From c98c3e521913b8dd5fee4d3b90dc9ed7a47e5bee Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Linus=20L=C3=BCssing?= Date: Tue, 6 Aug 2013 20:21:15 +0200 Subject: [PATCH] batman-adv: fix potential kernel paging errors for unicast transmissions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There are several functions which might reallocate skb data. Currently some places keep reusing their old ethhdr pointer regardless of whether they became invalid after such a reallocation or not. This potentially leads to kernel paging errors. This patch fixes these by refetching the ethdr pointer after the potential reallocations. Signed-off-by: Linus Lüssing Signed-off-by: Marek Lindner --- bridge_loop_avoidance.c | 2 ++ gateway_client.c | 13 ++++++++++++- gateway_client.h | 3 +-- soft-interface.c | 9 ++++++++- unicast.c | 13 ++++++++++--- 5 files changed, 33 insertions(+), 7 deletions(-) diff --git a/bridge_loop_avoidance.c b/bridge_loop_avoidance.c index e14531f..264de88 100644 --- a/bridge_loop_avoidance.c +++ b/bridge_loop_avoidance.c @@ -1529,6 +1529,8 @@ out: * in these cases, the skb is further handled by this function and * returns 1, otherwise it returns 0 and the caller shall further * process the skb. + * + * This call might reallocate skb data. */ int batadv_bla_tx(struct batadv_priv *bat_priv, struct sk_buff *skb, unsigned short vid) diff --git a/gateway_client.c b/gateway_client.c index f105219..7614af3 100644 --- a/gateway_client.c +++ b/gateway_client.c @@ -508,6 +508,7 @@ out: return 0; } +/* this call might reallocate skb data */ static bool batadv_is_type_dhcprequest(struct sk_buff *skb, int header_len) { int ret = false; @@ -568,6 +569,7 @@ out: return ret; } +/* this call might reallocate skb data */ bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len) { struct ethhdr *ethhdr; @@ -619,6 +621,12 @@ bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len) if (!pskb_may_pull(skb, *header_len + sizeof(*udphdr))) return false; + + /* skb->data might have been reallocated by pskb_may_pull() */ + ethhdr = (struct ethhdr *)skb->data; + if (ntohs(ethhdr->h_proto) == ETH_P_8021Q) + ethhdr = (struct ethhdr *)(skb->data + VLAN_HLEN); + udphdr = (struct udphdr *)(skb->data + *header_len); *header_len += sizeof(*udphdr); @@ -634,12 +642,14 @@ bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len) return true; } +/* this call might reallocate skb data */ bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, - struct sk_buff *skb, struct ethhdr *ethhdr) + struct sk_buff *skb) { struct batadv_neigh_node *neigh_curr = NULL, *neigh_old = NULL; struct batadv_orig_node *orig_dst_node = NULL; struct batadv_gw_node *curr_gw = NULL; + struct ethhdr *ethhdr; bool ret, out_of_range = false; unsigned int header_len = 0; uint8_t curr_tq_avg; @@ -648,6 +658,7 @@ bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, if (!ret) goto out; + ethhdr = (struct ethhdr *)skb->data; orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source, ethhdr->h_dest); if (!orig_dst_node) diff --git a/gateway_client.h b/gateway_client.h index 039902d..1037d75 100644 --- a/gateway_client.h +++ b/gateway_client.h @@ -34,7 +34,6 @@ void batadv_gw_node_delete(struct batadv_priv *bat_priv, void batadv_gw_node_purge(struct batadv_priv *bat_priv); int batadv_gw_client_seq_print_text(struct seq_file *seq, void *offset); bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len); -bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, - struct sk_buff *skb, struct ethhdr *ethhdr); +bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, struct sk_buff *skb); #endif /* _NET_BATMAN_ADV_GATEWAY_CLIENT_H_ */ diff --git a/soft-interface.c b/soft-interface.c index 700d0b4..0f04e1c 100644 --- a/soft-interface.c +++ b/soft-interface.c @@ -180,6 +180,9 @@ static int batadv_interface_tx(struct sk_buff *skb, if (batadv_bla_tx(bat_priv, skb, vid)) goto dropped; + /* skb->data might have been reallocated by batadv_bla_tx() */ + ethhdr = (struct ethhdr *)skb->data; + /* Register the client MAC in the transtable */ if (!is_multicast_ether_addr(ethhdr->h_source)) batadv_tt_local_add(soft_iface, ethhdr->h_source, skb->skb_iif); @@ -220,6 +223,10 @@ static int batadv_interface_tx(struct sk_buff *skb, default: break; } + + /* reminder: ethhdr might have become unusable from here on + * (batadv_gw_is_dhcp_target() might have reallocated skb data) + */ } /* ethernet packet should be broadcasted */ @@ -266,7 +273,7 @@ static int batadv_interface_tx(struct sk_buff *skb, /* unicast packet */ } else { if (atomic_read(&bat_priv->gw_mode) != BATADV_GW_MODE_OFF) { - ret = batadv_gw_out_of_range(bat_priv, skb, ethhdr); + ret = batadv_gw_out_of_range(bat_priv, skb); if (ret) goto dropped; } diff --git a/unicast.c b/unicast.c index dc8b5d4..688a041 100644 --- a/unicast.c +++ b/unicast.c @@ -326,7 +326,9 @@ static bool batadv_unicast_push_and_fill_skb(struct sk_buff *skb, int hdr_size, * @skb: the skb containing the payload to encapsulate * @orig_node: the destination node * - * Returns false if the payload could not be encapsulated or true otherwise + * Returns false if the payload could not be encapsulated or true otherwise. + * + * This call might reallocate skb data. */ static bool batadv_unicast_prepare_skb(struct sk_buff *skb, struct batadv_orig_node *orig_node) @@ -343,7 +345,9 @@ static bool batadv_unicast_prepare_skb(struct sk_buff *skb, * @orig_node: the destination node * @packet_subtype: the batman 4addr packet subtype to use * - * Returns false if the payload could not be encapsulated or true otherwise + * Returns false if the payload could not be encapsulated or true otherwise. + * + * This call might reallocate skb data. */ bool batadv_unicast_4addr_prepare_skb(struct batadv_priv *bat_priv, struct sk_buff *skb, @@ -401,7 +405,7 @@ int batadv_unicast_generic_send_skb(struct batadv_priv *bat_priv, struct batadv_neigh_node *neigh_node; int data_len = skb->len; int ret = NET_RX_DROP; - unsigned int dev_mtu; + unsigned int dev_mtu, header_len; /* get routing information */ if (is_multicast_ether_addr(ethhdr->h_dest)) { @@ -429,10 +433,12 @@ find_router: switch (packet_type) { case BATADV_UNICAST: batadv_unicast_prepare_skb(skb, orig_node); + header_len = sizeof(struct batadv_unicast_packet); break; case BATADV_UNICAST_4ADDR: batadv_unicast_4addr_prepare_skb(bat_priv, skb, orig_node, packet_subtype); + header_len = sizeof(struct batadv_unicast_4addr_packet); break; default: /* this function supports UNICAST and UNICAST_4ADDR only. It @@ -441,6 +447,7 @@ find_router: goto out; } + ethhdr = (struct ethhdr *)(skb->data + header_len); unicast_packet = (struct batadv_unicast_packet *)skb->data; /* inform the destination node that we are still missing a correct route -- 1.7.10.4