[PATCH 5.19 280/717] sctp: handle the error returned from sctp_auth_asoc_init_active_key

Greg Kroah-Hartman
2022-10-22T08:02:42Z

From: Xin Long <lucien.xin@gmail.com>

[ 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>
---
net/sctp/auth.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index db6b7373d16c..34964145514e 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -863,12 +863,17 @@ 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;
}

@@ -902,8 +907,13 @@ 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;

--
2.35.1