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Subject[PATCH 4.4 48/65] l2tp: initialise sessions refcount before making it reachable
Date
From: Guillaume Nault <g.nault@alphalink.fr>

commit 9ee369a405c57613d7c83a3967780c3e30c52ecc upstream.

Sessions must be fully initialised before calling
l2tp_session_add_to_tunnel(). Otherwise, there's a short time frame
where partially initialised sessions can be accessed by external users.

Backporting Notes

l2tp_core.c: moving code that had been converted from atomic to
refcount_t by an earlier change (which isn't being included in this
patch series).

Fixes: dbdbc73b4478 ("l2tp: fix duplicate session creation")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/l2tp/l2tp_core.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1853,6 +1853,8 @@ struct l2tp_session *l2tp_session_create

l2tp_session_set_header_len(session, tunnel->version);

+ l2tp_session_inc_refcount(session);
+
err = l2tp_session_add_to_tunnel(tunnel, session);
if (err) {
kfree(session);
@@ -1860,10 +1862,6 @@ struct l2tp_session *l2tp_session_create
return ERR_PTR(err);
}

- /* Bump the reference count. The session context is deleted
- * only when this drops to zero.
- */
- l2tp_session_inc_refcount(session);
l2tp_tunnel_inc_refcount(tunnel);

/* Ensure tunnel socket isn't deleted */

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