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net/sctp: fix race condition in sctp_destroy_sock

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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: 6102365876 ("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>
This commit is contained in:
Or Cohen 2021-04-13 21:10:31 +03:00 committed by David S. Miller
parent ca09bf7bb1
commit b166a20b07
1 changed files with 5 additions and 8 deletions
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13
net/sctp/socket.c
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@ -1520,11 +1520,9 @@ 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.
@ -1533,7 +1531,7 @@ 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);
@ -4993,9 +4991,6 @@ 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,
@ -5030,7 +5025,9 @@ 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();