Red Hat Bugzilla – Bug 1283377
CVE-2016-3139 Local RedHat Enterprise Linux DoS – RHEL 7.1 Kernel crashes on invalid USB device descriptors (wacom driver) [local-DoS] Bug2
Last modified: 2016-11-08 11:02:52 EST
Description of problem: Local RedHat Enterprise Linux DoS – RHEL 7.1 Kernel crashes on invalid USB device descriptors (wacom driver) [local-DoS] Bug2 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@os-s.net 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 (wacom 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 wacom 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: 0x56a idProduct: 0x90 bcdDevice: 0x100 iManufacturer: 0x1 iProduct: 0x2 iSerialNumbers: 0x3 bNumConfigurations: 0x1 This is the configuration descriptor containing the malicious value for bNumEndpoints causing the crash. A zero value for bNumEndpoints crashes the system. [*] 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 [*] Endpoint-Descriptor bLength: 0x7 bDescriptorType: 0x5 bEndpointAddress: 0x81 bmAttribut: 0x3 wMaxPacketSize: 0x404 bInterval: 0xc [*] Endpoint-Descriptor bLength: 0x7 bDescriptorType: 0x5 bEndpointAddress: 0x1 bmAttribut: 0x2 wMaxPacketSize: 0x4 bInterval: 0xc [*] Endpoint-Descriptor bLength: 0x7 bDescriptorType: 0x5 bEndpointAddress: 0x82 bmAttribut: 0x2 wMaxPacketSize: 0x4 bInterval: 0xc The wacom driver assumes that there will be at least one endpoint-descriptor. If the interface-descriptor contains a zero-value for bNumEndpoints or no endpoint-descriptor is provided, the driver tries to dereference a null-pointer and the kernel crashes: **** $ nm wacom.ko.debug | grep wacom_probe 00000000000054a0 t wacom_probe $ addr2line -e wacom.ko.debug 0x5756 /usr/src/debug/kernel-3.10.0-229.14.1.el7/linux-3.10.0-229.14.1.el7.x86_64/drivers/input/tablet/wacom_sys.c:599 **** **** CentOS-Kernel linux-3.10.0-229.14.1.el7 (drivers/input/tablet/wacom-sys.c) ... 597 error = usb_get_extra_descriptor(interface, HID_DEVICET_HID, &hid_desc); 598 if (error) { 599 error = usb_get_extra_descriptor(&interface->endpoint[0], /* possible null-pointer dereference */ 600 HID_DEVICET_REPORT, &hid_desc); ... **** 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 1096290 [details] vUSBf Payload
Created attachment 1096291 [details] Stacktrace
Created attachment 1096293 [details] Arduino firmware demonstrating the bug
This bz and bz1283375 are related, as both are caused by the same issue, zero endpoints, while the driver expects at least one endpoint to be present. The bug is that the driver does not check that at least one endpoint is present and accesses the first endpoint causing null-ptr deref. Crashes in these 2 bzs are in the different places because of the different execution paths. [ drivers/input/tablet/wacom_sys.c ] static int wacom_probe(struct usb_interface *intf, const struct usb_device_id *id) { ... endpoint = &intf->cur_altsetting->endpoint[0].desc; <<< This is NULL ... error = wacom_retrieve_hid_descriptor(intf, features); static int wacom_retrieve_hid_descriptor(struct usb_interface *intf ... { ... struct usb_host_interface *interface = intf->cur_altsetting; ... error = usb_get_extra_descriptor(interface, HID_DEVICET_HID, &hid_desc); if (error) { error = usb_get_extra_descriptor(&interface->endpoint[0], <<< This is #define HID_DEVICET_REPORT, &hid_desc); #define usb_get_extra_descriptor(ifpoint, type, ptr) \ __usb_get_extra_descriptor((ifpoint)->extra, (ifpoint)->extralen, \ <<< rdi rsi type, (void **)ptr) <<< rdx rcx 1e: 49 8b 46 18 mov 0x18(%r14),%rax 22: 48 8d 4d c8 lea -0x38(%rbp),%rcx 26: ba 22 00 00 00 mov $0x22,%edx <<< HID_DEVICET_REPORT >>2b:* 8b 70 38 mov 0x38(%rax),%esi <<< endpoint->extralen *BOOM* 2e: 48 8b 78 30 mov 0x30(%rax),%rdi <<< endpoint->extra 32: e8 ae 2c 07 e1 callq 0xffffffffe1072ce5 The upstream driver was rebased and does not have this bug, so this bug is rhel7-only. The fix is to check the number of endpoints (as it was done in [aiptek] driver fix at http://www.spinics.net/lists/linux-input/msg42294.html, [aiptek] was based on [wacom]). Rhel7 patch follows.
Created attachment 1099055 [details] wacom-null-deref.rhel7.patch
Public via: http://seclists.org/bugtraq/2016/Mar/60
CVEID was requested at: http://seclists.org/oss-sec/2016/q1/606
CVE-2016-3139 was assigned to this flaw, please, use it in the related communications, see http://seclists.org/oss-sec/2016/q1/623.
Thank you for reporting this flaw. The Product Security has rated this flaw as having low security impact (bz1316993), so the patch currently is not planned to be added to the RHEL source trees. The upstream and Fedora is rebased, so the fix may get to the RHEL trees at the next USB subsystem code rebase.