Commit 382ff447 authored Sep 28, 2022 by Xin Long Committed by Greg Kroah-Hartman Oct 26, 2022

sctp: handle the error returned from sctp_auth_asoc_init_active_key



[ Upstream commit 022152aaebe116a25c39818a07e175a8cd3c1e11 ]

When it returns an error from sctp_auth_asoc_init_active_key(), the
active_key is actually not updated. The old sh_key will be freeed
while it's still used as active key in asoc. Then an use-after-free
will be triggered when sending patckets, as found by syzbot:

  sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
  sctp_set_owner_w net/sctp/socket.c:132 [inline]
  sctp_sendmsg_to_asoc+0xbd5/0x1a20 net/sctp/socket.c:1863
  sctp_sendmsg+0x1053/0x1d50 net/sctp/socket.c:2025
  inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:819
  sock_sendmsg_nosec net/socket.c:714 [inline]
  sock_sendmsg+0xcf/0x120 net/socket.c:734

This patch is to fix it by not replacing the sh_key when it returns
errors from sctp_auth_asoc_init_active_key() in sctp_auth_set_key().
For sctp_auth_set_active_key(), old active_key_id will be set back
to asoc->active_key_id when the same thing happens.

Fixes: 58acd1009226 ("sctp: update active_key for asoc when old key is being replaced")
Reported-by:  <syzbot+a236dd8e9622ed8954a3@syzkaller.appspotmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 466ed722

net/sctp/auth.c

+14 −4

Original line number	Diff line number	Diff line
		@@ -869,12 +869,17 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
		}

		list_del_init(&shkey->key_list);
		sctp_auth_shkey_release(shkey);
		list_add(&cur_key->key_list, sh_keys);

		if (asoc && asoc->active_key_id == auth_key->sca_keynumber)
		sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
		if (asoc && asoc->active_key_id == auth_key->sca_keynumber &&
		sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL)) {
		list_del_init(&cur_key->key_list);
		sctp_auth_shkey_release(cur_key);
		list_add(&shkey->key_list, sh_keys);
		return -ENOMEM;
		}

		sctp_auth_shkey_release(shkey);
		return 0;
		}

		@@ -908,8 +913,13 @@ int sctp_auth_set_active_key(struct sctp_endpoint *ep,
		return -EINVAL;

		if (asoc) {
		__u16 active_key_id = asoc->active_key_id;

		asoc->active_key_id = key_id;
		sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
		if (sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL)) {
		asoc->active_key_id = active_key_id;
		return -ENOMEM;
		}
		} else
		ep->active_key_id = key_id;