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ip6_gre: fix null-ptr-deref in ip6gre_init_net()

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KASAN report null-ptr-deref error when register_netdev() failed:

KASAN: null-ptr-deref in range [0x00000000000003c0-0x00000000000003c7]
CPU: 2 PID: 422 Comm: ip Not tainted 5.8.0-rc4+ #12
Call Trace:
 ip6gre_init_net+0x4ab/0x580
 ? ip6gre_tunnel_uninit+0x3f0/0x3f0
 ops_init+0xa8/0x3c0
 setup_net+0x2de/0x7e0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 ? ops_init+0x3c0/0x3c0
 ? kasan_unpoison_shadow+0x33/0x40
 ? __kasan_kmalloc.constprop.0+0xc2/0xd0
 copy_net_ns+0x27d/0x530
 create_new_namespaces+0x382/0xa30
 unshare_nsproxy_namespaces+0xa1/0x1d0
 ksys_unshare+0x39c/0x780
 ? walk_process_tree+0x2a0/0x2a0
 ? trace_hardirqs_on+0x4a/0x1b0
 ? _raw_spin_unlock_irq+0x1f/0x30
 ? syscall_trace_enter+0x1a7/0x330
 ? do_syscall_64+0x1c/0xa0
 __x64_sys_unshare+0x2d/0x40
 do_syscall_64+0x56/0xa0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

ip6gre_tunnel_uninit() has set 'ign->fb_tunnel_dev' to NULL, later
access to ign->fb_tunnel_dev cause null-ptr-deref. Fix it by saving
'ign->fb_tunnel_dev' to local variable ndev.

Fixes: dafabb6590 ("ip6_gre: fix use-after-free in ip6gre_tunnel_lookup()")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Yongjun 2020-07-13 23:59:50 +08:00 committed by David S. Miller
parent e0484010ec
commit 46ef5b89ec
1 changed files with 6 additions and 5 deletions
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11
net/ipv6/ip6_gre.c
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@ -1562,17 +1562,18 @@ static void ip6gre_destroy_tunnels(struct net *net, struct list_head *head)
static int __net_init ip6gre_init_net(struct net *net)
{
struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
struct net_device *ndev;
int err;
if (!net_has_fallback_tunnels(net))
return 0;
ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6gre0",
NET_NAME_UNKNOWN,
ip6gre_tunnel_setup);
if (!ign->fb_tunnel_dev) {
ndev = alloc_netdev(sizeof(struct ip6_tnl), "ip6gre0",
NET_NAME_UNKNOWN, ip6gre_tunnel_setup);
if (!ndev) {
err = -ENOMEM;
goto err_alloc_dev;
}
ign->fb_tunnel_dev = ndev;
dev_net_set(ign->fb_tunnel_dev, net);
/* FB netdevice is special: we have one, and only one per netns.
* Allowing to move it to another netns is clearly unsafe.
@ -1592,7 +1593,7 @@ static int __net_init ip6gre_init_net(struct net *net)
return 0;
err_reg_dev:
free_netdev(ign->fb_tunnel_dev);
free_netdev(ndev);
err_alloc_dev:
return err;
}