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Subject[PATCH 4.9 40/64] l2tp: hold tunnel while handling genl TUNNEL_GET commands
Date
From: Guillaume Nault <g.nault@alphalink.fr>

commit 4e4b21da3acc68a7ea55f850cacc13706b7480e9 upstream.

Use l2tp_tunnel_get() instead of l2tp_tunnel_find() so that we get
a reference on the tunnel, preventing l2tp_tunnel_destruct() from
freeing it from under us.

Also move l2tp_tunnel_get() below nlmsg_new() so that we only take
the reference when needed.

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 | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)

--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -436,34 +436,37 @@ static int l2tp_nl_cmd_tunnel_get(struct

if (!info->attrs[L2TP_ATTR_CONN_ID]) {
ret = -EINVAL;
- goto out;
+ goto err;
}

tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);

- tunnel = l2tp_tunnel_find(net, tunnel_id);
- if (tunnel == NULL) {
- ret = -ENODEV;
- goto out;
- }
-
msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
if (!msg) {
ret = -ENOMEM;
- goto out;
+ goto err;
+ }
+
+ tunnel = l2tp_tunnel_get(net, tunnel_id);
+ if (!tunnel) {
+ ret = -ENODEV;
+ goto err_nlmsg;
}

ret = l2tp_nl_tunnel_send(msg, info->snd_portid, info->snd_seq,
NLM_F_ACK, tunnel, L2TP_CMD_TUNNEL_GET);
if (ret < 0)
- goto err_out;
+ goto err_nlmsg_tunnel;
+
+ l2tp_tunnel_dec_refcount(tunnel);

return genlmsg_unicast(net, msg, info->snd_portid);

-err_out:
+err_nlmsg_tunnel:
+ l2tp_tunnel_dec_refcount(tunnel);
+err_nlmsg:
nlmsg_free(msg);
-
-out:
+err:
return ret;
}


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