tipc: set con sock in tipc_conn_alloc

A crash was reported by Wei Chen:

  BUG: kernel NULL pointer dereference, address: 0000000000000018
  RIP: 0010:tipc_conn_close+0x12/0x100
  Call Trace:
   tipc_topsrv_exit_net+0x139/0x320
   ops_exit_list.isra.9+0x49/0x80
   cleanup_net+0x31a/0x540
   process_one_work+0x3fa/0x9f0
   worker_thread+0x42/0x5c0

It was caused by !con->sock in tipc_conn_close(). In tipc_topsrv_accept(),
con is allocated in conn_idr then its sock is set:

  con = tipc_conn_alloc();
  ...                    <----[1]
  con->sock = newsock;

If tipc_conn_close() is called in anytime of [1], the null-pointer-def
is triggered by con->sock->sk due to con->sock is not yet set.

This patch fixes it by moving the con->sock setting to tipc_conn_alloc()
under s->idr_lock. So that con->sock can never be NULL when getting the
con from s->conn_idr. It will be also safer to move con->server and flag
CF_CONNECTED setting under s->idr_lock, as they should all be set before
tipc_conn_alloc() is called.

Fixes: c5fa7b3cf3cb ("tipc: introduce new TIPC server infrastructure")
Reported-by: Wei Chen <harperchen1110@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c
index d92ec92f0b71d94bf1f8f9c791879b0df5ce0dd4..b0f9aa521670abd6791009a817696f1a4a00bea9 100644 (file)
--- a/net/tipc/topsrv.c
+++ b/net/tipc/topsrv.c
@@ -176,7 +176,7 @@ static void tipc_conn_close(struct tipc_conn *con)
        conn_put(con);
 }
 
-static struct tipc_conn *tipc_conn_alloc(struct tipc_topsrv *s)
+static struct tipc_conn *tipc_conn_alloc(struct tipc_topsrv *s, struct socket *sock)
 {
        struct tipc_conn *con;
        int ret;
@@ -202,10 +202,11 @@ static struct tipc_conn *tipc_conn_alloc(struct tipc_topsrv *s)
        }
        con->conid = ret;
        s->idr_in_use++;
-       spin_unlock_bh(&s->idr_lock);
 
        set_bit(CF_CONNECTED, &con->flags);
        con->server = s;
+       con->sock = sock;
+       spin_unlock_bh(&s->idr_lock);
 
        return con;
 }
@@ -467,7 +468,7 @@ static void tipc_topsrv_accept(struct work_struct *work)
                ret = kernel_accept(lsock, &newsock, O_NONBLOCK);
                if (ret < 0)
                        return;
-               con = tipc_conn_alloc(srv);
+               con = tipc_conn_alloc(srv, newsock);
                if (IS_ERR(con)) {
                        ret = PTR_ERR(con);
                        sock_release(newsock);
@@ -479,7 +480,6 @@ static void tipc_topsrv_accept(struct work_struct *work)
                newsk->sk_data_ready = tipc_conn_data_ready;
                newsk->sk_write_space = tipc_conn_write_space;
                newsk->sk_user_data = con;
-               con->sock = newsock;
                write_unlock_bh(&newsk->sk_callback_lock);
 
                /* Wake up receive process in case of 'SYN+' message */
@@ -577,12 +577,11 @@ bool tipc_topsrv_kern_subscr(struct net *net, u32 port, u32 type, u32 lower,
        sub.filter = filter;
        *(u64 *)&sub.usr_handle = (u64)port;
 
-       con = tipc_conn_alloc(tipc_topsrv(net));
+       con = tipc_conn_alloc(tipc_topsrv(net), NULL);
        if (IS_ERR(con))
                return false;
 
        *conid = con->conid;
-       con->sock = NULL;
        rc = tipc_conn_rcv_sub(tipc_topsrv(net), con, &sub);
        if (rc >= 0)
                return true;