Executive Summary

This vulnerability is a bug in the Linux kernel related to the use of an uninitialized stack variable in the function rseq_exit_user_update().

Specifically, a local variable struct rseq_ids named ids is initialized with multiple fields, but due to the indeterminate evaluation order of expressions in the initializer list, the field ids.node_id is computed using ids.cpu_id before ids.cpu_id is actually initialized.

This causes the use of an uninitialized value, leading to a kernel information leak as detected by KMSAN (Kernel Memory Sanitizer).

The issue was fixed by moving the assignment of ids.node_id outside the structure initialization to ensure proper initialization order.

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Impact Analysis

This vulnerability can lead to a kernel information leak, which means that sensitive kernel memory information could be exposed unintentionally.

Such leaks can potentially be exploited by attackers to gain insights into kernel memory layout or other sensitive data, which might aid in further attacks or privilege escalation.

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