diff options
| author | James Chapman <jchapman@katalix.com> | 2024-07-29 16:38:10 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2024-07-31 09:25:13 +0100 |
| commit | 24256415d18695b46da06c93135f5b51c548b950 (patch) | |
| tree | 2eeeb81ce18d163d866a80599d080e637d160942 /net/l2tp/l2tp_netlink.c | |
| parent | c5cbaef992d6420d8bcebea1b1fcc23302a67c57 (diff) | |
l2tp: prevent possible tunnel refcount underflow
When a session is created, it sets a backpointer to its tunnel. When
the session refcount drops to 0, l2tp_session_free drops the tunnel
refcount if session->tunnel is non-NULL. However, session->tunnel is
set in l2tp_session_create, before the tunnel refcount is incremented
by l2tp_session_register, which leaves a small window where
session->tunnel is non-NULL when the tunnel refcount hasn't been
bumped.
Moving the assignment to l2tp_session_register is trivial but
l2tp_session_create calls l2tp_session_set_header_len which uses
session->tunnel to get the tunnel's encap. Add an encap arg to
l2tp_session_set_header_len to avoid using session->tunnel.
If l2tpv3 sessions have colliding IDs, it is possible for
l2tp_v3_session_get to race with l2tp_session_register and fetch a
session which doesn't yet have session->tunnel set. Add a check for
this case.
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp/l2tp_netlink.c')
| -rw-r--r-- | net/l2tp/l2tp_netlink.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index d105030520f9..fc43ecbd128c 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -692,8 +692,10 @@ static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *inf session->recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]); if (info->attrs[L2TP_ATTR_SEND_SEQ]) { + struct l2tp_tunnel *tunnel = session->tunnel; + session->send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]); - l2tp_session_set_header_len(session, session->tunnel->version); + l2tp_session_set_header_len(session, tunnel->version, tunnel->encap); } if (info->attrs[L2TP_ATTR_LNS_MODE]) |