tipc: fix race between poll() and setsockopt()

Letting tipc_poll() dereference a socket's pointer to struct tipc_group
entails a race risk, as the group item may be deleted in a concurrent
tipc_sk_join() or tipc_sk_leave() thread.

We now move the 'open' flag in struct tipc_group to struct tipc_sock,
and let the former retain only a pointer to the moved field. This will
eliminate the race risk.

Reported-by: syzbot+799dafde0286795858ac@syzkaller.appspotmail.com
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tipc/group.c b/net/tipc/group.c
index 497ee34bfab96079807be633d37a36f5cc7b4745..122162a3181648bad80f110cb94291f4a282e81f 100644 (file)
--- a/net/tipc/group.c
+++ b/net/tipc/group.c
@@ -93,26 +93,21 @@ struct tipc_group {
        u16 max_active;
        u16 bc_snd_nxt;
        u16 bc_ackers;
+       bool *open;
        bool loopback;
        bool events;
-       bool open;
 };
 
 static void tipc_group_proto_xmit(struct tipc_group *grp, struct tipc_member *m,
                                  int mtyp, struct sk_buff_head *xmitq);
 
-bool tipc_group_is_open(struct tipc_group *grp)
-{
-       return grp->open;
-}
-
 static void tipc_group_open(struct tipc_member *m, bool *wakeup)
 {
        *wakeup = false;
        if (list_empty(&m->small_win))
                return;
        list_del_init(&m->small_win);
-       m->group->open = true;
+       *m->group->open = true;
        *wakeup = true;
 }
 
@@ -170,7 +165,8 @@ int tipc_group_size(struct tipc_group *grp)
 }
 
 struct tipc_group *tipc_group_create(struct net *net, u32 portid,
-                                    struct tipc_group_req *mreq)
+                                    struct tipc_group_req *mreq,
+                                    bool *group_is_open)
 {
        u32 filter = TIPC_SUB_PORTS | TIPC_SUB_NO_STATUS;
        bool global = mreq->scope != TIPC_NODE_SCOPE;
@@ -192,6 +188,7 @@ struct tipc_group *tipc_group_create(struct net *net, u32 portid,
        grp->scope = mreq->scope;
        grp->loopback = mreq->flags & TIPC_GROUP_LOOPBACK;
        grp->events = mreq->flags & TIPC_GROUP_MEMBER_EVTS;
+       grp->open = group_is_open;
        filter |= global ? TIPC_SUB_CLUSTER_SCOPE : TIPC_SUB_NODE_SCOPE;
        if (tipc_topsrv_kern_subscr(net, portid, type, 0, ~0,
                                    filter, &grp->subid))
@@ -430,7 +427,7 @@ bool tipc_group_cong(struct tipc_group *grp, u32 dnode, u32 dport,
        if (m->window >= len)
                return false;
 
-       grp->open = false;
+       *grp->open = false;
 
        /* If not fully advertised, do it now to prevent mutual blocking */
        adv = m->advertised;
@@ -453,7 +450,7 @@ bool tipc_group_bc_cong(struct tipc_group *grp, int len)
 
        /* If prev bcast was replicast, reject until all receivers have acked */
        if (grp->bc_ackers) {
-               grp->open = false;
+               *grp->open = false;
                return true;
        }
        if (list_empty(&grp->small_win))
@@ -800,7 +797,7 @@ void tipc_group_proto_rcv(struct tipc_group *grp, bool *usr_wakeup,
                if (--grp->bc_ackers)
                        return;
                list_del_init(&m->small_win);
-               m->group->open = true;
+               *m->group->open = true;
                *usr_wakeup = true;
                tipc_group_update_member(m, 0);
                return;

diff --git a/net/tipc/group.h b/net/tipc/group.h
index f4a596ed98487c879442872db668e9f4b2da78ec..5996af6e9f1ddb72b565ae9288e685c83d6a1c0d 100644 (file)
--- a/net/tipc/group.h
+++ b/net/tipc/group.h
@@ -43,7 +43,8 @@ struct tipc_member;
 struct tipc_msg;
 
 struct tipc_group *tipc_group_create(struct net *net, u32 portid,
-                                    struct tipc_group_req *mreq);
+                                    struct tipc_group_req *mreq,
+                                    bool *group_is_open);
 void tipc_group_join(struct net *net, struct tipc_group *grp, int *sk_rcv_buf);
 void tipc_group_delete(struct net *net, struct tipc_group *grp);
 void tipc_group_add_member(struct tipc_group *grp, u32 node,
@@ -67,7 +68,6 @@ void tipc_group_update_bc_members(struct tipc_group *grp, int len, bool ack);
 bool tipc_group_cong(struct tipc_group *grp, u32 dnode, u32 dport,
                     int len, struct tipc_member **m);
 bool tipc_group_bc_cong(struct tipc_group *grp, int len);
-bool tipc_group_is_open(struct tipc_group *grp);
 void tipc_group_update_rcv_win(struct tipc_group *grp, int blks, u32 node,
                               u32 port, struct sk_buff_head *xmitq);
 u16 tipc_group_bc_snd_nxt(struct tipc_group *grp);

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index d799e50ff7222f4cb3fb4215a5d19dca313a44b1..473a096b6fba9a90aa116666b63f97da9c1e3202 100644 (file)
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -116,6 +116,7 @@ struct tipc_sock {
        struct tipc_mc_method mc_method;
        struct rcu_head rcu;
        struct tipc_group *group;
+       bool group_is_open;
 };
 
 static int tipc_sk_backlog_rcv(struct sock *sk, struct sk_buff *skb);
@@ -715,7 +716,6 @@ static unsigned int tipc_poll(struct file *file, struct socket *sock,
 {
        struct sock *sk = sock->sk;
        struct tipc_sock *tsk = tipc_sk(sk);
-       struct tipc_group *grp;
        u32 revents = 0;
 
        sock_poll_wait(file, sk_sleep(sk), wait);
@@ -736,8 +736,7 @@ static unsigned int tipc_poll(struct file *file, struct socket *sock,
                        revents |= POLLIN | POLLRDNORM;
                break;
        case TIPC_OPEN:
-               grp = tsk->group;
-               if ((!grp || tipc_group_is_open(grp)) && !tsk->cong_link_cnt)
+               if (tsk->group_is_open && !tsk->cong_link_cnt)
                        revents |= POLLOUT;
                if (!tipc_sk_type_connectionless(sk))
                        break;
@@ -2758,7 +2757,7 @@ static int tipc_sk_join(struct tipc_sock *tsk, struct tipc_group_req *mreq)
                return -EINVAL;
        if (grp)
                return -EACCES;
-       grp = tipc_group_create(net, tsk->portid, mreq);
+       grp = tipc_group_create(net, tsk->portid, mreq, &tsk->group_is_open);
        if (!grp)
                return -ENOMEM;
        tsk->group = grp;