[PATCH 4.20 009/145] ip: validate header length on virtual device xmit

4.20-stable review patch. If anyone has any objections, please let me know.

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From: Willem de Bruijn willemb@google.com

[ Upstream commit cb9f1b783850b14cbd7f87d061d784a666dfba1f ]

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 76c0ddd8c3a6 ("ip6_tunnel: be careful when accessing the inner header") and commit ccfec9e5cb2d ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/ip_tunnels.h | 20 ++++++++++++++++++++ net/ipv4/ip_gre.c | 9 +++++++++ net/ipv4/ip_tunnel.c | 9 --------- net/ipv4/ip_vti.c | 12 +++++++++--- net/ipv6/ip6_gre.c | 10 +++++++--- net/ipv6/ip6_tunnel.c | 10 +++------- net/ipv6/ip6_vti.c | 8 ++++---- net/ipv6/ip6mr.c | 17 +++++++++++------ net/ipv6/sit.c | 3 +++ 9 files changed, 66 insertions(+), 32 deletions(-)

--- a/include/net/ip_tunnels.h +++ b/include/net/ip_tunnels.h @@ -307,6 +307,26 @@ int ip_tunnel_encap_del_ops(const struct 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; --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -674,6 +674,9 @@ static netdev_tx_t ipgre_xmit(struct sk_ 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; @@ -717,6 +720,9 @@ static netdev_tx_t erspan_xmit(struct sk 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; @@ -760,6 +766,9 @@ static netdev_tx_t gre_tap_xmit(struct s { 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; --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -627,7 +627,6 @@ void ip_tunnel_xmit(struct sk_buff *skb, 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, __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);

--- a/net/ipv4/ip_vti.c +++ b/net/ipv4/ip_vti.c @@ -241,6 +241,9 @@ static netdev_tx_t vti_tunnel_xmit(struc 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(struc 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) --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -879,6 +879,9 @@ static netdev_tx_t ip6gre_tunnel_xmit(st 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;

@@ -921,6 +924,9 @@ static netdev_tx_t ip6erspan_tunnel_xmit 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;

@@ -993,8 +999,6 @@ static netdev_tx_t ip6erspan_tunnel_xmit 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)); @@ -1002,7 +1006,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit &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)) --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -1243,10 +1243,6 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, str 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, str 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_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); --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -522,18 +522,18 @@ vti6_tnl_xmit(struct sk_buff *skb, struc { 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); --- a/net/ipv6/ip6mr.c +++ b/net/ipv6/ip6mr.c @@ -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 s .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 s 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) --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -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);