netdev - [PATCH bpf 1/5] tcp, ulp: add alias for all ulp modules

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Date:   Thu, 16 Aug 2018 21:49:06 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     alexei.starovoitov@...il.com
Cc:     john.fastabend@...il.com, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf 1/5] tcp, ulp: add alias for all ulp modules

Lets not turn the TCP ULP lookup into an arbitrary module loader as
we only intend to load ULP modules through this mechanism, not other
unrelated kernel modules:

  [root@bar]# cat foo.c
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <linux/tcp.h>
  #include <linux/in.h>

  int main(void)
  {
      int sock = socket(PF_INET, SOCK_STREAM, 0);
      setsockopt(sock, IPPROTO_TCP, TCP_ULP, "sctp", sizeof("sctp"));
      return 0;
  }

  [root@bar]# gcc foo.c -O2 -Wall
  [root@bar]# lsmod | grep sctp
  [root@bar]# ./a.out
  [root@bar]# lsmod | grep sctp
  sctp                 1077248  4
  libcrc32c              16384  3 nf_conntrack,nf_nat,sctp
  [root@bar]#

Fix it by adding module alias to TCP ULP modules, so probing module
via request_module() will be limited to tcp-ulp-[name]. The existing
modules like kTLS will load fine given tcp-ulp-tls alias, but others
will fail to load:

  [root@bar]# lsmod | grep sctp
  [root@bar]# ./a.out
  [root@bar]# lsmod | grep sctp
  [root@bar]#

Sockmap is not affected from this since it's either built-in or not.

Fixes: 734942cc4ea6 ("tcp: ULP infrastructure")
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: John Fastabend <john.fastabend@...il.com>
---
 include/net/tcp.h  | 4 ++++
 net/ipv4/tcp_ulp.c | 2 +-
 net/tls/tls_main.c | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index d196901..770917d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2065,6 +2065,10 @@ int tcp_set_ulp_id(struct sock *sk, const int ulp);
 void tcp_get_available_ulp(char *buf, size_t len);
 void tcp_cleanup_ulp(struct sock *sk);
 
+#define MODULE_ALIAS_TCP_ULP(name)				\
+	__MODULE_INFO(alias, alias_userspace, name);		\
+	__MODULE_INFO(alias, alias_tcp_ulp, "tcp-ulp-" name)
+
 /* Call BPF_SOCK_OPS program that returns an int. If the return value
  * is < 0, then the BPF op failed (for example if the loaded BPF
  * program does not support the chosen operation or there is no BPF
diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c
index 622caa4..7dd44b6 100644
--- a/net/ipv4/tcp_ulp.c
+++ b/net/ipv4/tcp_ulp.c
@@ -51,7 +51,7 @@ static const struct tcp_ulp_ops *__tcp_ulp_find_autoload(const char *name)
 #ifdef CONFIG_MODULES
 	if (!ulp && capable(CAP_NET_ADMIN)) {
 		rcu_read_unlock();
-		request_module("%s", name);
+		request_module("tcp-ulp-%s", name);
 		rcu_read_lock();
 		ulp = tcp_ulp_find(name);
 	}
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index b09867c..93c0c22 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -45,6 +45,7 @@
 MODULE_AUTHOR("Mellanox Technologies");
 MODULE_DESCRIPTION("Transport Layer Security Support");
 MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS_TCP_ULP("tls");
 
 enum {
 	TLSV4,
-- 
2.9.5