runc can be confused to create empty files/directories on the host

runc is a CLI tool for spawning and running containers according to the OCI specification. runc 1.1.13 and earlier, as well as 1.2.0-rc2 and earlier, can be tricked into creating empty files or directories in arbitrary locations in the host filesystem by sharing a volume between two containers and exploiting a race with `os.MkdirAll`. While this could be used to create empty files, existing files would not be truncated. An attacker must have the ability to start containers using some kind of custom volume configuration. Containers using user namespaces are still affected, but the scope of places an attacker can create inodes can be significantly reduced. Sufficiently strict LSM policies (SELinux/Apparmor) can also in principle block this attack -- we suspect the industry standard SELinux policy may restrict this attack's scope but the exact scope of protection hasn't been analysed. This is exploitable using runc directly as well as through Docker and Kubernetes. The issue is fixed in runc v1.1.14 and v1.2.0-rc3. Some workarounds are available. Using user namespaces restricts this attack fairly significantly such that the attacker can only create inodes in directories that the remapped root user/group has write access to. Unless the root user is remapped to an actual user on the host (such as with rootless containers that don't use `/etc/sub[ug]id`), this in practice means that an attacker would only be able to create inodes in world-writable directories. A strict enough SELinux or AppArmor policy could in principle also restrict the scope if a specific label is applied to the runc runtime, though neither the extent to which the standard existing policies block this attack nor what exact policies are needed to sufficiently restrict this attack have been thoroughly tested.

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

允许符号链接跟随的竞争条件

runc 安全漏洞

runc是Open Container Initiative开源的一款用于根据OCI规范生成和运行容器的CLI（命令行界面）工具。 runc 1.1.13版本及之前版本和1.2.0-rc2版本及之前版本存在安全漏洞，该漏洞源于在使用特定的卷配置共享体积的两个容器之间，利用os.MkdirAll的竞争条件，可能会被诱骗在主机文件系统的任意位置创建空文件或目录。

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