vulnerability alert CVE-2012-4576

FreeBSD: privilege escalation via Linux SIOCGIFCONF

Synthesis of the vulnerability

An attacker can create a binary program for Linux using the SIOCGIFCONF ioctl, and by running it on FreeBSD, can elevate his privileges.
Impacted products: FreeBSD.
Severity: 2/4.
Creation date: 23/11/2012.
Identifiers: BID-56654, CVE-2012-4576, FreeBSD-SA-12:08.linux, VIGILANCE-VUL-12181.

Description of the vulnerability

FreeBSD contains a kernel module to execute Linux binary programs.

The SIOCGIFCONF ioctl is used to retrieve the IP addresses of a network interface. In order to do so, the user program provides an argument of type "struct ifconf", containing a pointer (ifc_buf) to the buffer that the kernel should fill.

The function linux_ifconf() in sys/compat/linux/linux_ioctl.c implements this ioctl. However, the kernel does not check whether the destination buffer is in the data user space, so an attacker can make the kernel write to a memory address with its own privileges.

An attacker can create a binary program for Linux using the SIOCGIFCONF ioctl, and by running it on FreeBSD, can elevate his privileges.
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