CVE-2024-9676: Podman: buildah: cri-o: symlink traversal vulnerability in the containers/storage library can cause denial of service (dos)

A symlink traversal vulnerability in the containers/storage library can cause Podman, Buildah, and CRI-O to hang and potentially be DoSed via OOM kill when running a malicious image using an automatically assigned user namespace (--userns=auto in Podman and Buildah). The containers/storage library will read /etc/passwd inside the container, but does not properly validate if that file is a symlink, which can be used to cause the library to read an arbitrary file on the host. This file is only read, and if it does not properly parse as a copy of /etc/passwd it will cause an error (there is a small risk of information disclosure via the error message here as elements of the file that failed to parse can be included, but this is only as the user running Podman/Buildah/CRI-O so it wouldn't be a file they did not already have access to). The report here discovered that you can symlink /etc/passwd in the container to a FIFO on the host, causing a hang as the file cannot be completely read (or an OOM condition if the FIFO is continuously written to, which was then ready by Podman). This hang could occur in a critical section in the c/storage library, blocking other processes from creating containers, but could be easily solved via a SIGKILL of the affected process. The ability to potentially crash the CRI-O service via OOM kill could be more relevant, though the attacker would have to know the path of a FIFO that is regularly being written to on the host in order to do this.