Re: [BUG] A panic caused by null pointer dereference aftering updating to

From: Eric Dumazet
Date: Mon Apr 14 2014 - 20:14:12 EST

On Mon, 2014-04-14 at 18:51 -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> Date: Mon, 14 Apr 2014 14:23:24 -0700
>
> > I was trying to cook a not too invasive patch.
> >
> > Changing ip_local_out() means changing dst_output() / nf_hook() and
> > hundred of call sites.
> >
> > Unless I misunderstood you ?
>
> You could make ip_local_out(skb) be __ip_local_out(skb, skb->sk) and
> make tunnel output use __ip_local_out().

OK lets try ;)

Zhan, could you try following patch, thanks !

drivers/net/vxlan.c | 4 ++--
include/net/dst.h | 14 +++++++++++---
include/net/inet6_connection_sock.h | 2 +-
include/net/inet_connection_sock.h | 2 +-
include/net/ip.h | 13 +++++++++----
include/net/ip_tunnels.h | 2 +-
net/core/dst.c | 4 ++--
net/dccp/output.c | 2 +-
net/ipv4/ip_output.c | 16 ++++++++--------
net/ipv4/ip_tunnel.c | 2 +-
net/ipv4/ip_tunnel_core.c | 4 ++--
net/ipv4/route.c | 4 ++--
net/ipv4/tcp_output.c | 2 +-
net/ipv6/inet6_connection_sock.c | 3 +--
net/ipv6/sit.c | 5 +++--
net/l2tp/l2tp_core.c | 4 ++--
net/l2tp/l2tp_ip.c | 2 +-
net/openvswitch/vport-gre.c | 2 +-
net/sctp/protocol.c | 2 +-
19 files changed, 51 insertions(+), 38 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index c55e316373a1..82355d5d155a 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1755,8 +1755,8 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
if (err)
return err;

- return iptunnel_xmit(rt, skb, src, dst, IPPROTO_UDP, tos, ttl, df,
- false);
+ return iptunnel_xmit(vs->sock->sk, rt, skb, src, dst, IPPROTO_UDP,
+ tos, ttl, df, false);
}
EXPORT_SYMBOL_GPL(vxlan_xmit_skb);

diff --git a/include/net/dst.h b/include/net/dst.h
index 46ed958e0c6e..71c60f42be48 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -45,7 +45,7 @@ struct dst_entry {
void *__pad1;
#endif
int (*input)(struct sk_buff *);
- int (*output)(struct sk_buff *);
+ int (*output)(struct sock *sk, struct sk_buff *skb);

unsigned short flags;
#define DST_HOST 0x0001
@@ -367,7 +367,11 @@ static inline struct dst_entry *skb_dst_pop(struct sk_buff *skb)
return child;
}

-int dst_discard(struct sk_buff *skb);
+int dst_discard_sk(struct sock *sk, struct sk_buff *skb);
+static inline int dst_discard(struct sk_buff *skb)
+{
+ return dst_discard_sk(skb->sk, skb);
+}
void *dst_alloc(struct dst_ops *ops, struct net_device *dev, int initial_ref,
int initial_obsolete, unsigned short flags);
void __dst_free(struct dst_entry *dst);
@@ -449,9 +453,13 @@ static inline void dst_set_expires(struct dst_entry *dst, int timeout)
}

/* Output packet to network from transport. */
+static inline int dst_output_sk(struct sock *sk, struct sk_buff *skb)
+{
+ return skb_dst(skb)->output(sk, skb);
+}
static inline int dst_output(struct sk_buff *skb)
{
- return skb_dst(skb)->output(skb);
+ return dst_output_sk(skb->sk, skb);
}

/* Input packet from network to transport. */
diff --git a/include/net/inet6_connection_sock.h b/include/net/inet6_connection_sock.h
index f981ba7adeed..74af137304be 100644
--- a/include/net/inet6_connection_sock.h
+++ b/include/net/inet6_connection_sock.h
@@ -40,7 +40,7 @@ void inet6_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,

void inet6_csk_addr2sockaddr(struct sock *sk, struct sockaddr *uaddr);

-int inet6_csk_xmit(struct sk_buff *skb, struct flowi *fl);
+int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl);

