netdev - [PATCH net-next] l2tp: consistent reference counting in procfs and debufs

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Date:   Wed, 25 Apr 2018 19:54:14 +0200
From:   Guillaume Nault <g.nault@...halink.fr>
To:     netdev@...r.kernel.org
Cc:     James Chapman <jchapman@...alix.com>
Subject: [PATCH net-next] l2tp: consistent reference counting in procfs and
 debufs

The 'pppol2tp' procfs and 'l2tp/tunnels' debugfs files handle reference
counting of sessions differently than for tunnels.

For consistency, use the same mechanism for handling both sessions and
tunnels. That is, drop the reference on the previous session just
before looking up the next one (rather than in .show()). If necessary
(if dump stops before *_next_session() returns NULL), drop the last
reference in .stop().

Signed-off-by: Guillaume Nault <g.nault@...halink.fr>
---
 net/l2tp/l2tp_debugfs.c | 20 +++++++++++++-------
 net/l2tp/l2tp_ppp.c     | 21 +++++++++++++--------
 2 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
index 7f1e842ef05a..e87686f7d63c 100644
--- a/net/l2tp/l2tp_debugfs.c
+++ b/net/l2tp/l2tp_debugfs.c
@@ -57,6 +57,10 @@ static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd)
 
 static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
 {
+	/* Drop reference taken during previous invocation */
+	if (pd->session)
+		l2tp_session_dec_refcount(pd->session);
+
 	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
 	pd->session_idx++;
 
@@ -105,11 +109,16 @@ static void l2tp_dfs_seq_stop(struct seq_file *p, void *v)
 	if (!pd || pd == SEQ_START_TOKEN)
 		return;
 
-	/* Drop reference taken by last invocation of l2tp_dfs_next_tunnel() */
+	/* Drop reference taken by last invocation of l2tp_dfs_next_session()
+	 * or l2tp_dfs_next_tunnel().
+	 */
+	if (pd->session) {
+		l2tp_session_dec_refcount(pd->session);
+		pd->session = NULL;
+	}
 	if (pd->tunnel) {
 		l2tp_tunnel_dec_refcount(pd->tunnel);
 		pd->tunnel = NULL;
-		pd->session = NULL;
 	}
 }
 
@@ -250,13 +259,10 @@ static int l2tp_dfs_seq_show(struct seq_file *m, void *v)
 		goto out;
 	}
 
-	/* Show the tunnel or session context */
-	if (!pd->session) {
+	if (!pd->session)
 		l2tp_dfs_seq_tunnel_show(m, pd->tunnel);
-	} else {
+	else
 		l2tp_dfs_seq_session_show(m, pd->session);
-		l2tp_session_dec_refcount(pd->session);
-	}
 
 out:
 	return 0;
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 1fd9e145076a..f951c768dcf2 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -1576,6 +1576,10 @@ static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd)
 
 static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
 {
+	/* Drop reference taken during previous invocation */
+	if (pd->session)
+		l2tp_session_dec_refcount(pd->session);
+
 	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
 	pd->session_idx++;
 
@@ -1624,11 +1628,16 @@ static void pppol2tp_seq_stop(struct seq_file *p, void *v)
 	if (!pd || pd == SEQ_START_TOKEN)
 		return;
 
-	/* Drop reference taken by last invocation of pppol2tp_next_tunnel() */
+	/* Drop reference taken by last invocation of pppol2tp_next_session()
+	 * or pppol2tp_next_tunnel().
+	 */
+	if (pd->session) {
+		l2tp_session_dec_refcount(pd->session);
+		pd->session = NULL;
+	}
 	if (pd->tunnel) {
 		l2tp_tunnel_dec_refcount(pd->tunnel);
 		pd->tunnel = NULL;
-		pd->session = NULL;
 	}
 }
 
@@ -1723,14 +1732,10 @@ static int pppol2tp_seq_show(struct seq_file *m, void *v)
 		goto out;
 	}
 
-	/* Show the tunnel or session context.
-	 */
-	if (!pd->session) {
+	if (!pd->session)
 		pppol2tp_seq_tunnel_show(m, pd->tunnel);
-	} else {
+	else
 		pppol2tp_seq_session_show(m, pd->session);
-		l2tp_session_dec_refcount(pd->session);
-	}
 
 out:
 	return 0;
-- 
2.17.0