SELinux Policy File Multiple Opens in Linux Kernel

Executive Summary

This vulnerability exists in the Linux kernel's SELinux implementation, specifically related to the handling of the /sys/fs/selinux/policy file. Previously, only one process could open this policy file at a time, which allowed that process to block others from reading the kernel policy. This was originally intended to prevent inconsistent views of the policy size and uncontrolled kernel memory allocation by userspace, but it also created a denial of service condition for other processes.

The fix removes the restriction that only a single open is allowed by eliminating the policy_opened flag and reducing the scope of the policy mutex lock, allowing multiple processes to open the policy file simultaneously without blocking each other.

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Impact Analysis

This vulnerability can allow a process to block other processes from reading the SELinux kernel policy by holding the single allowed open on the /sys/fs/selinux/policy file. This could lead to denial of service conditions where legitimate processes are unable to access the policy information they need, potentially disrupting security enforcement or system management tasks.

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