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Subject[PATCH 4.9 41/64] l2tp: hold tunnel used while creating sessions with netlink
Date
From: Guillaume Nault <g.nault@alphalink.fr>

commit e702c1204eb57788ef189c839c8c779368267d70 upstream.

Use l2tp_tunnel_get() to retrieve tunnel, so that it can't go away on
us. Otherwise l2tp_tunnel_destruct() might release the last reference
count concurrently, thus freeing the tunnel while we're using it.

Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
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_netlink.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -510,8 +510,9 @@ static int l2tp_nl_cmd_session_create(st
ret = -EINVAL;
goto out;
}
+
tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
- tunnel = l2tp_tunnel_find(net, tunnel_id);
+ tunnel = l2tp_tunnel_get(net, tunnel_id);
if (!tunnel) {
ret = -ENODEV;
goto out;
@@ -519,24 +520,24 @@ static int l2tp_nl_cmd_session_create(st

if (!info->attrs[L2TP_ATTR_SESSION_ID]) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}
session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);

if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}
peer_session_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_SESSION_ID]);

if (!info->attrs[L2TP_ATTR_PW_TYPE]) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}
cfg.pw_type = nla_get_u16(info->attrs[L2TP_ATTR_PW_TYPE]);
if (cfg.pw_type >= __L2TP_PWTYPE_MAX) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}

if (tunnel->version > 2) {
@@ -555,7 +556,7 @@ static int l2tp_nl_cmd_session_create(st
u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);
if (len > 8) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}
cfg.cookie_len = len;
memcpy(&cfg.cookie[0], nla_data(info->attrs[L2TP_ATTR_COOKIE]), len);
@@ -564,7 +565,7 @@ static int l2tp_nl_cmd_session_create(st
u16 len = nla_len(info->attrs[L2TP_ATTR_PEER_COOKIE]);
if (len > 8) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}
cfg.peer_cookie_len = len;
memcpy(&cfg.peer_cookie[0], nla_data(info->attrs[L2TP_ATTR_PEER_COOKIE]), len);
@@ -607,7 +608,7 @@ static int l2tp_nl_cmd_session_create(st
if ((l2tp_nl_cmd_ops[cfg.pw_type] == NULL) ||
(l2tp_nl_cmd_ops[cfg.pw_type]->session_create == NULL)) {
ret = -EPROTONOSUPPORT;
- goto out;
+ goto out_tunnel;
}

/* Check that pseudowire-specific params are present */
@@ -617,7 +618,7 @@ static int l2tp_nl_cmd_session_create(st
case L2TP_PWTYPE_ETH_VLAN:
if (!info->attrs[L2TP_ATTR_VLAN_ID]) {
ret = -EINVAL;
- goto out;
+ goto out_tunnel;
}
break;
case L2TP_PWTYPE_ETH:
@@ -645,6 +646,8 @@ static int l2tp_nl_cmd_session_create(st
}
}

+out_tunnel:
+ l2tp_tunnel_dec_refcount(tunnel);
out:
return ret;
}

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