Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+eba992608adf3d796bcc@syzkaller.appspotmail.com,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Johan Hedberg <johan.hedberg@intel.com>
Subject: [PATCH 5.4 22/90] Bluetooth: Fix race condition in hci_release_sock()
Date:   Mon,  3 Feb 2020 16:19:25 +0000
Message-Id: <20200203161920.591354269@linuxfoundation.org>
In-Reply-To: <20200203161917.612554987@linuxfoundation.org>
References: <20200203161917.612554987@linuxfoundation.org>
User-Agent: quilt/0.66
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Dan Carpenter <dan.carpenter@oracle.com>

commit 11eb85ec42dc8c7a7ec519b90ccf2eeae9409de8 upstream.

Syzbot managed to trigger a use after free "KASAN: use-after-free Write
in hci_sock_bind".  I have reviewed the code manually and one possibly
cause I have found is that we are not holding lock_sock(sk) when we do
the hci_dev_put(hdev) in hci_sock_release().  My theory is that the bind
and the release are racing against each other which results in this use
after free.

Reported-by: syzbot+eba992608adf3d796bcc@syzkaller.appspotmail.com
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/bluetooth/hci_sock.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -831,6 +831,8 @@ static int hci_sock_release(struct socke
 	if (!sk)
 		return 0;
 
+	lock_sock(sk);
+
 	switch (hci_pi(sk)->channel) {
 	case HCI_CHANNEL_MONITOR:
 		atomic_dec(&monitor_promisc);
@@ -878,6 +880,7 @@ static int hci_sock_release(struct socke
 	skb_queue_purge(&sk->sk_receive_queue);
 	skb_queue_purge(&sk->sk_write_queue);
 
+	release_sock(sk);
 	sock_put(sk);
 	return 0;
 }