diff mbox series

[net] tipc: add stricter control of reserved service types

Message ID 20201028131912.3773561-1-jmaloy@redhat.com
State New
Headers show
Series [net] tipc: add stricter control of reserved service types | expand

Commit Message

Jon Maloy Oct. 28, 2020, 1:19 p.m. UTC
From: Jon Maloy <jmaloy@redhat.com>

TIPC reserves 64 service types for current and future internal use.
Therefore, the bind() function is meant to block regular user sockets
from being bound to these values, while it should let through such
bindings from internal users.

However, since we at the design moment saw no way to distinguish
between regular and internal users the filter function ended up
with allowing all bindings of the reserved types which were really
in use ([0,1]), and block all the rest ([2,63]).

This is risky, since a regular user may bind to the service type
representing the topology server (TIPC_TOP_SRV == 1) or the one used
for indicating neighboring node status (TIPC_CFG_SRV == 0), and wreak
havoc for users of those services, i.e., most users.

The reality is however that TIPC_CFG_SRV never is bound through the
bind() function, since it doesn't represent a regular socket, and
TIPC_TOP_SRV can also be made to bypass the checks in tipc_bind()
by introducing a different entry function, tipc_sk_bind().

It should be noted that although this is a change of the API semantics,
there is no risk we will break any currently working applications by
doing this. Any application trying to bind to the values in question
would be badly broken from the outset, so there is no chance we would
find any such applications in real-world production systems.

Acked-by: Yung Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 net/tipc/socket.c | 24 +++++++++++++++---------
 net/tipc/socket.h |  2 +-
 net/tipc/topsrv.c |  4 ++--
 3 files changed, 18 insertions(+), 12 deletions(-)

Comments

Jakub Kicinski Oct. 29, 2020, 10:11 p.m. UTC | #1
On Wed, 28 Oct 2020 09:19:12 -0400 jmaloy@redhat.com wrote:
> From: Jon Maloy <jmaloy@redhat.com>

> 

> TIPC reserves 64 service types for current and future internal use.

> Therefore, the bind() function is meant to block regular user sockets

> from being bound to these values, while it should let through such

> bindings from internal users.

> 

> However, since we at the design moment saw no way to distinguish

> between regular and internal users the filter function ended up

> with allowing all bindings of the reserved types which were really

> in use ([0,1]), and block all the rest ([2,63]).

> 

> This is risky, since a regular user may bind to the service type

> representing the topology server (TIPC_TOP_SRV == 1) or the one used

> for indicating neighboring node status (TIPC_CFG_SRV == 0), and wreak

> havoc for users of those services, i.e., most users.

> 

> The reality is however that TIPC_CFG_SRV never is bound through the

> bind() function, since it doesn't represent a regular socket, and

> TIPC_TOP_SRV can also be made to bypass the checks in tipc_bind()

> by introducing a different entry function, tipc_sk_bind().

> 

> It should be noted that although this is a change of the API semantics,

> there is no risk we will break any currently working applications by

> doing this. Any application trying to bind to the values in question

> would be badly broken from the outset, so there is no chance we would

> find any such applications in real-world production systems.


You say above that it would wreak havoc for most users, not all :)

I'd be more comfortable applying this to net-next, does that work for
you? 

Also perhaps we could add a pr_warn_once() if an application tried
using the reserved values, to help identify this change right away.

> Acked-by: Yung Xue <ying.xue@windriver.com>

> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
diff mbox series

Patch

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index e795a8a2955b..222fd53da2d0 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -658,8 +658,8 @@  static int tipc_release(struct socket *sock)
  * NOTE: This routine doesn't need to take the socket lock since it doesn't
  *       access any non-constant socket information.
  */
-static int tipc_bind(struct socket *sock, struct sockaddr *uaddr,
-		     int uaddr_len)
+
+int tipc_sk_bind(struct socket *sock, struct sockaddr *uaddr, int uaddr_len)
 {
 	struct sock *sk = sock->sk;
 	struct sockaddr_tipc *addr = (struct sockaddr_tipc *)uaddr;
@@ -691,13 +691,6 @@  static int tipc_bind(struct socket *sock, struct sockaddr *uaddr,
 		goto exit;
 	}
 
-	if ((addr->addr.nameseq.type < TIPC_RESERVED_TYPES) &&
-	    (addr->addr.nameseq.type != TIPC_TOP_SRV) &&
-	    (addr->addr.nameseq.type != TIPC_CFG_SRV)) {
-		res = -EACCES;
-		goto exit;
-	}
-
 	res = (addr->scope >= 0) ?
 		tipc_sk_publish(tsk, addr->scope, &addr->addr.nameseq) :
 		tipc_sk_withdraw(tsk, -addr->scope, &addr->addr.nameseq);
@@ -706,6 +699,19 @@  static int tipc_bind(struct socket *sock, struct sockaddr *uaddr,
 	return res;
 }
 
+static int tipc_bind(struct socket *sock, struct sockaddr *skaddr, int alen)
+{
+	struct sockaddr_tipc *addr = (struct sockaddr_tipc *)skaddr;
+
+	if (alen) {
+		if (alen < sizeof(struct sockaddr_tipc))
+			return -EINVAL;
+		if (addr->addr.nameseq.type < TIPC_RESERVED_TYPES)
+			return -EACCES;
+	}
+	return tipc_sk_bind(sock, skaddr, alen);
+}
+
 /**
  * tipc_getname - get port ID of socket or peer socket
  * @sock: socket structure
diff --git a/net/tipc/socket.h b/net/tipc/socket.h
index b11575afc66f..02cdf166807d 100644
--- a/net/tipc/socket.h
+++ b/net/tipc/socket.h
@@ -74,7 +74,7 @@  int tipc_dump_done(struct netlink_callback *cb);
 u32 tipc_sock_get_portid(struct sock *sk);
 bool tipc_sk_overlimit1(struct sock *sk, struct sk_buff *skb);
 bool tipc_sk_overlimit2(struct sock *sk, struct sk_buff *skb);
-
+int tipc_sk_bind(struct socket *sock, struct sockaddr *skaddr, int alen);
 int tsk_set_importance(struct sock *sk, int imp);
 
 #endif
diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c
index 5f6f86051c83..cec029349662 100644
--- a/net/tipc/topsrv.c
+++ b/net/tipc/topsrv.c
@@ -520,12 +520,12 @@  static int tipc_topsrv_create_listener(struct tipc_topsrv *srv)
 
 	saddr.family	                = AF_TIPC;
 	saddr.addrtype		        = TIPC_ADDR_NAMESEQ;
-	saddr.addr.nameseq.type	        = TIPC_TOP_SRV;
+	saddr.addr.nameseq.type         = TIPC_TOP_SRV;
 	saddr.addr.nameseq.lower	= TIPC_TOP_SRV;
 	saddr.addr.nameseq.upper	= TIPC_TOP_SRV;
 	saddr.scope			= TIPC_NODE_SCOPE;
 
-	rc = kernel_bind(lsock, (struct sockaddr *)&saddr, sizeof(saddr));
+	rc = tipc_sk_bind(lsock, (struct sockaddr *)&saddr, sizeof(saddr));
 	if (rc < 0)
 		goto err;
 	rc = kernel_listen(lsock, 0);