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gtp: fix an use-after-free in ipv4_pdp_find()
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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 torvalds#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 torvalds#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: 459aa66 ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
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@TaeheeYoo @intel-lab-lkp
TaeheeYoo authored and intel-lab-lkp committed Dec 11, 2019
1 parent 2cd35f7 commit 383a501
Showing 1 changed file with 17 additions and 17 deletions.
34 changes: 17 additions & 17 deletions drivers/net/gtp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down Expand Up @@ -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;
Expand All @@ -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);
}
Expand Down Expand Up @@ -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)
{
Expand Down

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