From 271cd2c1c7d94b5406a0eac1313660bbe5329f61 Mon Sep 17 00:00:00 2001 From: Edward Adam Davis Date: Tue, 3 Sep 2024 23:09:55 +0800 Subject: [PATCH] mptcp: pm: Fix uaf in __timer_delete_sync There are two paths to access mptcp_pm_del_add_timer, result in a race condition: CPU1 CPU2 ==== ==== net_rx_action napi_poll netlink_sendmsg __napi_poll netlink_unicast process_backlog netlink_unicast_kernel __netif_receive_skb genl_rcv __netif_receive_skb_one_core netlink_rcv_skb NF_HOOK genl_rcv_msg ip_local_deliver_finish genl_family_rcv_msg ip_protocol_deliver_rcu genl_family_rcv_msg_doit tcp_v4_rcv mptcp_pm_nl_flush_addrs_doit tcp_v4_do_rcv mptcp_nl_remove_addrs_list tcp_rcv_established mptcp_pm_remove_addrs_and_subflows tcp_data_queue remove_anno_list_by_saddr mptcp_incoming_options mptcp_pm_del_add_timer mptcp_pm_del_add_timer kfree(entry) In remove_anno_list_by_saddr(running on CPU2), after leaving the critical zone protected by "pm.lock", the entry will be released, which leads to the occurrence of uaf in the mptcp_pm_del_add_timer(running on CPU1). Reported-and-tested-by: syzbot+f3a31fb909db9b2a5c4d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d Signed-off-by: Edward Adam Davis --- net/mptcp/pm_netlink.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index a006ce39d41a37..43c7c71f0b81c8 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -343,11 +343,12 @@ mptcp_pm_del_add_timer(struct mptcp_sock *msk, entry = mptcp_lookup_anno_list_by_saddr(msk, addr); if (entry && (!check_id || entry->addr.id == addr->id)) entry->retrans_times = ADD_ADDR_RETRANS_MAX; - spin_unlock_bh(&msk->pm.lock); if (entry && (!check_id || entry->addr.id == addr->id)) sk_stop_timer_sync(sk, &entry->add_timer); + spin_unlock_bh(&msk->pm.lock); + return entry; }