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l2tp: reject creation of non-PPP sessions on L2TPv2 tunnels

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The /proc/net/pppol2tp handlers (pppol2tp_seq_*()) iterate over all
L2TPv2 tunnels, and rightfully expect that only PPP sessions can be
found there. However, l2tp_netlink accepts creating Ethernet sessions
regardless of the underlying tunnel version.

This confuses pppol2tp_seq_session_show(), which expects that
l2tp_session_priv() returns a pppol2tp_session structure. When the
session is an Ethernet pseudo-wire, a struct l2tp_eth_sess is returned
instead. This leads to invalid memory access when
pppol2tp_session_get_sock() later tries to dereference ps->sk.

Fixes: d9e31d17ce ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Guillaume Nault 2018-06-15 15:39:17 +02:00 committed by David S. Miller
parent eab9a2d5f3
commit de9bada5d3
1 changed files with 6 additions and 0 deletions
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6
net/l2tp/l2tp_netlink.c
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@ -553,6 +553,12 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
goto out_tunnel;
}
/* L2TPv2 only accepts PPP pseudo-wires */
if (tunnel->version == 2 && cfg.pw_type != L2TP_PWTYPE_PPP) {
ret = -EPROTONOSUPPORT;
goto out_tunnel;
}
if (tunnel->version > 2) {
if (info->attrs[L2TP_ATTR_DATA_SEQ])
cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);