From: Taehee Yoo <ap420073@gmail.com>
Date: Wed, 11 Dec 2019 08:23:17 +0000
Subject: gtp: fix wrong condition in gtp_genl_dump_pdp()
Git-commit: 94a6d9fb88df43f92d943c32b84ce398d50bf49f
Patch-mainline: 5.5-rc3
References: networking-stable-20_01_01

gtp_genl_dump_pdp() is ->dumpit() callback of GTP module and it is used
to dump pdp contexts. it would be re-executed because of dump packet size.

If dump packet size is too big, it saves current dump pointer
(gtp interface pointer, bucket, TID value) then it restarts dump from
last pointer.
Current GTP code allows adding zero TID pdp context but dump code
ignores zero TID value. So, last dump pointer will not be found.

In addition, this patch adds missing rcu_read_lock() in
gtp_genl_dump_pdp().

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/gtp.c |   36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -42,7 +42,6 @@ struct pdp_ctx {
 	struct hlist_node	hlist_addr;
 
 	union {
-		u64		tid;
 		struct {
 			u64	tid;
 			u16	flow;
@@ -1224,43 +1223,46 @@ static int gtp_genl_dump_pdp(struct sk_b
 				struct netlink_callback *cb)
 {
 	struct gtp_dev *last_gtp = (struct gtp_dev *)cb->args[2], *gtp;
+	int i, j, bucket = cb->args[0], skip = cb->args[1];
 	struct net *net = sock_net(skb->sk);
-	struct gtp_net *gn = net_generic(net, gtp_net_id);
-	unsigned long tid = cb->args[1];
-	int i, k = cb->args[0], ret;
 	struct pdp_ctx *pctx;
+	struct gtp_net *gn;
+
+	gn = net_generic(net, gtp_net_id);
 
 	if (cb->args[4])
 		return 0;
 
+	rcu_read_lock();
 	list_for_each_entry_rcu(gtp, &gn->gtp_dev_list, list) {
 		if (last_gtp && last_gtp != gtp)
 			continue;
 		else
 			last_gtp = NULL;
 
-		for (i = k; i < gtp->hash_size; i++) {
-			hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid) {
-				if (tid && tid != pctx->u.tid)
-					continue;
-				else
-					tid = 0;
-
-				ret = gtp_genl_fill_info(skb,
-							 NETLINK_CB(cb->skb).portid,
-							 cb->nlh->nlmsg_seq,
-							 cb->nlh->nlmsg_type, pctx);
-				if (ret < 0) {
+		for (i = bucket; i < gtp->hash_size; i++) {
+			j = 0;
+			hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i],
+						 hlist_tid) {
+				if (j >= skip &&
+				    gtp_genl_fill_info(skb,
+					    NETLINK_CB(cb->skb).portid,
+					    cb->nlh->nlmsg_seq,
+					    cb->nlh->nlmsg_type, pctx)) {
 					cb->args[0] = i;
-					cb->args[1] = pctx->u.tid;
+					cb->args[1] = j;
 					cb->args[2] = (unsigned long)gtp;
 					goto out;
 				}
+				j++;
 			}
+			skip = 0;
 		}
+		bucket = 0;
 	}
 	cb->args[4] = 1;
 out:
+	rcu_read_unlock();
 	return skb->len;
 }