sctp: return next obj by passing pos + 1 into sctp_transport_get_idx

In sctp_for_each_transport, pos is used to save how many objs it has
dumped. Now it gets the last obj by sctp_transport_get_idx, then gets
the next obj by sctp_transport_get_next.

The issue is that in the meanwhile if some objs in transport hashtable
are removed and the objs nums are less than pos, sctp_transport_get_idx
would return NULL and hti.walker.tbl is NULL as well. At this moment
it should stop hti, instead of continue getting the next obj. Or it
would cause a NULL pointer dereference in sctp_transport_get_next.

This patch is to pass pos + 1 into sctp_transport_get_idx to get the
next obj directly, even if pos > objs nums, it would return NULL and
stop hti.

Fixes: 626d16f50f39 ("sctp: export some apis or variables for sctp_diag and reuse some for proc")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 30aa0a529215ae54e43bdcb54a6e1870761996c3..3a8318e518f1c10a375dc3ff6ba6596579bb85a1 100644 (file)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4666,9 +4666,8 @@ int sctp_for_each_transport(int (*cb)(struct sctp_transport *, void *),
        if (err)
                return err;
 
-       sctp_transport_get_idx(net, &hti, pos);
-       obj = sctp_transport_get_next(net, &hti);
-       for (; obj && !IS_ERR(obj); obj = sctp_transport_get_next(net, &hti)) {
+       obj = sctp_transport_get_idx(net, &hti, pos + 1);
+       for (; !IS_ERR_OR_NULL(obj); obj = sctp_transport_get_next(net, &hti)) {
                struct sctp_transport *transport = obj;
 
                if (!sctp_transport_hold(transport))