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ip: validate header length on virtual device xmit

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KMSAN detected read beyond end of buffer in vti and sit devices when
passing truncated packets with PF_PACKET. The issue affects additional
ip tunnel devices.

Extend commit 76c0ddd8c3 ("ip6_tunnel: be careful when accessing the
inner header") and commit ccfec9e5cb ("ip_tunnel: be careful when
accessing the inner header").

Move the check to a separate helper and call at the start of each
ndo_start_xmit function in net/ipv4 and net/ipv6.

Minor changes:
- convert dev_kfree_skb to kfree_skb on error path,
  as dev_kfree_skb calls consume_skb which is not for error paths.
- use pskb_network_may_pull even though that is pedantic here,
  as the same as pskb_may_pull for devices without llheaders.
- do not cache ipv6 hdrs if used only once
  (unsafe across pskb_may_pull, was more relevant to earlier patch)

Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2018-12-30 17:24:36 -05:00 committed by David S. Miller
parent 8c76e77f90
commit cb9f1b7838
9 changed files with 66 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
include/net/ip_tunnels.h
View File

@ -308,6 +308,26 @@ int ip_tunnel_encap_del_ops(const struct ip_tunnel_encap_ops *op,
int ip_tunnel_encap_setup(struct ip_tunnel *t,
struct ip_tunnel_encap *ipencap);
static inline bool pskb_inet_may_pull(struct sk_buff *skb)
{
int nhlen;
switch (skb->protocol) {
#if IS_ENABLED(CONFIG_IPV6)
case htons(ETH_P_IPV6):
nhlen = sizeof(struct ipv6hdr);
break;
#endif
case htons(ETH_P_IP):
nhlen = sizeof(struct iphdr);
break;
default:
nhlen = 0;
}
return pskb_network_may_pull(skb, nhlen);
}
static inline int ip_encap_hlen(struct ip_tunnel_encap *e)
{
const struct ip_tunnel_encap_ops *ops;

9
net/ipv4/ip_gre.c
View File

@ -676,6 +676,9 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
struct ip_tunnel *tunnel = netdev_priv(dev);
const struct iphdr *tnl_params;
if (!pskb_inet_may_pull(skb))
goto free_skb;
if (tunnel->collect_md) {
gre_fb_xmit(skb, dev, skb->protocol);
return NETDEV_TX_OK;
@ -719,6 +722,9 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
struct ip_tunnel *tunnel = netdev_priv(dev);
bool truncate = false;
if (!pskb_inet_may_pull(skb))
goto free_skb;
if (tunnel->collect_md) {
erspan_fb_xmit(skb, dev, skb->protocol);
return NETDEV_TX_OK;
@ -762,6 +768,9 @@ static netdev_tx_t gre_tap_xmit(struct sk_buff *skb,
{
struct ip_tunnel *tunnel = netdev_priv(dev);
if (!pskb_inet_may_pull(skb))
goto free_skb;
if (tunnel->collect_md) {
gre_fb_xmit(skb, dev, htons(ETH_P_TEB));
return NETDEV_TX_OK;

9
net/ipv4/ip_tunnel.c
View File

@ -627,7 +627,6 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
const struct iphdr *tnl_params, u8 protocol)
{
struct ip_tunnel *tunnel = netdev_priv(dev);
unsigned int inner_nhdr_len = 0;
const struct iphdr *inner_iph;
struct flowi4 fl4;
u8 tos, ttl;
@ -637,14 +636,6 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
__be32 dst;
bool connected;
/* ensure we can access the inner net header, for several users below */
if (skb->protocol == htons(ETH_P_IP))
inner_nhdr_len = sizeof(struct iphdr);
else if (skb->protocol == htons(ETH_P_IPV6))
inner_nhdr_len = sizeof(struct ipv6hdr);
if (unlikely(!pskb_may_pull(skb, inner_nhdr_len)))
goto tx_error;
inner_iph = (const struct iphdr *)skb_inner_network_header(skb);
connected = (tunnel->parms.iph.daddr != 0);

12
net/ipv4/ip_vti.c
View File

@ -241,6 +241,9 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
struct ip_tunnel *tunnel = netdev_priv(dev);
struct flowi fl;
if (!pskb_inet_may_pull(skb))
goto tx_err;
memset(&fl, 0, sizeof(fl));
switch (skb->protocol) {
@ -253,15 +256,18 @@ static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
break;
default:
dev->stats.tx_errors++;
dev_kfree_skb(skb);
return NETDEV_TX_OK;
goto tx_err;
}
/* override mark with tunnel output key */
fl.flowi_mark = be32_to_cpu(tunnel->parms.o_key);
return vti_xmit(skb, dev, &fl);
tx_err:
dev->stats.tx_errors++;
kfree_skb(skb);
return NETDEV_TX_OK;
}
static int vti4_err(struct sk_buff *skb, u32 info)

