From: Or Cohen orcohen@paloaltonetworks.com

mainline inclusion from mainline-v5.12-rc8 commit b166a20b07382b8bc1dcee2a448715c9c2c81b5b category: bugfix bugzilla: NA CVE: CVE-2021-23133

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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: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Yue Haibing yuehaibing@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- net/sctp/socket.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 733c3f448008..addfc8feaef5 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -1571,11 +1571,9 @@ static void sctp_close(struct sock *sk, long timeout)

/* 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. @@ -1584,7 +1582,7 @@ static void sctp_close(struct sock *sk, long timeout) sk_common_release(sk);

bh_unlock_sock(sk); - spin_unlock_bh(&net->sctp.addr_wq_lock); + local_bh_enable();

sock_put(sk);

@@ -4779,9 +4777,6 @@ static int sctp_init_sock(struct sock *sk) 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, @@ -4816,7 +4811,9 @@ static void sctp_destroy_sock(struct sock *sk)

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();