[PATCH v3] gtp: fix an use-before-init in gtp_newlink()

*_pdp_find() from gtp_encap_recv() would trigger a crash when a peer sends GTP packets while creating new GTP device. RIP: 0010:gtp1_pdp_find.isra.0+0x68/0x90 [gtp] <SNIP> Call Trace: <IRQ> gtp_encap_recv+0xc2/0x2e0 [gtp] ? gtp1_pdp_find.isra.0+0x90/0x90 [gtp] udp_queue_rcv_one_skb+0x1fe/0x530 udp_queue_rcv_skb+0x40/0x1b0 udp_unicast_rcv_skb.isra.0+0x78/0x90 __udp4_lib_rcv+0x5af/0xc70 udp_rcv+0x1a/0x20 ip_protocol_deliver_rcu+0xc5/0x1b0 ip_local_deliver_finish+0x48/0x50 ip_local_deliver+0xe5/0xf0 ? ip_protocol_deliver_rcu+0x1b0/0x1b0 gtp_encap_enable() should be called after gtp_hastable_new() otherwise *_pdp_find() will access the uninitialized hash table. v2: - Leave out_hashtable: label for clarity (Jakub). - Fix code and comment styles. Fixes: 1e3a3abd8b28 ("gtp: make GTP sockets in gtp_newlink optional") Signed-off-by: Masahiro Fujiwara &lt;fujiwara.masahiro(a)gmail.com&gt; --- v3: - Fix goto err label. drivers/net/gtp.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 8e47d0112e5d..10f910f8cbe5 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -663,10 +663,6 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev, gtp = netdev_priv(dev); - err = gtp_encap_enable(gtp, data); - if (err < 0) - return err; - if (!data[IFLA_GTP_PDP_HASHSIZE]) { hashsize = 1024; } else { @@ -677,12 +673,16 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev, err = gtp_hashtable_new(gtp, hashsize); if (err < 0) - goto out_encap; + return err; + + err = gtp_encap_enable(gtp, data); + if (err < 0) + goto out_hashtable; err = register_netdevice(dev); if (err < 0) { netdev_dbg(dev, "failed to register new netdev %d\n", err); - goto out_hashtable; + goto out_encap; } gn = net_generic(dev_net(dev), gtp_net_id); @@ -693,11 +693,11 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev, return 0; +out_encap: + gtp_encap_disable(gtp); out_hashtable: kfree(gtp->addr_hash); kfree(gtp->tid_hash); -out_encap: - gtp_encap_disable(gtp); return err; } -- 2.24.3