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l2tp: hold tunnel while handling genl TUNNEL_GET commands 

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: 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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Guillaume Nault 2017-08-25 16:51:43 +02:00 committed by syphyr
parent 5902818298
commit 07a1dadcf4
1 changed files with 15 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
net/l2tp/l2tp_netlink.c
View File

@ -343,34 +343,37 @@ static int l2tp_nl_cmd_tunnel_get(struct sk_buff *skb, struct genl_info *info)
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);
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;
}