From: Xin Long <lucien.xin@xxxxxxxxx>
commit 34e5b01186858b36c4d7c87e1a025071e8e2401f upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sctp/socket.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -367,6 +367,18 @@ static struct sctp_af *sctp_sockaddr_af(
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)
{
@@ -429,8 +441,10 @@ static int sctp_do_bind(struct sock *sk,
}
/* 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.
@@ -4262,19 +4276,6 @@ 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,
- &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;
@@ -7817,6 +7818,8 @@ static void sctp_sock_migrate(struct soc
sctp_bind_addr_dup(&newsp->ep->base.bind_addr,
&oldsp->ep->base.bind_addr, GFP_KERNEL);
+ 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.
*/
