Re: [PATCH ver.2] gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump_pdp()

[kovalev@altlinux.org]

14.02.2024 19:49, Pablo Neira Ayuso wrote:
> On Wed, Feb 14, 2024 at 07:27:33PM +0300, kovalev@altlinux.org wrote:
>> From: Vasiliy Kovalev <kovalev@altlinux.org>
>>
>> The gtp_net_ops pernet operations structure for the subsystem must be
>> registered before registering the generic netlink family.
> Thanks for finding a remedy for this.
>
> If your fix is correct, (I didn't test your patch yet) then maybe this
> needs to be fixed in a few more spots in the tree?
>
> net/devlink/core.c-static int __init devlink_init(void)
> net/devlink/core.c-{
> net/devlink/core.c-     int err;
> net/devlink/core.c-
> net/devlink/core.c-     err = genl_register_family(&devlink_nl_family);
> net/devlink/core.c-     if (err)
> net/devlink/core.c-             goto out;
> net/devlink/core.c:     err = register_pernet_subsys(&devlink_pernet_ops);
> net/devlink/core.c-     if (err)
>
> net/handshake/netlink.c-        ret = genl_register_family(&handshake_nl_family);
> net/handshake/netlink.c-        if (ret) {
> net/handshake/netlink.c-                pr_warn("handshake: netlink registration failed (%d)\n", ret);
> net/handshake/netlink.c-                handshake_req_hash_destroy();
> net/handshake/netlink.c-                return ret;
> net/handshake/netlink.c-        }
> net/handshake/netlink.c-
> net/handshake/netlink.c-        /*
> net/handshake/netlink.c-         * ORDER: register_pernet_subsys must be done last.
> net/handshake/netlink.c-         *
> net/handshake/netlink.c-         *      If initialization does not make it past pernet_subsys
> net/handshake/netlink.c-         *      registration, then handshake_net_id will remain 0. That
> net/handshake/netlink.c-         *      shunts the handshake consumer API to return ENOTSUPP
> net/handshake/netlink.c-         *      to prevent it from dereferencing something that hasn't
> net/handshake/netlink.c-         *      been allocated.
> net/handshake/netlink.c-         */
> net/handshake/netlink.c:        ret = register_pernet_subsys(&handshake_genl_net_ops);
>
> net/ipv4/tcp_metrics.c: ret = register_pernet_subsys(&tcp_net_metrics_ops);
> net/ipv4/tcp_metrics.c- if (ret < 0)
> net/ipv4/tcp_metrics.c-         panic("Could not register tcp_net_metrics_ops\n");
> net/ipv4/tcp_metrics.c-
> net/ipv4/tcp_metrics.c- ret = genl_register_family(&tcp_metrics_nl_family);
> net/ipv4/tcp_metrics.c- if (ret < 0)
> net/ipv4/tcp_metrics.c-         panic("Could not register tcp_metrics generic netlink\n");
> net/ipv4/tcp_metrics.c-}
>
> net/ipv6/ioam6.c-int __init ioam6_init(void)
> net/ipv6/ioam6.c-{
> net/ipv6/ioam6.c:       int err = register_pernet_subsys(&ioam6_net_ops);
> net/ipv6/ioam6.c-       if (err)
> net/ipv6/ioam6.c-               goto out;
> net/ipv6/ioam6.c-
> net/ipv6/ioam6.c-       err = genl_register_family(&ioam6_genl_family);
> net/ipv6/ioam6.c-       if (err)
> net/ipv6/ioam6.c-               goto out_unregister_pernet_subsys;
>
> net/ipv6/seg6.c-        err = genl_register_family(&seg6_genl_family);
> net/ipv6/seg6.c-        if (err)
> net/ipv6/seg6.c-                goto out;
> net/ipv6/seg6.c-
> net/ipv6/seg6.c:        err = register_pernet_subsys(&ip6_segments_ops);
> net/ipv6/seg6.c-        if (err)
> net/ipv6/seg6.c-                goto out_unregister_genl;
>
> net/netlink/genetlink.c-        err = genl_register_family(&genl_ctrl);
> net/netlink/genetlink.c-        if (err < 0)
> net/netlink/genetlink.c-                goto problem;
> net/netlink/genetlink.c-
> net/netlink/genetlink.c:        err = register_pernet_subsys(&genl_pernet_ops);
> net/netlink/genetlink.c-        if (err)
> net/netlink/genetlink.c-                goto problem;

Most likely, judging by the backtrace, the bug is the same [1]:

Call Trace:
  <TASK>
  genl_dumpit+0x119/0x220 net/netlink/genetlink.c:1025
  netlink_dump+0x588/0xca0 net/netlink/af_netlink.c:2264
  __netlink_dump_start+0x6d0/0x9c0 net/netlink/af_netlink.c:2370
  genl_family_rcv_msg_dumpit+0x1e1/0x2d0 net/netlink/genetlink.c:1074
  genl_family_rcv_msg net/netlink/genetlink.c:1190 [inline]
  genl_rcv_msg+0x470/0x800 net/netlink/genetlink.c:1208
  netlink_rcv_skb+0x16b/0x440 net/netlink/af_netlink.c:2543
  genl_rcv+0x28/0x40 net/netlink/genetlink.c:1217
  netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
  netlink_unicast+0x53b/0x810 net/netlink/af_netlink.c:1367
  netlink_sendmsg+0x8b7/0xd70 net/netlink/af_netlink.c:1908
  sock_sendmsg_nosec net/socket.c:730 [inline]
  __sock_sendmsg+0xd5/0x180 net/socket.c:745
  ____sys_sendmsg+0x6ac/0x940 net/socket.c:2584
  ___sys_sendmsg+0x135/0x1d0 net/socket.c:2638
  __sys_sendmsg+0x117/0x1e0 net/socket.c:2667
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xd3/0x250 arch/x86/entry/common.c:83
  entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f35d567cda9

[1] https://lore.kernel.org/all/0000000000007549a6060f99544d@google.com/T/


-- 
Regards,
Vasiliy Kovalev