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 @@ -357,6 +357,18 @@ 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) { @@ -418,8 +430,10 @@ static int sctp_do_bind(struct sock *sk, return -EADDRINUSE;
/* 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. @@ -5115,19 +5129,6 @@ 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; @@ -9402,6 +9403,8 @@ static int sctp_sock_migrate(struct sock return err; }
+ 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. */