4.18-stable review patch. If anyone has any objections, please let me know.
------------------ From: Xin Long <[email protected]> [ Upstream commit bab1be79a5169ac748d8292b20c86d874022d7ba ] 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: 626d16f50f39 ("sctp: export some apis or variables for sctp_diag and reuse some for proc") Reported-by: [email protected] Signed-off-by: Xin Long <[email protected]> Acked-by: Neil Horman <[email protected]> Acked-by: Marcelo Ricardo Leitner <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- net/sctp/proc.c | 4 ---- net/sctp/socket.c | 22 +++++++++++++++------- 2 files changed, 15 insertions(+), 11 deletions(-) --- a/net/sctp/proc.c +++ b/net/sctp/proc.c @@ -260,8 +260,6 @@ static int sctp_assocs_seq_show(struct s } transport = (struct sctp_transport *)v; - if (!sctp_transport_hold(transport)) - return 0; assoc = transport->asoc; epb = &assoc->base; sk = epb->sk; @@ -318,8 +316,6 @@ static int sctp_remaddr_seq_show(struct } 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, --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -4881,9 +4881,14 @@ struct sctp_transport *sctp_transport_ge 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; @@ -4893,13 +4898,18 @@ struct sctp_transport *sctp_transport_ge struct rhashtable_iter *iter, int pos) { - void *obj = SEQ_START_TOKEN; + struct sctp_transport *t; + + if (!pos) + return SEQ_START_TOKEN; - while (pos && (obj = sctp_transport_get_next(net, iter)) && - !IS_ERR(obj)) - pos--; + while ((t = sctp_transport_get_next(net, iter)) && !IS_ERR(t)) { + if (!--pos) + break; + sctp_transport_put(t); + } - return obj; + return t; } int sctp_for_each_endpoint(int (*cb)(struct sctp_endpoint *, void *), @@ -4958,8 +4968,6 @@ again: 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;
