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l2tp: hold tunnel while handling genl TUNNEL_GET commands

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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: 309795f4be ("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>
This commit is contained in:
Guillaume Nault
2017-08-25 16:51:43 +02:00
committed by David S. Miller
parent 8c0e421525
commit 4e4b21da3a
1 changed files with 15 additions and 12 deletions
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27
net/l2tp/l2tp_netlink.c
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@@ -444,34 +444,37 @@ static int l2tp_nl_cmd_tunnel_get(struct sk_buff *skb, struct genl_info *info)
if (!info->attrs[L2TP_ATTR_CONN_ID]) { if (!info->attrs[L2TP_ATTR_CONN_ID]) {
ret = -EINVAL; ret = -EINVAL;
goto out; goto err;
} }
tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]); 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); msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
if (!msg) { if (!msg) {
ret = -ENOMEM; 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, ret = l2tp_nl_tunnel_send(msg, info->snd_portid, info->snd_seq,
NLM_F_ACK, tunnel, L2TP_CMD_TUNNEL_GET); NLM_F_ACK, tunnel, L2TP_CMD_TUNNEL_GET);
if (ret < 0) if (ret < 0)
goto err_out; goto err_nlmsg_tunnel;
l2tp_tunnel_dec_refcount(tunnel);
return genlmsg_unicast(net, msg, info->snd_portid); return genlmsg_unicast(net, msg, info->snd_portid);
err_out: err_nlmsg_tunnel:
l2tp_tunnel_dec_refcount(tunnel);
err_nlmsg:
nlmsg_free(msg); nlmsg_free(msg);
err:
out:
return ret; return ret;
} }