Hi Greg,
[disclaimer, just commenting as a bystander, noticing this failed
apply]
On Wed, May 12, 2021 at 02:11:21PM +0200, gregkh@xxxxxxxxxxxxxxxxxxx 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@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From 34e5b01186858b36c4d7c87e1a025071e8e2401f Mon Sep 17 00:00:00 2001
> From: Xin Long <lucien.xin@xxxxxxxxx>
> 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:
> 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@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
>
> 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
