[v4,bpf-next,1/3] bpf: Invoke cgroup/connect{4,6} programs for unprivileged ICMP ping

Commit Message

YiFei Zhu Sept. 9, 2022, 12:49 a.m. UTC

Usually when a TCP/UDP connection is initiated, we can bind the socket
to a specific IP attached to an interface in a cgroup/connect hook.
But for pings, this is impossible, as the hook is not being called.

This adds the hook invocation to unprivileged ICMP ping (i.e. ping
sockets created with SOCK_DGRAM IPPROTO_ICMP(V6) as opposed to
SOCK_RAW. Logic is mirrored from UDP sockets where the hook is invoked
during pre_connect, after a check for suficiently sized addr_len.

Signed-off-by: YiFei Zhu <[e-mail]>
---
 net/ipv4/ping.c | 15 +++++++++++++++
 net/ipv6/ping.c | 16 ++++++++++++++++
 2 files changed, 31 insertions(+)

Patch

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index b83c2bd9d7223..517042caf6dc1 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -33,6 +33,7 @@ 
 #include <linux/skbuff.h>
 #include <linux/proc_fs.h>
 #include <linux/export.h>
+#include <linux/bpf-cgroup.h>
 #include <net/sock.h>
 #include <net/ping.h>
 #include <net/udp.h>
@@ -295,6 +296,19 @@  void ping_close(struct sock *sk, long timeout)
 }
 EXPORT_SYMBOL_GPL(ping_close);
 
+static int ping_pre_connect(struct sock *sk, struct sockaddr *uaddr,
+			    int addr_len)
+{
+	/* This check is replicated from __ip4_datagram_connect() and
+	 * intended to prevent BPF program called below from accessing bytes
+	 * that are out of the bound specified by user in addr_len.
+	 */
+	if (addr_len < sizeof(struct sockaddr_in))
+		return -EINVAL;
+
+	return BPF_CGROUP_RUN_PROG_INET4_CONNECT_LOCK(sk, uaddr);
+}
+
 /* Checks the bind address and possibly modifies sk->sk_bound_dev_if. */
 static int ping_check_bind_addr(struct sock *sk, struct inet_sock *isk,
 				struct sockaddr *uaddr, int addr_len)
@@ -1009,6 +1023,7 @@  struct proto ping_prot = {
 	.owner =	THIS_MODULE,
 	.init =		ping_init_sock,
 	.close =	ping_close,
+	.pre_connect =	ping_pre_connect,
 	.connect =	ip4_datagram_connect,
 	.disconnect =	__udp_disconnect,
 	.setsockopt =	ip_setsockopt,
diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index 91b8405146569..5f2ef84937142 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c
@@ -20,6 +20,7 @@ 
 #include <net/udp.h>
 #include <net/transp_v6.h>
 #include <linux/proc_fs.h>
+#include <linux/bpf-cgroup.h>
 #include <net/ping.h>
 
 static void ping_v6_destroy(struct sock *sk)
@@ -49,6 +50,20 @@  static int dummy_ipv6_chk_addr(struct net *net, const struct in6_addr *addr,
 	return 0;
 }
 
+static int ping_v6_pre_connect(struct sock *sk, struct sockaddr *uaddr,
+			       int addr_len)
+{
+	/* This check is replicated from __ip6_datagram_connect() and
+	 * intended to prevent BPF program called below from accessing
+	 * bytes that are out of the bound specified by user in addr_len.
+	 */
+
+	if (addr_len < SIN6_LEN_RFC2133)
+		return -EINVAL;
+
+	return BPF_CGROUP_RUN_PROG_INET6_CONNECT_LOCK(sk, uaddr);
+}
+
 static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
 	struct inet_sock *inet = inet_sk(sk);
@@ -191,6 +206,7 @@  struct proto pingv6_prot = {
 	.init =		ping_init_sock,
 	.close =	ping_close,
 	.destroy =	ping_v6_destroy,
+	.pre_connect =	ping_v6_pre_connect,
 	.connect =	ip6_datagram_connect_v6_only,
 	.disconnect =	__udp_disconnect,
 	.setsockopt =	ipv6_setsockopt,