10
net/ipv6/ip6_gre.c
View File

@ -881,6 +881,9 @@ static netdev_tx_t ip6gre_tunnel_xmit(struct sk_buff *skb,
struct net_device_stats *stats = &t->dev->stats;
int ret;
if (!pskb_inet_may_pull(skb))
goto tx_err;
if (!ip6_tnl_xmit_ctl(t, &t->parms.laddr, &t->parms.raddr))
goto tx_err;
@ -923,6 +926,9 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
int nhoff;
int thoff;
if (!pskb_inet_may_pull(skb))
goto tx_err;
if (!ip6_tnl_xmit_ctl(t, &t->parms.laddr, &t->parms.raddr))
goto tx_err;
@ -995,8 +1001,6 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
goto tx_err;
}
} else {
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
switch (skb->protocol) {
case htons(ETH_P_IP):
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
@ -1004,7 +1008,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
&dsfield, &encap_limit);
break;
case htons(ETH_P_IPV6):
if (ipv6_addr_equal(&t->parms.raddr, &ipv6h->saddr))
if (ipv6_addr_equal(&t->parms.raddr, &ipv6_hdr(skb)->saddr))
goto tx_err;
if (prepare_ip6gre_xmit_ipv6(skb, dev, &fl6,
&dsfield, &encap_limit))

10
net/ipv6/ip6_tunnel.c
View File

@ -1243,10 +1243,6 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
u8 tproto;
int err;
/* ensure we can access the full inner ip header */
if (!pskb_may_pull(skb, sizeof(struct iphdr)))
return -1;
iph = ip_hdr(skb);
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
@ -1321,9 +1317,6 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
u8 tproto;
int err;
if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
return -1;
ipv6h = ipv6_hdr(skb);
tproto = READ_ONCE(t->parms.proto);
if ((tproto != IPPROTO_IPV6 && tproto != 0) ||
@ -1405,6 +1398,9 @@ ip6_tnl_start_xmit(struct sk_buff *skb, struct net_device *dev)
struct net_device_stats *stats = &t->dev->stats;
int ret;
if (!pskb_inet_may_pull(skb))
goto tx_err;
switch (skb->protocol) {
case htons(ETH_P_IP):
ret = ip4ip6_tnl_xmit(skb, dev);

8
net/ipv6/ip6_vti.c
View File

@ -522,18 +522,18 @@ vti6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct ip6_tnl *t = netdev_priv(dev);
struct net_device_stats *stats = &t->dev->stats;
struct ipv6hdr *ipv6h;
struct flowi fl;
int ret;
if (!pskb_inet_may_pull(skb))
goto tx_err;
memset(&fl, 0, sizeof(fl));
switch (skb->protocol) {
case htons(ETH_P_IPV6):
ipv6h = ipv6_hdr(skb);
if ((t->parms.proto != IPPROTO_IPV6 && t->parms.proto != 0) ||
vti6_addr_conflict(t, ipv6h))
vti6_addr_conflict(t, ipv6_hdr(skb)))
goto tx_err;
xfrm_decode_session(skb, &fl, AF_INET6);

17
net/ipv6/ip6mr.c
View File

@ -51,6 +51,7 @@
#include <linux/export.h>
#include <net/ip6_checksum.h>
#include <linux/netconf.h>
#include <net/ip_tunnels.h>
#include <linux/nospec.h>
@ -599,13 +600,12 @@ static netdev_tx_t reg_vif_xmit(struct sk_buff *skb,
.flowi6_iif = skb->skb_iif ? : LOOPBACK_IFINDEX,
.flowi6_mark = skb->mark,
};
int err;
err = ip6mr_fib_lookup(net, &fl6, &mrt);
if (err < 0) {
kfree_skb(skb);
return err;
}
if (!pskb_inet_may_pull(skb))
goto tx_err;
if (ip6mr_fib_lookup(net, &fl6, &mrt) < 0)
goto tx_err;
read_lock(&mrt_lock);
dev->stats.tx_bytes += skb->len;
@ -614,6 +614,11 @@ static netdev_tx_t reg_vif_xmit(struct sk_buff *skb,
read_unlock(&mrt_lock);
kfree_skb(skb);
return NETDEV_TX_OK;
tx_err:
dev->stats.tx_errors++;
kfree_skb(skb);
return NETDEV_TX_OK;
}
static int reg_vif_get_iflink(const struct net_device *dev)

3
net/ipv6/sit.c
View File

@ -1021,6 +1021,9 @@ tx_error:
static netdev_tx_t sit_tunnel_xmit(struct sk_buff *skb,
struct net_device *dev)
{
if (!pskb_inet_may_pull(skb))
goto tx_err;
switch (skb->protocol) {
case htons(ETH_P_IP):
sit_tunnel_xmit__(skb, dev, IPPROTO_IPIP);