Executive Summary

This vulnerability in the Linux kernel relates to the s390 architecture's kernel entry code. Previously, the r12 register was loaded with the current task pointer for use by certain macros (BPENTER/BPEXIT). A recent commit removed the use of these macros and the loading of r12 but failed to clear the r12 register on kernel entry. This omission could leave sensitive data in the r12 register. The fix involved adding an instruction to clear (scrub) the r12 register on all kernel entry points to ensure consistency and prevent potential information leakage.

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Impact Analysis

If the r12 register is not cleared on kernel entry, it may retain sensitive information from previous tasks. This could potentially lead to information leakage between processes or tasks, undermining system security and isolation. Attackers or malicious code might exploit this to gain unauthorized access to sensitive data.

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Mitigation Strategies

The vulnerability has been resolved by a patch in the Linux kernel that scrubs the r12 register on kernel entry for the s390 architecture. To mitigate this vulnerability, you should update your Linux kernel to a version that includes the fix (commit f33f2d4c7c80 or later).

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