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Description of problem: Local RedHat Enterprise Linux DoS – RHEL 7.1 Kernel crashes on invalid USB device descriptors (ati_remote2 driver bug1) [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 (ati_remote2 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 ati_remote2 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: 0xff bDeviceSubClass: 0x0 bDeviceProtocol: 0x0 bMaxPacketSize: 0x40 idVendor: 0x471 idProduct: 0x602 bcdDevice: 0x100 iManufacturer: 0x1 iProduct: 0x2 iSerialNumbers: 0x3 bNumConfigurations: 0x1 This is the configuration descriptor containing only one interface descriptor. The ati_remote2 driver assumes that there will be at least two interface-descriptors with associated endpoint-descriptors. Since the ati_remote2 driver is expecting a second interface descriptor, the driver tries to dereference a null-pointer. This results in a crash of the system. The null-pointer dereference happens in usb_driver_claim_interface() because the ati_remote2 driver passes in the second parameter a null-pointer: **** $ nm ati_remote2.ko.debug | grep ati_remote2_probe 0000000000001300 t ati_remote2_probe $ addr2line -e ati_remote2.ko.debug 1399 /usr/src/debug/kernel-3.10.0-229.14.1.el7/linux-3.10.0-229.14.1.el7.x86_64/drivers/input/misc/ati_remote2.c:825 **** **** CentOS-Kernel linux-3.10.0-229.14.1.el7 (drivers/input/misc/ati_remote2.c) ... 820 ar2->intf[0] = interface; 821 ar2->ep[0] = &alt->endpoint[0].desc; 822 823 ar2->intf[1] = usb_ifnum_to_if(udev, 1); /* <-- usb_ifnum_to_if returns a null-pointer if there is only one interface configured */ 824 r = usb_driver_claim_interface(&ati_remote2_driver, ar2->intf[1], ar2); /* the second parameter is obviously a null-pointer which crashes the system */ 825 if (r) 826 goto fail1; 827 alt = ar2->intf[1]->cur_altsetting; ... **** [*] 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: 0x0 bInterfaceClass: 0x0 bInterfaceSubClass: 0x0 bInterfaceProtocol: 0x0 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, additional vUSBf-Descriptorfile 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 1096258 [details] vUSBf Payload This vUSBf-Payload requires a file named ati_remote2_bug1.txt located in vUSBf/dev_desc. This file is also attached to this bug-report (* see vUSBf-Descriptorfile *).
Created attachment 1096259 [details] Modified vUSBf descriptor file
Created attachment 1096260 [details] Stacktrace
Created attachment 1096261 [details] Arduino firmware demonstrating the bug
CVE-2016-2185 which is Red Hat's private CVE ID was assigned to this security flaw. Please, use it in the public communications regarding this flaw, thank you.
public via: http://seclists.org/bugtraq/2016/Mar/90
patch posted upstream (linux-usb@ and linux-input@ lists): http://marc.info/?l=linux-usb&m=145874840924378&w=2 | http://article.gmane.org/gmane.linux.usb.general/139169 | http://www.spinics.net/lists/linux-usb/msg138107.html http://marc.info/?l=linux-input&m=145874841024379&w=2 | http://www.spinics.net/lists/linux-input/msg43818.html
Thank you for reporting this flaw. The Product Security has rated this flaw as having low security impact (bz#1317014), 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.