From: Or Cohen orcohen@paloaltonetworks.com
commit b166a20b07382b8bc1dcee2a448715c9c2c81b5b upstream.
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.
The bug is fixed by acquiring addr_wq_lock in sctp_destroy_sock instead of sctp_close.
This addresses CVE-2021-23133.
Reported-by: Or Cohen orcohen@paloaltonetworks.com Reviewed-by: Xin Long lucien.xin@gmail.com Fixes: 610236587600 ("bpf: Add new cgroup attach type to enable sock modifications") Signed-off-by: Or Cohen orcohen@paloaltonetworks.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/socket.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)
--- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -1520,11 +1520,9 @@ static void sctp_close(struct sock *sk,
/* Supposedly, no process has access to the socket, but * the net layers still may. - * Also, sctp_destroy_sock() needs to be called with addr_wq_lock - * held and that should be grabbed before socket lock. */ - spin_lock_bh(&net->sctp.addr_wq_lock); - bh_lock_sock_nested(sk); + local_bh_disable(); + bh_lock_sock(sk);
/* Hold the sock, since sk_common_release() will put sock_put() * and we have just a little more cleanup. @@ -1533,7 +1531,7 @@ static void sctp_close(struct sock *sk, sk_common_release(sk);
bh_unlock_sock(sk); - spin_unlock_bh(&net->sctp.addr_wq_lock); + local_bh_enable();
sock_put(sk);
@@ -4993,9 +4991,6 @@ 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, @@ -5030,7 +5025,9 @@ static void sctp_destroy_sock(struct soc
if (sp->do_auto_asconf) { sp->do_auto_asconf = 0; + spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock); list_del(&sp->auto_asconf_list); + spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock); } sctp_endpoint_free(sp->ep); local_bh_disable();