| From 34e5b01186858b36c4d7c87e1a025071e8e2401f Mon Sep 17 00:00:00 2001 |
| From: Xin Long <lucien.xin@gmail.com> |
| Date: Mon, 3 May 2021 05:11:42 +0800 |
| Subject: sctp: delay auto_asconf init until binding the first addr |
| |
| From: Xin Long <lucien.xin@gmail.com> |
| |
| commit 34e5b01186858b36c4d7c87e1a025071e8e2401f upstream. |
| |
| As Or Cohen described: |
| |
| If sctp_destroy_sock is called without sock_net(sk)->sctp.addr_wq_lock |
| held and sp->do_auto_asconf is true, then an element is removed |
| from the auto_asconf_splist without any proper locking. |
| |
| This can happen in the following functions: |
| 1. In sctp_accept, if sctp_sock_migrate fails. |
| 2. In inet_create or inet6_create, if there is a bpf program |
| attached to BPF_CGROUP_INET_SOCK_CREATE which denies |
| creation of the sctp socket. |
| |
| This patch is to fix it by moving the auto_asconf init out of |
| sctp_init_sock(), by which inet_create()/inet6_create() won't |
| need to operate it in sctp_destroy_sock() when calling |
| sk_common_release(). |
| |
| It also makes more sense to do auto_asconf init while binding the |
| first addr, as auto_asconf actually requires an ANY addr bind, |
| see it in sctp_addr_wq_timeout_handler(). |
| |
| This addresses CVE-2021-23133. |
| |
| Fixes: 610236587600 ("bpf: Add new cgroup attach type to enable sock modifications") |
| Reported-by: Or Cohen <orcohen@paloaltonetworks.com> |
| Signed-off-by: Xin Long <lucien.xin@gmail.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/sctp/socket.c | 31 +++++++++++++++++-------------- |
| 1 file changed, 17 insertions(+), 14 deletions(-) |
| |
| --- a/net/sctp/socket.c |
| +++ b/net/sctp/socket.c |
| @@ -367,6 +367,18 @@ static struct sctp_af *sctp_sockaddr_af( |
| return af; |
| } |
| |
| +static void sctp_auto_asconf_init(struct sctp_sock *sp) |
| +{ |
| + struct net *net = sock_net(&sp->inet.sk); |
| + |
| + if (net->sctp.default_auto_asconf) { |
| + spin_lock(&net->sctp.addr_wq_lock); |
| + list_add_tail(&sp->auto_asconf_list, &net->sctp.auto_asconf_splist); |
| + spin_unlock(&net->sctp.addr_wq_lock); |
| + sp->do_auto_asconf = 1; |
| + } |
| +} |
| + |
| /* Bind a local address either to an endpoint or to an association. */ |
| static int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len) |
| { |
| @@ -429,8 +441,10 @@ static int sctp_do_bind(struct sock *sk, |
| } |
| |
| /* Refresh ephemeral port. */ |
| - if (!bp->port) |
| + if (!bp->port) { |
| bp->port = inet_sk(sk)->inet_num; |
| + sctp_auto_asconf_init(sp); |
| + } |
| |
| /* Add the address to the bind address list. |
| * Use GFP_ATOMIC since BHs will be disabled. |
| @@ -4262,19 +4276,6 @@ static int sctp_init_sock(struct sock *s |
| sk_sockets_allocated_inc(sk); |
| sock_prot_inuse_add(net, sk->sk_prot, 1); |
| |
| - /* Nothing can fail after this block, otherwise |
| - * sctp_destroy_sock() will be called without addr_wq_lock held |
| - */ |
| - if (net->sctp.default_auto_asconf) { |
| - spin_lock(&sock_net(sk)->sctp.addr_wq_lock); |
| - list_add_tail(&sp->auto_asconf_list, |
| - &net->sctp.auto_asconf_splist); |
| - sp->do_auto_asconf = 1; |
| - spin_unlock(&sock_net(sk)->sctp.addr_wq_lock); |
| - } else { |
| - sp->do_auto_asconf = 0; |
| - } |
| - |
| local_bh_enable(); |
| |
| return 0; |
| @@ -7817,6 +7818,8 @@ static void sctp_sock_migrate(struct soc |
| sctp_bind_addr_dup(&newsp->ep->base.bind_addr, |
| &oldsp->ep->base.bind_addr, GFP_KERNEL); |
| |
| + sctp_auto_asconf_init(newsp); |
| + |
| /* Move any messages in the old socket's receive queue that are for the |
| * peeled off association to the new socket's receive queue. |
| */ |