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l2tp: initialise session's refcount before making it reachable

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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>
This commit is contained in:
Guillaume Nault 2020-05-22 00:39:25 +01:00 committed by Greg Kroah-Hartman
parent d4504d1eba
commit 11a083724b
1 changed files with 2 additions and 4 deletions
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6
net/l2tp/l2tp_core.c
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@ -1847,6 +1847,8 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
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);
@ -1854,10 +1856,6 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
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 */