From: Wei Yongjun weiyongjun1@huawei.com
[ Upstream commit 46ef5b89ec0ecf290d74c4aee844f063933c4da4 ]
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: dafabb6590cb ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv6/ip6_gre.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
--- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1562,17 +1562,18 @@ static void ip6gre_destroy_tunnels(struc 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(st return 0;
err_reg_dev: - free_netdev(ign->fb_tunnel_dev); + free_netdev(ndev); err_alloc_dev: return err; }