]> --- net/batman-adv/fragmentation.c | 15 ++++++++++++++- net/batman-adv/fragmentation.h | 3 ++- net/batman-adv/routing.c | 3 +-- 3 files changed, 17 insertions(+), 4 deletions(-) diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c index 1e42cf99f8b33..f311a42203d2e 100644 --- a/net/batman-adv/fragmentation.c +++ b/net/batman-adv/fragmentation.c @@ -386,6 +386,8 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb, * @skb: skb to forward * @recv_if: interface that the skb is received on * @orig_node_src: originator that the skb is received from + * @rx_result: set to NET_RX_SUCCESS when the fragment was forwarded and + * NET_RX_DROP when it was dropped; only valid when true is returned * * Look up the next-hop of the fragments payload and check if the merged packet * will exceed the MTU towards the next-hop. If so, the fragment is forwarded @@ -395,7 +397,8 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb, */ bool batadv_frag_skb_fwd(struct sk_buff *skb, struct batadv_hard_iface *recv_if, - struct batadv_orig_node *orig_node_src) + struct batadv_orig_node *orig_node_src, + int *rx_result) { struct batadv_priv *bat_priv = netdev_priv(recv_if->mesh_iface); struct batadv_neigh_node *neigh_node = NULL; @@ -414,12 +417,22 @@ bool batadv_frag_skb_fwd(struct sk_buff *skb, */ total_size = ntohs(packet->total_size); if (total_size > neigh_node->if_incoming->net_dev->mtu) { + if (skb_cow(skb, ETH_HLEN) < 0) { + kfree_skb(skb); + *rx_result = NET_RX_DROP; + ret = true; + goto out; + } + + packet = (struct batadv_frag_packet *)skb->data; + batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_FWD); batadv_add_counter(bat_priv, BATADV_CNT_FRAG_FWD_BYTES, skb->len + ETH_HLEN); packet->ttl--; batadv_send_unicast_skb(skb, neigh_node); + *rx_result = NET_RX_SUCCESS; ret = true; } diff --git a/net/batman-adv/fragmentation.h b/net/batman-adv/fragmentation.h index dbf0871f87030..51e281027ab63 100644 --- a/net/batman-adv/fragmentation.h +++ b/net/batman-adv/fragmentation.h @@ -19,7 +19,8 @@ void batadv_frag_purge_orig(struct batadv_orig_node *orig, bool (*check_cb)(struct batadv_frag_table_entry *)); bool batadv_frag_skb_fwd(struct sk_buff *skb, struct batadv_hard_iface *recv_if, - struct batadv_orig_node *orig_node_src); + struct batadv_orig_node *orig_node_src, + int *rx_result); bool batadv_frag_skb_buffer(struct sk_buff **skb, struct batadv_orig_node *orig_node); int batadv_frag_send_packet(struct sk_buff *skb, diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c index 8786b66c8a924..9db57fd36e7d4 100644 --- a/net/batman-adv/routing.c +++ b/net/batman-adv/routing.c @@ -1168,10 +1168,9 @@ int batadv_recv_frag_packet(struct sk_buff *skb, /* Route the fragment if it is not for us and too big to be merged. */ if (!batadv_is_my_mac(bat_priv, frag_packet->dest) && - batadv_frag_skb_fwd(skb, recv_if, orig_node_src)) { + batadv_frag_skb_fwd(skb, recv_if, orig_node_src, &ret)) { /* skb was consumed */ skb = NULL; - ret = NET_RX_SUCCESS; goto put_orig_node; } -- 2.47.3
