[PATCH 5.9 36/74] gtp: fix an use-before-init in gtp_newlink()

Greg Kroah-Hartman
2020-10-31T11:48:18Z

From: Masahiro Fujiwara <fujiwara.masahiro@gmail.com>

[ Upstream commit 51467431200b91682b89d31317e35dcbca1469ce ]

*_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.

Fixes: 1e3a3abd8b28 ("gtp: make GTP sockets in gtp_newlink optional")
Signed-off-by: Masahiro Fujiwara <fujiwara.masahiro@gmail.com>
Link: https://lore.kernel.org/r/20201027114846.3924-1-fujiwara.masahiro@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/gtp.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -663,10 +663,6 @@ static int gtp_newlink(struct net *src_n

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_n

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_n

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;
}