struct dst_entry *inet6_csk_update_pmtu(struct sock *sk, u32 mtu);
#endif /* _INET6_CONNECTION_SOCK_H */
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index c55aeed41ace..7a4313887568 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -36,7 +36,7 @@ struct tcp_congestion_ops;
* (i.e. things that depend on the address family)
*/
struct inet_connection_sock_af_ops {
- int (*queue_xmit)(struct sk_buff *skb, struct flowi *fl);
+ int (*queue_xmit)(struct sock *sk, struct sk_buff *skb, struct flowi *fl);
void (*send_check)(struct sock *sk, struct sk_buff *skb);
int (*rebuild_header)(struct sock *sk);
void (*sk_rx_dst_set)(struct sock *sk, const struct sk_buff *skb);
diff --git a/include/net/ip.h b/include/net/ip.h
index 25064c28e059..3ec2b0fb9d83 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -104,14 +104,19 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
struct net_device *orig_dev);
int ip_local_deliver(struct sk_buff *skb);
int ip_mr_input(struct sk_buff *skb);
-int ip_output(struct sk_buff *skb);
-int ip_mc_output(struct sk_buff *skb);
+int ip_output(struct sock *sk, struct sk_buff *skb);
+int ip_mc_output(struct sock *sk, struct sk_buff *skb);
int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
int ip_do_nat(struct sk_buff *skb);
void ip_send_check(struct iphdr *ip);
int __ip_local_out(struct sk_buff *skb);
-int ip_local_out(struct sk_buff *skb);
-int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl);
+int ip_local_out_sk(struct sock *sk, struct sk_buff *skb);
+static inline int ip_local_out(struct sk_buff *skb)
+{
+ return ip_local_out_sk(skb->sk, skb);
+}
+
+int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl);
void ip_init(void);
int ip_append_data(struct sock *sk, struct flowi4 *fl4,
int getfrag(void *from, char *to, int offset, int len,
diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index e77c10405d51..a4daf9eb8562 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -153,7 +153,7 @@ static inline u8 ip_tunnel_ecn_encap(u8 tos, const struct iphdr *iph,
}

int iptunnel_pull_header(struct sk_buff *skb, int hdr_len, __be16 inner_proto);
-int iptunnel_xmit(struct rtable *rt, struct sk_buff *skb,
+int iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
__be32 src, __be32 dst, __u8 proto,
__u8 tos, __u8 ttl, __be16 df, bool xnet);

diff --git a/net/core/dst.c b/net/core/dst.c
index ca4231ec7347..7443c2725c9c 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -142,12 +142,12 @@ loop:
mutex_unlock(&dst_gc_mutex);
}

-int dst_discard(struct sk_buff *skb)
+int dst_discard_sk(struct sock *sk, struct sk_buff *skb)
{
kfree_skb(skb);
return 0;
}
-EXPORT_SYMBOL(dst_discard);
+EXPORT_SYMBOL(dst_discard_sk);

const u32 dst_default_metrics[RTAX_MAX + 1] = {
/* This initializer is needed to force linker to place this variable
diff --git a/net/dccp/output.c b/net/dccp/output.c
index 8876078859da..0248e8a3460c 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -138,7 +138,7 @@ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)

DCCP_INC_STATS(DCCP_MIB_OUTSEGS);

- err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl);
+ err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
return net_xmit_eval(err);
}
return -ENOBUFS;
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 1a0755fea491..1cbeba5edff9 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -101,17 +101,17 @@ int __ip_local_out(struct sk_buff *skb)
skb_dst(skb)->dev, dst_output);
}

-int ip_local_out(struct sk_buff *skb)
+int ip_local_out_sk(struct sock *sk, struct sk_buff *skb)
{
int err;

err = __ip_local_out(skb);
if (likely(err == 1))
- err = dst_output(skb);
+ err = dst_output_sk(sk, skb);

return err;
}
-EXPORT_SYMBOL_GPL(ip_local_out);
+EXPORT_SYMBOL_GPL(ip_local_out_sk);

static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
{
@@ -226,9 +226,8 @@ static int ip_finish_output(struct sk_buff *skb)
return ip_finish_output2(skb);
}

-int ip_mc_output(struct sk_buff *skb)
+int ip_mc_output(struct sock *sk, struct sk_buff *skb)
{
- struct sock *sk = skb->sk;
struct rtable *rt = skb_rtable(skb);
struct net_device *dev = rt->dst.dev;

@@ -287,7 +286,7 @@ int ip_mc_output(struct sk_buff *skb)
!(IPCB(skb)->flags & IPSKB_REROUTED));
}

-int ip_output(struct sk_buff *skb)
+int ip_output(struct sock *sk, struct sk_buff *skb)
{
struct net_device *dev = skb_dst(skb)->dev;

@@ -315,9 +314,9 @@ static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
sizeof(fl4->saddr) + sizeof(fl4->daddr));
}

-int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl)
+/* Note: skb->sk can be different from sk, in case of tunnels */
+int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
{
- struct sock *sk = skb->sk;
struct inet_sock *inet = inet_sk(sk);
struct ip_options_rcu *inet_opt;
struct flowi4 *fl4;
@@ -389,6 +388,7 @@ packet_routed:
ip_select_ident_more(skb, &rt->dst, sk,
(skb_shinfo(skb)->gso_segs ?: 1) - 1);

+ /* TODO : should we use skb->sk here instead of sk ? */
skb->priority = sk->sk_priority;
skb->mark = sk->sk_mark;

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index e77381d1df9a..484d0ce27ef7 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -670,7 +670,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
return;
}

- err = iptunnel_xmit(rt, skb, fl4.saddr, fl4.daddr, protocol,
+ err = iptunnel_xmit(skb->sk, rt, skb, fl4.saddr, fl4.daddr, protocol,
tos, ttl, df, !net_eq(tunnel->net, dev_net(dev)));
iptunnel_xmit_stats(err, &dev->stats, dev->tstats);

diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index e0c2b1d2ea4e..bcf206c79005 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -46,7 +46,7 @@
#include <net/netns/generic.h>
#include <net/rtnetlink.h>

