Hi Greg,
[disclaimer, just commenting as a bystander, noticing this failed apply]
On Wed, May 12, 2021 at 02:11:21PM +0200, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 5.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
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: [PATCH] sctp: delay auto_asconf init until binding the first addr
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:
- In sctp_accept, if sctp_sock_migrate fails.
- 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
diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 76a388b5021c..40f9f6c4a0a1 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -357,6 +357,18 @@ static struct sctp_af *sctp_sockaddr_af(struct sctp_sock *opt, 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, union sctp_addr *addr, int len) 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. @@ -4993,19 +5007,6 @@ 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,&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; @@ -9401,6 +9402,8 @@ static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk, 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.
Before applying this patch one needs to revert first b166a20b07382b8bc1dcee2a448715c9c2c81b5b .
So first apply 01bfe5e8e428 ("Revert "net/sctp: fix race condition in sctp_destroy_sock"") and then apply 34e5b0118685 ("sctp: delay auto_asconf init until binding the first addr").
Regards, Salvatore