On Wed, May 12, 2021 at 02:40:38PM +0200, Salvatore Bonaccorso wrote:
> Hi,
>
> On Wed, May 12, 2021 at 02:35:16PM +0200, Salvatore Bonaccorso wrote:
> > 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").
>
> Forgot to mention: At least for back to 5.10.y this should be the
> problem for the patch not applying. Not checked for older series
> further.
Thank you, that worked!
greg k-h