-int iptunnel_xmit(struct rtable *rt, struct sk_buff *skb,
+int iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
__be32 src, __be32 dst, __u8 proto,
__u8 tos, __u8 ttl, __be16 df, bool xnet)
{
@@ -76,7 +76,7 @@ int iptunnel_xmit(struct rtable *rt, struct sk_buff *skb,
iph->ttl = ttl;
__ip_select_ident(iph, &rt->dst, (skb_shinfo(skb)->gso_segs ?: 1) - 1);

- err = ip_local_out(skb);
+ err = ip_local_out_sk(sk, skb);
if (unlikely(net_xmit_eval(err)))
pkt_len = 0;
return pkt_len;
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 34d094cadb11..f2279d4470c4 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1129,7 +1129,7 @@ static void ipv4_link_failure(struct sk_buff *skb)
dst_set_expires(&rt->dst, 0);
}

-static int ip_rt_bug(struct sk_buff *skb)
+static int ip_rt_bug(struct sock *sk, struct sk_buff *skb)
{
pr_debug("%s: %pI4 -> %pI4, %s\n",
__func__, &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
@@ -2218,7 +2218,7 @@ struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_or

new->__use = 1;
new->input = dst_discard;
- new->output = dst_discard;
+ new->output = dst_discard_sk;

new->dev = ort->dst.dev;
if (new->dev)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 699fb102e971..025e25093984 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -981,7 +981,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
tcp_skb_pcount(skb));

- err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl);
+ err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
if (likely(err <= 0))
return err;

diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index c9138189415a..d4ade34ab375 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -224,9 +224,8 @@ static struct dst_entry *inet6_csk_route_socket(struct sock *sk,
return dst;
}

-int inet6_csk_xmit(struct sk_buff *skb, struct flowi *fl_unused)
+int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl_unused)
{
- struct sock *sk = skb->sk;
struct ipv6_pinfo *np = inet6_sk(sk);
struct flowi6 fl6;
struct dst_entry *dst;
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 1693c8d885f0..8da8268d65f8 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -974,8 +974,9 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
goto out;
}

- err = iptunnel_xmit(rt, skb, fl4.saddr, fl4.daddr, IPPROTO_IPV6, tos,
- ttl, df, !net_eq(tunnel->net, dev_net(dev)));
+ err = iptunnel_xmit(skb->sk, rt, skb, fl4.saddr, fl4.daddr,
+ IPPROTO_IPV6, tos, ttl, df,
+ !net_eq(tunnel->net, dev_net(dev)));
iptunnel_xmit_stats(err, &dev->stats, dev->tstats);
return NETDEV_TX_OK;

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 47f7a5490555..a4e37d7158dc 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1131,10 +1131,10 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
skb->local_df = 1;
#if IS_ENABLED(CONFIG_IPV6)
if (tunnel->sock->sk_family == PF_INET6 && !tunnel->v4mapped)
- error = inet6_csk_xmit(skb, NULL);
+ error = inet6_csk_xmit(tunnel->sock, skb, NULL);
else
#endif
- error = ip_queue_xmit(skb, fl);
+ error = ip_queue_xmit(tunnel->sock, skb, fl);

/* Update stats */
if (error >= 0) {
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 0b44d855269c..3397fe6897c0 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -487,7 +487,7 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m

xmit:
/* Queue the packet to IP for output */
- rc = ip_queue_xmit(skb, &inet->cork.fl);
+ rc = ip_queue_xmit(sk, skb, &inet->cork.fl);
rcu_read_unlock();

error:
diff --git a/net/openvswitch/vport-gre.c b/net/openvswitch/vport-gre.c
index a3d6951602db..ebb6e2442554 100644
--- a/net/openvswitch/vport-gre.c
+++ b/net/openvswitch/vport-gre.c
@@ -174,7 +174,7 @@ static int gre_tnl_send(struct vport *vport, struct sk_buff *skb)

skb->local_df = 1;

- return iptunnel_xmit(rt, skb, fl.saddr,
+ return iptunnel_xmit(skb->sk, rt, skb, fl.saddr,
OVS_CB(skb)->tun_key->ipv4_dst, IPPROTO_GRE,
OVS_CB(skb)->tun_key->ipv4_tos,
OVS_CB(skb)->tun_key->ipv4_ttl, df, false);
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 4e1d0fcb028e..c09757fbf803 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -957,7 +957,7 @@ static inline int sctp_v4_xmit(struct sk_buff *skb,

SCTP_INC_STATS(sock_net(&inet->sk), SCTP_MIB_OUTSCTPPACKS);

- return ip_queue_xmit(skb, &transport->fl);
+ return ip_queue_xmit(&inet->sk, skb, &transport->fl);
}

static struct sctp_af sctp_af_inet;


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