linux-kernel - Re: [PATCH v3] Bluetooth: hci_uart: check for missing tty operations

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Message-Id: <F6BBC244-B565-4651-9EDD-8C1B8621392F@holtmann.org>
Date:   Tue, 30 Jul 2019 11:34:11 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Vladis Dronov <vdronov@...hat.com>
Cc:     Balakrishna Godavarthi <bgodavar@...eaurora.org>,
        Frederic Danis <frederic.danis@...ux.intel.com>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Loic Poulain <loic.poulain@...el.com>,
        Suraj Sumangala <suraj@...eros.com>, syzkaller@...glegroups.com
Subject: Re: [PATCH v3] Bluetooth: hci_uart: check for missing tty operations

Hi Vladis,

> Certain ttys operations (pty_unix98_ops) lack tiocmget() and tiocmset()
> functions which are called by the certain HCI UART protocols (hci_ath,
> hci_bcm, hci_intel, hci_mrvl, hci_qca) via hci_uart_set_flow_control()
> or directly. This leads to an execution at NULL and can be triggered by
> an unprivileged user. Fix this by adding a helper function and a check
> for the missing tty operations in the protocols code.
> 
> This fixes CVE-2019-10207. The Fixes: lines list commits where calls to
> tiocm[gs]et() or hci_uart_set_flow_control() were added to the HCI UART
> protocols.
> 
> Link: https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
> Reported-by: syzbot+79337b501d6aa974d0f6@...kaller.appspotmail.com
> Cc: stable@...r.kernel.org # v2.6.36+
> Fixes: b3190df62861 ("Bluetooth: Support for Atheros AR300x serial chip")
> Fixes: 118612fb9165 ("Bluetooth: hci_bcm: Add suspend/resume PM functions")
> Fixes: ff2895592f0f ("Bluetooth: hci_intel: Add Intel baudrate configuration support")
> Fixes: 162f812f23ba ("Bluetooth: hci_uart: Add Marvell support")
> Fixes: fa9ad876b8e0 ("Bluetooth: hci_qca: Add support for Qualcomm Bluetooth chip wcn3990")
> Signed-off-by: Vladis Dronov <vdronov@...hat.com>
> ---
> 
> out-of-commit-message-note:
> 
> it is possible that a HCI UART protocol uses serial device's
> operations and not a tty ones. i made hci_uart_has_flow_control() to
> check this also, hence the name. serial device's code checks if
> the needed operations are present itself.
> 
> i believe, hci_h5 does not need this check, as it uses serial device
> functions only (as of now):
> 
>    serdev_device_set_flow_control(h5->hu->serdev, false);
>    serdev_device_set_baudrate(h5->hu->serdev, 115200);
> 
> drivers/bluetooth/hci_ath.c   | 3 +++
> drivers/bluetooth/hci_bcm.c   | 3 +++
> drivers/bluetooth/hci_intel.c | 3 +++
> drivers/bluetooth/hci_ldisc.c | 7 +++++++
> drivers/bluetooth/hci_mrvl.c  | 3 +++
> drivers/bluetooth/hci_qca.c   | 3 +++
> drivers/bluetooth/hci_uart.h  | 1 +
> 7 files changed, 23 insertions(+)

I changed the hci_uart_has_flow_control function into using more readable separate checks and then send the patch directly to Linus.

Regards

Marcel