CVE-2022-22942

El controlador vmwgfx contiene una vulnerabilidad de escalada de privilegios local que permite a los usuarios sin permisos obtener acceso a archivos abiertos por otros procesos en el sistema a través de un puntero de "archivo" colgante.

A use-after-free flaw was found in the Linux kernel’s vmw_execbuf_copy_fence_user function in drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c in vmwgfx. This flaw allows a local attacker with user privileges to cause a privilege escalation problem.

If the vmwgfx driver fails to copy the fence_rep object to userland, it tries to recover by deallocating the (already populated) file descriptor. This is wrong, as the fd gets released via put_unused_fd() which shouldn't be used, as the fd table slot was already populated via the previous call to fd_install(). This leaves userland with a valid fd table entry pointing to a freed file object. The authors use this bug to overwrite a SUID binary with their payload and gain root. Linux kernel versions 4.14-rc1 - 5.17-rc1 are vulnerable. Successfully tested against Ubuntu 22.04.01 with kernel 5.13.12-051312-generic.