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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Jiri Slaby <jslaby@suse.com>,
	Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: [PATCH 4.14 26/39] tty: link tty and port before configuring it as console
Date: Tue, 14 Jan 2020 11:02:00 +0100
Message-ID: <20200114094344.699176547@linuxfoundation.org> (raw)
In-Reply-To: <20200114094336.210038037@linuxfoundation.org>

From: Sudip Mukherjee <sudipm.mukherjee@gmail.com>

commit fb2b90014d782d80d7ebf663e50f96d8c507a73c upstream.

There seems to be a race condition in tty drivers and I could see on
many boot cycles a NULL pointer dereference as tty_init_dev() tries to
do 'tty->port->itty = tty' even though tty->port is NULL.
'tty->port' will be set by the driver and if the driver has not yet done
it before we open the tty device we can get to this situation. By adding
some extra debug prints, I noticed that:

6.650130: uart_add_one_port
6.663849: register_console
6.664846: tty_open
6.674391: tty_init_dev
6.675456: tty_port_link_device

uart_add_one_port() registers the console, as soon as it registers, the
userspace tries to use it and that leads to tty_open() but
uart_add_one_port() has not yet done tty_port_link_device() and so
tty->port is not yet configured when control reaches tty_init_dev().

Further look into the code and tty_port_link_device() is done by
uart_add_one_port(). After registering the console uart_add_one_port()
will call tty_port_register_device_attr_serdev() and
tty_port_link_device() is called from this.

Call add tty_port_link_device() before uart_configure_port() is done and
add a check in tty_port_link_device() so that it only links the port if
it has not been done yet.

Suggested-by: Jiri Slaby <jslaby@suse.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191212131602.29504-1-sudipm.mukherjee@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/serial_core.c |    1 +
 drivers/tty/tty_port.c           |    3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2810,6 +2810,7 @@ int uart_add_one_port(struct uart_driver
 	if (uport->cons && uport->dev)
 		of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
 
+	tty_port_link_device(port, drv->tty_driver, uport->line);
 	uart_configure_port(drv, state, uport);
 
 	port->console = uart_console(uport);
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -88,7 +88,8 @@ void tty_port_link_device(struct tty_por
 {
 	if (WARN_ON(index >= driver->num))
 		return;
-	driver->ports[index] = port;
+	if (!driver->ports[index])
+		driver->ports[index] = port;
 }
 EXPORT_SYMBOL_GPL(tty_port_link_device);
 



  parent reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 10:01 [PATCH 4.14 00/39] 4.14.165-stable review Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 01/39] chardev: Avoid potential use-after-free in chrdev_open() Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 02/39] usb: chipidea: host: Disable port power only if previously enabled Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 03/39] ALSA: usb-audio: Apply the sample rate quirk for Bose Companion 5 Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 04/39] ALSA: hda/realtek - Add new codec supported for ALCS1200A Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 05/39] ALSA: hda/realtek - Set EAPD control to default for ALC222 Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 06/39] kernel/trace: Fix do not unregister tracepoints when register sched_migrate_task fail Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 07/39] tracing: Have stack tracer compile when MCOUNT_INSN_SIZE is not defined Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 08/39] HID: Fix slab-out-of-bounds read in hid_field_extract Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 09/39] HID: uhid: Fix returning EPOLLOUT from uhid_char_poll Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 10/39] can: gs_usb: gs_usb_probe(): use descriptors of current altsetting Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 11/39] can: mscan: mscan_rx_poll(): fix rx path lockup when returning from polling to irq mode Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 12/39] can: can_dropped_invalid_skb(): ensure an initialized headroom in outgoing CAN sk_buffs Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 13/39] gpiolib: acpi: Turn dmi_system_id table into a generic quirk table Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 14/39] gpiolib: acpi: Add honor_wakeup module-option + quirk mechanism Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 15/39] staging: vt6656: set usb_set_intfdata on driver fail Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 16/39] USB: serial: option: add ZLP support for 0x1bc7/0x9010 Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 17/39] usb: musb: fix idling for suspend after disconnect interrupt Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 18/39] usb: musb: Disable pullup at init Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 19/39] usb: musb: dma: Correct parameter passed to IRQ handler Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 20/39] staging: comedi: adv_pci1710: fix AI channels 16-31 for PCI-1713 Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 21/39] HID: hid-input: clear unmapped usages Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 22/39] Input: add safety guards to input_set_keycode() Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 23/39] drm/fb-helper: Round up bits_per_pixel if possible Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 24/39] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ Greg Kroah-Hartman
2020-01-14 10:01 ` [PATCH 4.14 25/39] staging: rtl8188eu: Add device code for TP-Link TL-WN727N v5.21 Greg Kroah-Hartman
2020-01-14 10:02 ` Greg Kroah-Hartman [this message]
2020-01-14 10:02 ` [PATCH 4.14 27/39] tty: always relink the port Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 28/39] mwifiex: fix possible heap overflow in mwifiex_process_country_ie() Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 29/39] mwifiex: pcie: Fix memory leak in mwifiex_pcie_alloc_cmdrsp_buf Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 30/39] scsi: bfa: release allocated memory in case of error Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 31/39] rtl8xxxu: prevent leaking urb Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 32/39] ath10k: fix memory leak Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 33/39] arm64: cpufeature: Avoid warnings due to unused symbols Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 34/39] HID: hiddev: fix mess in hiddev_open() Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 35/39] USB: Fix: Dont skip endpoint descriptors with maxpacket=0 Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 36/39] phy: cpcap-usb: Fix error path when no host driver is loaded Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 37/39] phy: cpcap-usb: Fix flakey host idling and enumerating of devices Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 38/39] netfilter: arp_tables: init netns pointer in xt_tgchk_param struct Greg Kroah-Hartman
2020-01-14 10:02 ` [PATCH 4.14 39/39] netfilter: ipset: avoid null deref when IPSET_ATTR_LINENO is present Greg Kroah-Hartman
2020-01-14 15:02 ` [PATCH 4.14 00/39] 4.14.165-stable review Jon Hunter
2020-01-14 18:15 ` Guenter Roeck
2020-01-14 20:27 ` shuah
2020-01-15  2:08 ` Daniel Díaz

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