CVE-2018-18397

La implementación de userfaultfd en el kernel de Linux en versiones anteriores a la 4.17 gestiona de manera incorrecta para ciertas llamadas ioctl UFFDIO_, tal y como queda demostrado al permitir que usuarios locales escriban datos en huecos en un archivo tmpfs (si el usuario tiene acceso de solo lectura a dicho archivo que contiene huecos). Esto está relacionado con fs/userfaultfd.c y mm/userfaultfd.c.

A flaw was found in the Linux kernel with files on tmpfs and hugetlbfs. An attacker is able to bypass file permissions on filesystems mounted with tmpfs/hugetlbs to modify a file and possibly disrupt normal system behavior. At this time there is an understanding there is no crash or privilege escalation but the impact of modifications on these filesystems of files in production systems may have adverse affects.

USN-3903-1 fixed vulnerabilities in the Linux kernel for Ubuntu 18.10. This update provides the corresponding updates for the Linux Hardware Enablement kernel from Ubuntu 18.10 for Ubuntu 18.04 LTS. Jason Wang discovered that the vhost net driver in the Linux kernel contained an out of bounds write vulnerability. An attacker in a guest virtual machine could use this to cause a denial of service or possibly execute arbitrary code in the host kernel. Various other issues were also addressed.