linux-kernel - [PATCH 5.4 065/108] sctp: update active_key for asoc when old key is being replaced

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Date:   Mon, 26 Jul 2021 17:39:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+b774577370208727d12b@...kaller.appspotmail.com,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 065/108] sctp: update active_key for asoc when old key is being replaced

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

[ Upstream commit 58acd10092268831e49de279446c314727101292 ]

syzbot reported a call trace:

  BUG: KASAN: use-after-free in sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
  Call Trace:
   sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
   sctp_set_owner_w net/sctp/socket.c:131 [inline]
   sctp_sendmsg_to_asoc+0x152e/0x2180 net/sctp/socket.c:1865
   sctp_sendmsg+0x103b/0x1d30 net/sctp/socket.c:2027
   inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
   sock_sendmsg_nosec net/socket.c:703 [inline]
   sock_sendmsg+0xcf/0x120 net/socket.c:723

This is an use-after-free issue caused by not updating asoc->shkey after
it was replaced in the key list asoc->endpoint_shared_keys, and the old
key was freed.

This patch is to fix by also updating active_key for asoc when old key is
being replaced with a new one. Note that this issue doesn't exist in
sctp_auth_del_key_id(), as it's not allowed to delete the active_key
from the asoc.

Fixes: 1b1e0bc99474 ("sctp: add refcnt support for sh_key")
Reported-by: syzbot+b774577370208727d12b@...kaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sctp/auth.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 1d898ee4018c..7eced1e523a5 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -866,6 +866,8 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
 	if (replace) {
 		list_del_init(&shkey->key_list);
 		sctp_auth_shkey_release(shkey);
+		if (asoc && asoc->active_key_id == auth_key->sca_keynumber)
+			sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
 	}
 	list_add(&cur_key->key_list, sh_keys);
 
-- 
2.30.2