linux-kernel - [PATCH 3/4] ipv4: use symbol

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Date:   Thu, 14 May 2020 16:51:00 +0200
From:   Christoph Hellwig <hch@....de>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] ipv4: use symbol_get to access ipip symbols

Instead of going through the ioctl handler from kernel space, use
symbol_get to access the ip_tunnel_ioctl directly.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 net/ipv4/ipmr.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 6bf2a88abe86e..3780ab694c574 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -438,10 +438,9 @@ static bool ipmr_init_vif_indev(const struct net_device *dev)
 
 static struct net_device *ipmr_new_tunnel(struct net *net, struct vifctl *v)
 {
-	mm_segment_t oldfs = get_fs();
+	int (*tunnel_ctl)(struct net_device *, struct ip_tunnel_parm *, int);
 	struct net_device *tunnel_dev, *new_dev;
 	struct ip_tunnel_parm p = { };
-	struct ifreq ifr;
 	int err;
 
 	tunnel_dev = __dev_get_by_name(net, "tunl0");
@@ -454,21 +453,17 @@ static struct net_device *ipmr_new_tunnel(struct net *net, struct vifctl *v)
 	p.iph.ihl = 5;
 	p.iph.protocol = IPPROTO_IPIP;
 	sprintf(p.name, "dvmrp%d", v->vifc_vifi);
-	ifr.ifr_ifru.ifru_data = (__force void __user *)&p;
 
-	if (!tunnel_dev->netdev_ops->ndo_do_ioctl)
-		goto out;
+	tunnel_ctl = symbol_get(ip_tunnel_ioctl);
+	if (!tunnel_ctl)
+		return ERR_PTR(-ENOBUFS);
 
-	set_fs(KERNEL_DS);
-	err = tunnel_dev->netdev_ops->ndo_do_ioctl(tunnel_dev, &ifr,
-			SIOCADDTUNNEL);
-	set_fs(oldfs);
-	if (err)
-		goto out;
+	if (tunnel_ctl(tunnel_dev, &p, SIOCADDTUNNEL))
+		goto out_symbol_put;
 
 	new_dev = __dev_get_by_name(net, p.name);
 	if (!new_dev)
-		goto out;
+		goto out_symbol_put;
 
 	new_dev->flags |= IFF_MULTICAST;
 	if (!ipmr_init_vif_indev(new_dev))
@@ -479,17 +474,18 @@ static struct net_device *ipmr_new_tunnel(struct net *net, struct vifctl *v)
 	err = dev_set_allmulti(new_dev, 1);
 	if (err) {
 		dev_close(new_dev);
-		set_fs(KERNEL_DS);
-		tunnel_dev->netdev_ops->ndo_do_ioctl(tunnel_dev, &ifr,
-				SIOCDELTUNNEL);
-		set_fs(oldfs);
+		tunnel_ctl(tunnel_dev, &p, SIOCDELTUNNEL);
 		dev_put(new_dev);
 		new_dev = ERR_PTR(err);
 	}
+
+	symbol_put(ip_tunnel_ioctl);
 	return new_dev;
 
 out_unregister:
 	unregister_netdevice(new_dev);
+out_symbol_put:
+	symbol_put(ipmr_new_tunnel);
 out:
 	return ERR_PTR(-ENOBUFS);
 }
-- 
2.26.2