From 23c110c4cdbce17b6c5df90298168fc4b990ecc1 Mon Sep 17 00:00:00 2001 From: Sabrina Dubroca Date: Thu, 20 Oct 2016 15:58:02 +0200 Subject: [PATCH] net: add recursion limit to GRO MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit [ Upstream commit fcd91dd449867c6bfe56a81cabba76b829fd05cd ] Currently, GRO can do unlimited recursion through the gro_receive handlers. This was fixed for tunneling protocols by limiting tunnel GRO to one level with encap_mark, but both VLAN and TEB still have this problem. Thus, the kernel is vulnerable to a stack overflow, if we receive a packet composed entirely of VLAN headers. This patch adds a recursion counter to the GRO layer to prevent stack overflow. When a gro_receive function hits the recursion limit, GRO is aborted for this skb and it is processed normally. This recursion counter is put in the GRO CB, but could be turned into a percpu counter if we run out of space in the CB. Thanks to Vladimír Beneš for the initial bug report. Fixes: CVE-2016-7039 Fixes: 9b174d88c257 ("net: Add Transparent Ethernet Bridging GRO support.") Fixes: 66e5133f19e9 ("vlan: Add GRO support for non hardware accelerated vlan") Signed-off-by: Sabrina Dubroca Reviewed-by: Jiri Benc Acked-by: Hannes Frederic Sowa Acked-by: Tom Herbert Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/geneve.c | 2 +- drivers/net/vxlan.c | 2 +- include/linux/netdevice.h | 39 ++++++++++++++++++++++++++++++++++++++- net/8021q/vlan.c | 2 +- net/core/dev.c | 1 + net/ethernet/eth.c | 2 +- net/ipv4/af_inet.c | 2 +- net/ipv4/fou.c | 4 ++-- net/ipv4/gre_offload.c | 2 +- net/ipv4/udp_offload.c | 2 +- net/ipv6/ip6_offload.c | 2 +- 11 files changed, 49 insertions(+), 11 deletions(-) diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c index 3c20e87bb7619..16af1ce99233a 100644 --- a/drivers/net/geneve.c +++ b/drivers/net/geneve.c @@ -453,7 +453,7 @@ static struct sk_buff **geneve_gro_receive(struct sock *sk, skb_gro_pull(skb, gh_len); skb_gro_postpull_rcsum(skb, gh, gh_len); - pp = ptype->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb); flush = 0; out_unlock: diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c index 6e65832051d6d..5ae664c025287 100644 --- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -584,7 +584,7 @@ static struct sk_buff **vxlan_gro_receive(struct sock *sk, } } - pp = eth_gro_receive(head, skb); + pp = call_gro_receive(eth_gro_receive, head, skb); flush = 0; out: diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index ae4b275f42c3b..e942c67ea2300 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2154,7 +2154,10 @@ struct napi_gro_cb { /* Used to determine if flush_id can be ignored */ u8 is_atomic:1; - /* 5 bit hole */ + /* Number of gro_receive callbacks this packet already went through */ + u8 recursion_counter:4; + + /* 1 bit hole */ /* used to support CHECKSUM_COMPLETE for tunneling protocols */ __wsum csum; @@ -2165,6 +2168,40 @@ struct napi_gro_cb { #define NAPI_GRO_CB(skb) ((struct napi_gro_cb *)(skb)->cb) +#define GRO_RECURSION_LIMIT 15 +static inline int gro_recursion_inc_test(struct sk_buff *skb) +{ + return ++NAPI_GRO_CB(skb)->recursion_counter == GRO_RECURSION_LIMIT; +} + +typedef struct sk_buff **(*gro_receive_t)(struct sk_buff **, struct sk_buff *); +static inline struct sk_buff **call_gro_receive(gro_receive_t cb, + struct sk_buff **head, + struct sk_buff *skb) +{ + if (unlikely(gro_recursion_inc_test(skb))) { + NAPI_GRO_CB(skb)->flush |= 1; + return NULL; + } + + return cb(head, skb); +} + +typedef struct sk_buff **(*gro_receive_sk_t)(struct sock *, struct sk_buff **, + struct sk_buff *); +static inline struct sk_buff **call_gro_receive_sk(gro_receive_sk_t cb, + struct sock *sk, + struct sk_buff **head, + struct sk_buff *skb) +{ + if (unlikely(gro_recursion_inc_test(skb))) { + NAPI_GRO_CB(skb)->flush |= 1; + return NULL; + } + + return cb(sk, head, skb); +} + struct packet_type { __be16 type; /* This is really htons(ether_type). */ struct net_device *dev; /* NULL is wildcarded here */ diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c index 8de138d3306bd..f2531ad66b68b 100644 --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -664,7 +664,7 @@ static struct sk_buff **vlan_gro_receive(struct sk_buff **head, skb_gro_pull(skb, sizeof(*vhdr)); skb_gro_postpull_rcsum(skb, vhdr, sizeof(*vhdr)); - pp = ptype->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb); out_unlock: rcu_read_unlock(); diff --git a/net/core/dev.c b/net/core/dev.c index 746bf31659ec3..fc63c6d8a1b28 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4496,6 +4496,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff NAPI_GRO_CB(skb)->flush = 0; NAPI_GRO_CB(skb)->free = 0; NAPI_GRO_CB(skb)->encap_mark = 0; + NAPI_GRO_CB(skb)->recursion_counter = 0; NAPI_GRO_CB(skb)->is_fou = 0; NAPI_GRO_CB(skb)->is_atomic = 1; NAPI_GRO_CB(skb)->gro_remcsum_start = 0; diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c index 66dff5e3d7728..02acfff36028b 100644 --- a/net/ethernet/eth.c +++ b/net/ethernet/eth.c @@ -439,7 +439,7 @@ struct sk_buff **eth_gro_receive(struct sk_buff **head, skb_gro_pull(skb, sizeof(*eh)); skb_gro_postpull_rcsum(skb, eh, sizeof(*eh)); - pp = ptype->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb); out_unlock: rcu_read_unlock(); diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 55513e654d799..eebbc0f2baa8d 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1388,7 +1388,7 @@ struct sk_buff **inet_gro_receive(struct sk_buff **head, struct sk_buff *skb) skb_gro_pull(skb, sizeof(*iph)); skb_set_transport_header(skb, skb_gro_offset(skb)); - pp = ops->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ops->callbacks.gro_receive, head, skb); out_unlock: rcu_read_unlock(); diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c index 321d57f825ce0..5351b61ab8d3d 100644 --- a/net/ipv4/fou.c +++ b/net/ipv4/fou.c @@ -249,7 +249,7 @@ static struct sk_buff **fou_gro_receive(struct sock *sk, if (!ops || !ops->callbacks.gro_receive) goto out_unlock; - pp = ops->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ops->callbacks.gro_receive, head, skb); out_unlock: rcu_read_unlock(); @@ -441,7 +441,7 @@ next_proto: if (WARN_ON_ONCE(!ops || !ops->callbacks.gro_receive)) goto out_unlock; - pp = ops->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ops->callbacks.gro_receive, head, skb); flush = 0; out_unlock: diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c index ecd1e09dbbf13..6871f59cd0c09 100644 --- a/net/ipv4/gre_offload.c +++ b/net/ipv4/gre_offload.c @@ -227,7 +227,7 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head, /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/ skb_gro_postpull_rcsum(skb, greh, grehlen); - pp = ptype->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb); flush = 0; out_unlock: diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index 81f253b6ff363..6de9f977356e5 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -293,7 +293,7 @@ unflush: skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */ skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr)); - pp = udp_sk(sk)->gro_receive(sk, head, skb); + pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb); out_unlock: rcu_read_unlock(); diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c index 22e90e56b5a9f..a09418bda1f8b 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -243,7 +243,7 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head, skb_gro_postpull_rcsum(skb, iph, nlen); - pp = ops->callbacks.gro_receive(head, skb); + pp = call_gro_receive(ops->callbacks.gro_receive, head, skb); out_unlock: rcu_read_unlock(); -- 2.47.2