[bpf-next PATCH] bpf: sockmap, fix crash when ipv6 sock is added

John Fastabend
2018-06-04T15:21:30Z

This fixes a crash where we assign tcp_prot to IPv6 sockets instead
of tcpv6_prot.

Previously we overwrote the sk->prot field with tcp_prot even in the
AF_INET6 case. This patch ensures the correct tcp_prot and tcpv6_prot
are used. Further, only allow ESTABLISHED connections to join the
map per note in TLS ULP,

/* The TLS ulp is currently supported only for TCP sockets
* in ESTABLISHED state.
* Supporting sockets in LISTEN state will require us
* to modify the accept implementation to clone rather then
* share the ulp context.
*/

Also tested with 'netserver -6' and 'netperf -H [IPv6]' as well as
'netperf -H [IPv4]'. The ESTABLISHED check resolves the previously
crashing case here.

Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support")
Reported-by: syzbot+5c063698bdbfac19f363@syzkaller.appspotmail.com
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Wei Wang <weiwan@google.com>
---
kernel/bpf/sockmap.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 52a91d8..9e80118 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -41,6 +41,7 @@
#include <linux/mm.h>
#include <net/strparser.h>
#include <net/tcp.h>
+#include <net/transp_v6.h>
#include <linux/ptr_ring.h>
#include <net/inet_common.h>
#include <linux/sched/signal.h>
@@ -162,6 +163,8 @@ static bool bpf_tcp_stream_read(const struct sock *sk)
}

static struct proto tcp_bpf_proto;
+static struct proto tcpv6_bpf_proto;
+
static int bpf_tcp_init(struct sock *sk)
{
struct smap_psock *psock;
@@ -182,13 +185,21 @@ static int bpf_tcp_init(struct sock *sk)
psock->sk_proto = sk->sk_prot;

if (psock->bpf_tx_msg) {
+ tcpv6_bpf_proto.sendmsg = bpf_tcp_sendmsg;
+ tcpv6_bpf_proto.sendpage = bpf_tcp_sendpage;
+ tcpv6_bpf_proto.recvmsg = bpf_tcp_recvmsg;
+ tcpv6_bpf_proto.stream_memory_read = bpf_tcp_stream_read;
tcp_bpf_proto.sendmsg = bpf_tcp_sendmsg;
tcp_bpf_proto.sendpage = bpf_tcp_sendpage;
tcp_bpf_proto.recvmsg = bpf_tcp_recvmsg;
tcp_bpf_proto.stream_memory_read = bpf_tcp_stream_read;
}

- sk->sk_prot = &tcp_bpf_proto;
+ if (sk->sk_family == AF_INET6)
+ sk->sk_prot = &tcpv6_bpf_proto;
+ else
+ sk->sk_prot = &tcp_bpf_proto;
+
rcu_read_unlock();
return 0;
}
@@ -1113,6 +1124,8 @@ static int bpf_tcp_ulp_register(void)
{
tcp_bpf_proto = tcp_prot;
tcp_bpf_proto.close = bpf_tcp_close;
+ tcpv6_bpf_proto = tcpv6_prot;
+ tcpv6_bpf_proto.close = bpf_tcp_close;
/* Once BPF TX ULP is registered it is never unregistered. It
* will be in the ULP list for the lifetime of the system. Doing
* duplicate registers is not a problem.
@@ -1716,6 +1729,14 @@ static int __sock_map_ctx_update_elem(struct bpf_map *map,
bool new = false;
int err = 0;

+ /* ULPs are currently supported only for TCP sockets in ESTABLISHED
+ * state. Supporting sockets in LISTEN state will require us to
+ * modify the accept implementation to clone rather then share the
+ * ulp context.
+ */
+ if (sock->sk_state != TCP_ESTABLISHED)
+ return -ENOTSUPP;
+
/* 1. If sock map has BPF programs those will be inherited by the
* sock being added. If the sock is already attached to BPF programs
* this results in an error.