The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 94dc550a5062030569d4aa76e10e50c8fc001930 Mon Sep 17 00:00:00 2001

From: Taehee Yoo ap420073@gmail.com Date: Wed, 11 Dec 2019 08:23:34 +0000 Subject: [PATCH] gtp: fix an use-after-free in ipv4_pdp_find()

ipv4_pdp_find() is called in TX packet path of GTP. ipv4_pdp_find() internally uses gtp->tid_hash to lookup pdp context. In the current code, gtp->tid_hash and gtp->addr_hash are freed by ->dellink(), which is gtp_dellink(). But gtp_dellink() would be called while packets are processing. So, gtp_dellink() should not free gtp->tid_hash and gtp->addr_hash. Instead, dev->priv_destructor() would be used because this callback is called after all packet processing safely.

Test commands: ip link add veth1 type veth peer name veth2 ip a a 172.0.0.1/24 dev veth1 ip link set veth1 up ip a a 172.99.0.1/32 dev lo

gtp-link add gtp1 &

gtp-tunnel add gtp1 v1 200 100 172.99.0.2 172.0.0.2 ip r a 172.99.0.2/32 dev gtp1 ip link set gtp1 mtu 1500

ip netns add ns2 ip link set veth2 netns ns2 ip netns exec ns2 ip a a 172.0.0.2/24 dev veth2 ip netns exec ns2 ip link set veth2 up ip netns exec ns2 ip a a 172.99.0.2/32 dev lo ip netns exec ns2 ip link set lo up

ip netns exec ns2 gtp-link add gtp2 & ip netns exec ns2 gtp-tunnel add gtp2 v1 100 200 172.99.0.1 172.0.0.1 ip netns exec ns2 ip r a 172.99.0.1/32 dev gtp2 ip netns exec ns2 ip link set gtp2 mtu 1500

hping3 172.99.0.2 -2 --flood & ip link del gtp1

Splat looks like: [ 72.568081][ T1195] BUG: KASAN: use-after-free in ipv4_pdp_find.isra.12+0x130/0x170 [gtp] [ 72.568916][ T1195] Read of size 8 at addr ffff8880b9a35d28 by task hping3/1195 [ 72.569631][ T1195] [ 72.569861][ T1195] CPU: 2 PID: 1195 Comm: hping3 Not tainted 5.5.0-rc1 #199 [ 72.570547][ T1195] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [ 72.571438][ T1195] Call Trace: [ 72.571764][ T1195] dump_stack+0x96/0xdb [ 72.572171][ T1195] ? ipv4_pdp_find.isra.12+0x130/0x170 [gtp] [ 72.572761][ T1195] print_address_description.constprop.5+0x1be/0x360 [ 72.573400][ T1195] ? ipv4_pdp_find.isra.12+0x130/0x170 [gtp] [ 72.573971][ T1195] ? ipv4_pdp_find.isra.12+0x130/0x170 [gtp] [ 72.574544][ T1195] __kasan_report+0x12a/0x16f [ 72.575014][ T1195] ? ipv4_pdp_find.isra.12+0x130/0x170 [gtp] [ 72.575593][ T1195] kasan_report+0xe/0x20 [ 72.576004][ T1195] ipv4_pdp_find.isra.12+0x130/0x170 [gtp] [ 72.576577][ T1195] gtp_build_skb_ip4+0x199/0x1420 [gtp] [ ... ] [ 72.647671][ T1195] BUG: unable to handle page fault for address: ffff8880b9a35d28 [ 72.648512][ T1195] #PF: supervisor read access in kernel mode [ 72.649158][ T1195] #PF: error_code(0x0000) - not-present page [ 72.649849][ T1195] PGD a6c01067 P4D a6c01067 PUD 11fb07067 PMD 11f939067 PTE 800fffff465ca060 [ 72.652958][ T1195] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI [ 72.653834][ T1195] CPU: 2 PID: 1195 Comm: hping3 Tainted: G B 5.5.0-rc1 #199 [ 72.668062][ T1195] RIP: 0010:ipv4_pdp_find.isra.12+0x86/0x170 [gtp] [ ... ] [ 72.679168][ T1195] Call Trace: [ 72.679603][ T1195] gtp_build_skb_ip4+0x199/0x1420 [gtp] [ 72.681915][ T1195] ? ipv4_pdp_find.isra.12+0x170/0x170 [gtp] [ 72.682513][ T1195] ? lock_acquire+0x164/0x3b0 [ 72.682966][ T1195] ? gtp_dev_xmit+0x35e/0x890 [gtp] [ 72.683481][ T1195] gtp_dev_xmit+0x3c2/0x890 [gtp] [ ... ]

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)") Signed-off-by: Taehee Yoo ap420073@gmail.com Signed-off-by: Jakub Kicinski jakub.kicinski@netronome.com

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index a010e0a11c33..5450b1099c6d 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -640,9 +640,16 @@ static void gtp_link_setup(struct net_device *dev) }

static int gtp_hashtable_new(struct gtp_dev *gtp, int hsize); -static void gtp_hashtable_free(struct gtp_dev *gtp); static int gtp_encap_enable(struct gtp_dev *gtp, struct nlattr *data[]);

+static void gtp_destructor(struct net_device *dev) +{ + struct gtp_dev *gtp = netdev_priv(dev); + + kfree(gtp->addr_hash); + kfree(gtp->tid_hash); +} + static int gtp_newlink(struct net *src_net, struct net_device *dev, struct nlattr *tb[], struct nlattr *data[], struct netlink_ext_ack *extack) @@ -677,13 +684,15 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,

gn = net_generic(dev_net(dev), gtp_net_id); list_add_rcu(&gtp->list, &gn->gtp_dev_list); + dev->priv_destructor = gtp_destructor;

netdev_dbg(dev, "registered new GTP interface\n");

return 0;

out_hashtable: - gtp_hashtable_free(gtp); + kfree(gtp->addr_hash); + kfree(gtp->tid_hash); out_encap: gtp_encap_disable(gtp); return err; @@ -692,8 +701,13 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev, static void gtp_dellink(struct net_device *dev, struct list_head *head) { struct gtp_dev *gtp = netdev_priv(dev); + struct pdp_ctx *pctx; + int i; + + for (i = 0; i < gtp->hash_size; i++) + hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid) + pdp_context_delete(pctx);

- gtp_hashtable_free(gtp); list_del_rcu(&gtp->list); unregister_netdevice_queue(dev, head); } @@ -771,20 +785,6 @@ static int gtp_hashtable_new(struct gtp_dev *gtp, int hsize) return -ENOMEM; }

-static void gtp_hashtable_free(struct gtp_dev *gtp) -{ - struct pdp_ctx *pctx; - int i; - - for (i = 0; i < gtp->hash_size; i++) - hlist_for_each_entry_rcu(pctx, &gtp->tid_hash[i], hlist_tid) - pdp_context_delete(pctx); - - synchronize_rcu(); - kfree(gtp->addr_hash); - kfree(gtp->tid_hash); -} - static struct sock *gtp_encap_enable_socket(int fd, int type, struct gtp_dev *gtp) {