CVE-2017-7889

The mm subsystem in the Linux kernel through 3.2 does not properly enforce the CONFIG_STRICT_DEVMEM protection mechanism, which allows local users to read or write to kernel memory locations in the first megabyte (and bypass slab-allocation access restrictions) via an application that opens the /dev/mem file, related to arch/x86/mm/init.c and drivers/char/mem.c.

Weakness

The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.

Affected Software

Potential Mitigations

• Run the code in a “jail” or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
• OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
• This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
• Be careful to avoid CWE-243 and other weaknesses related to jails.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/1.html
• https://cwe.mitre.org/data/definitions/122.html
• https://cwe.mitre.org/data/definitions/127.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/180.html
• https://cwe.mitre.org/data/definitions/206.html
• https://cwe.mitre.org/data/definitions/234.html
• https://cwe.mitre.org/data/definitions/60.html
• https://cwe.mitre.org/data/definitions/61.html
• https://cwe.mitre.org/data/definitions/62.html
• https://cwe.mitre.org/data/definitions/642.html

References

• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a4866aa812518ed1a37d8ea0c881dc946409de94
• http://www.debian.org/security/2017/dsa-3945
• http://www.openwall.com/lists/oss-security/2017/04/16/4
• http://www.securityfocus.com/bid/97690
• https://access.redhat.com/errata/RHSA-2017:1842
• https://access.redhat.com/errata/RHSA-2017:2077
• https://access.redhat.com/errata/RHSA-2017:2669
• https://access.redhat.com/errata/RHSA-2018:1854
• https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=b8f254aa17f720053054c4ecff3920973a83b9d6
• https://github.com/torvalds/linux/commit/a4866aa812518ed1a37d8ea0c881dc946409de94
• https://usn.ubuntu.com/3583-1/
• https://usn.ubuntu.com/3583-2/