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sctp: hold transport before accessing its asoc in sctp_transport_get_next 

As Marcelo noticed, in sctp_transport_get_next, it is iterating over
transports but then also accessing the association directly, without
checking any refcnts before that, which can cause an use-after-free
Read.

So fix it by holding transport before accessing the association. With
that, sctp_transport_hold calls can be removed in the later places.

Fixes: 626d16f50f ("sctp: export some apis or variables for sctp_diag and reuse some for proc")
Reported-by: syzbot+fe62a0c9aa6a85c6de16@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xin Long 2018-08-27 18:38:31 +08:00 committed by David S. Miller
parent 050cdc6c95
commit bab1be79a5
2 changed files with 15 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
net/sctp/proc.c
View File

@ -264,8 +264,6 @@ static int sctp_assocs_seq_show(struct seq_file *seq, void *v)
}
transport = (struct sctp_transport *)v;
if (!sctp_transport_hold(transport))
return 0;
assoc = transport->asoc;
epb = &assoc->base;
sk = epb->sk;
@ -322,8 +320,6 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
}
transport = (struct sctp_transport *)v;
if (!sctp_transport_hold(transport))
return 0;
assoc = transport->asoc;
list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,

22
net/sctp/socket.c
View File

@ -5005,9 +5005,14 @@ struct sctp_transport *sctp_transport_get_next(struct net *net,
break;
}
if (!sctp_transport_hold(t))
continue;
if (net_eq(sock_net(t->asoc->base.sk), net) &&
t->asoc->peer.primary_path == t)
break;
sctp_transport_put(t);
}
return t;
@ -5017,13 +5022,18 @@ struct sctp_transport *sctp_transport_get_idx(struct net *net,
struct rhashtable_iter *iter,
int pos)
{
void *obj = SEQ_START_TOKEN;
struct sctp_transport *t;
while (pos && (obj = sctp_transport_get_next(net, iter)) &&
!IS_ERR(obj))
pos--;
if (!pos)
return SEQ_START_TOKEN;
return obj;
while ((t = sctp_transport_get_next(net, iter)) && !IS_ERR(t)) {
if (!--pos)
break;
sctp_transport_put(t);
}
return t;
}
int sctp_for_each_endpoint(int (*cb)(struct sctp_endpoint *, void *),
@ -5082,8 +5092,6 @@ int sctp_for_each_transport(int (*cb)(struct sctp_transport *, void *),
tsp = sctp_transport_get_idx(net, &hti, *pos + 1);
for (; !IS_ERR_OR_NULL(tsp); tsp = sctp_transport_get_next(net, &hti)) {
if (!sctp_transport_hold(tsp))
continue;
ret = cb(tsp, p);
if (ret)
break;