Buffer Overflow in Linux Kernel kheaders Causes Kernel Panic

Executive Summary

This vulnerability in the Linux kernel's kheaders component involves the use of a 'char' declaration for kernel_headers_data, which causes a buffer overflow detection under CONFIG_FORTIFY_SOURCE when memcpy() checks the size of destination and source buffers. The issue arises because these addresses are treated as byte arrays, and defining them as 'char' trips the size check. The fix was to define kernel_headers_data as an array instead of a 'char', preventing the buffer overflow detected during operations like reading /sys/kernel/kheaders.tar.xz.

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Impact Analysis

This vulnerability can cause a kernel buffer overflow leading to a kernel BUG and potential system crash or instability when accessing kernel headers, such as reading /sys/kernel/kheaders.tar.xz. This could result in denial of service or system reliability issues.

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Detection Guidance

This vulnerability can be detected by attempting to read the kernel headers archive and observing if a buffer overflow or kernel BUG occurs. For example, running the command: cat /sys/kernel/kheaders.tar.xz >> /dev/null may trigger the issue, resulting in messages such as 'detected buffer overflow in memcpy' and a kernel BUG at lib/string_helpers.c. Monitoring kernel logs for such errors can help detect the vulnerability.

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Mitigation Strategies

Immediate mitigation involves updating the Linux kernel to a version where this vulnerability is resolved, which includes changing the kernel_headers_data declaration from char to an array to avoid buffer overflow in memcpy under CONFIG_FORTIFY_SOURCE. Until an update is applied, avoid operations that read /sys/kernel/kheaders.tar.xz to prevent triggering the bug.

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