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Description of problem: Local RedHat Enterprise Linux DoS – RHEL 7.1 Kernel crashes on invalid USB device descriptors (cypress_m8 driver) [local-DoS] Version-Release number of selected component (if applicable): Kernel-Version: 3.10.0-229.20.1.el7.x86_64 How reproducible: always OpenSource Security Ralf Spenneberg Am Bahnhof 3-5 48565 Steinfurt info Date: November 12th, 2015 Authors: Sergej Schumilo, Hendrik Schwartke, Ralf Spenneberg CVE: not yet assigned CVSS: 4.9 (AV:L/AC:L/Au:N/C:N/I:N/A:C) Title: Local RedHat Enterprise Linux DoS – RHEL 7.1 Kernel crashes on invalid USB device descriptors (cypress_m8 driver) [local-DoS] Severity: Critical. The Kernel panics. A reboot is required. Ease of Exploitation: Trivial Vulnerability type: Wrong input validation Products: RHEL 7.1 including all updates Kernel-Version: 3.10.0-229.20.1.el7.x86_64 (for debugging-purposes we used the CentOS Kernel kernel-debuginfo-3.10.0-229.14.1.el7) Abstract The Kernel 3.10.0-229.20.1.el7.x86_64 crashes when presented a buggy USB device which requires the cypress_m8 driver. Detailed product description We confirmed the bug on the following system: RHEL 7.1 Kernel = 3.10.0-229.20.1.el7.x86_64 Further products or kernel versions have not been tested. How reproducible: Always Actual results: Kernel crashes Description: The bug was found using the USB-fuzzing framework vUSBf from Sergej Schumilo (github.com/schumilo) using the following device descriptor: ######### PAYLOAD 1 ######### [*] Device-Descriptor bLength: 0x12 bDescriptorType: 0x1 bcdUSB: 0x200 bDeviceClass: 0x3 bDeviceSubClass: 0x0 bDeviceProtocol: 0x0 bMaxPacketSize: 0x40 idVendor: 0x4b4 idProduct: 0x5500 bcdDevice: 0x100 iManufacturer: 0x1 iProduct: 0x2 iSerialNumbers: 0x3 bNumConfigurations: 0x1 This is the configuration descriptor containing only one interrupt-endpoint-descriptor (IN-direction). The cypress_m8 driver assumes that there will be at least two endpoint-descriptors configured for interrupt-transfer and each used for one direction. Since there is no sanity check, it is possible that the kernel tries to dereference a null-pointer. This results in a crash of the system. **** $ nm cypress_m8.ko.debug | grep cypress_generic_port_probe 00000000000008d0 t cypress_generic_port_probe $ addr2line -e cypress_m8.ko.debug 0x9D0 /usr/src/debug/kernel-3.10.0-229.14.1.el7/linux-3.10.0-229.14.1.el7.x86_64/drivers/usb/serial/cypress_m8.c:488 **** **** CentOS-Kernel linux-3.10.0-229.14.1.el7 (drivers/usb/serial/cypress_m8.c) ... 482 if (interval > 0) { 483 priv->write_urb_interval = interval; 484 priv->read_urb_interval = interval; 485 dev_dbg(&port->dev, "%s - read & write intervals forced to %d\n", 486 __func__, interval); 487 } else { 488 priv->write_urb_interval = port->interrupt_out_urb->interval; /* possible null-pointer dereference */ 489 priv->read_urb_interval = port->interrupt_in_urb->interval; /* possible null-pointer dereference */ 490 dev_dbg(&port->dev, "%s - intervals: read=%d write=%d\n", 491 __func__, priv->read_urb_interval, 492 priv->write_urb_interval); 493 } ... **** [*] Configuration-Descriptor bLength: 0x9 bDescriptorType: 0x2 wTotalLength: 0x27 bNumInterfaces: 0x1 bConfigurationValue: 0x1 iConfiguration: 0x0 bmAttributes: 0x0 bMaxPower: 0x31 [*] Interface-Descriptor bLength: 0x9 bDescriptorType: 0x4 bInterfaceNumber: 0x0 bAlternateSetting: 0x0 bNumEndpoints: 0x3 bInterfaceClass: 0x0 bInterfaceSubClass: 0x0 bInterfaceProtocol: 0x0 [*] Endpoint-Descriptor bLength: 0x7 bDescriptorType: 0x5 bEndpointAddress: 0x81 <-- IN-Direction bmAttribut: 0x3 <-- Interrupt-Transfer wMaxPacketSize: 0x404 bInterval: 0xc [*] Endpoint-Descriptor bLength: 0x7 bDescriptorType: 0x5 bEndpointAddress: 0x1 <-- OUT-Direction bmAttribut: 0x2 <-- Bulk-Transfer wMaxPacketSize: 0x4 bInterval: 0xc [*] Endpoint-Descriptor bLength: 0x7 bDescriptorType: 0x5 bEndpointAddress: 0x82 <-- IN-Direction bmAttribut: 0x1 <-- Bulk-Transfer wMaxPacketSize: 0x4 bInterval: 0xc Proof of Concept: 1) The bug can be reproduced using USB-fuzzing framework vUSBf from Sergej Schumilo (github.com/schumilo). The attached vUSBf-obj file contains the payload. Please let us know if you would like to use the Facedancer board. In such case, we could also provide a patched version of vUSBf which allows to reproduce vUSBf-Payloads using the Facedancer board. 2) For a proof of concept we are providing also an Arduino firmware file. Just flash it on Arduino Leonardo and plug it into any RHEL machine. The Arduino will emulate the defective USB device. avrdude -v -p ATMEGA32u4 -c avr109 -P /dev/ttyACM0 -b 57600 -U flash:w:binary.hex The file binary.hex has been attached to this bug report. To prevent automated sending of payloads, use a jumper to connect port D3 and 5V! Severity and Ease of Exploitation The security weakness can be easily exploited. Using our Arduino firmware only physical access to the system is required. Additional info: Stacktrace, vUSBf-Payload, Arduino-Firmware attached. Please assign a CVE for this issue since this is a local DoS of the targeted system. CVSS 4.9 (AV:L/AC:L/Au:N/C:N/I:N/A:C)
Created attachment 1096269 [details] vUSBf Payload
Created attachment 1096270 [details] Stacktrace
Created attachment 1096271 [details] Arduino firmware demonstrating the bug
Public via: http://seclists.org/bugtraq/2016/Mar/55
CVEID was requested at: http://seclists.org/oss-sec/2016/q1/604
CVE-2016-3137 was assigned to this flaw, please, use it in the related communications, see http://seclists.org/oss-sec/2016/q1/621.
Patch was sent upstream for CVE-2016-3137, many thanks to Oliver Neukum: http://marc.info/?l=linux-usb&m=145813816318926&w=2
Thank you for reporting this flaw. The Product Security has rated this flaw as having low security impact (bz#1316996), so the patch is currently not planned to be added to the RHEL source trees. If accepted to the upstream, the patch may get to the RHEL trees later at the next USB subsystem code rebase.