Executive Summary

This vulnerability exists in the Linux kernel's arm64/gcs component, specifically in the function arch_set_shadow_stack_status().

The issue arises because alloc_gcs() returns an error-encoded pointer on failure, which originates from do_mmap(), rather than returning NULL.

However, the current code only checks for NULL to detect errors, which fails to identify these error pointers.

As a result, the system might use an invalid GCS (Generic Code Stack) address.

The fix involves using IS_ERR_VALUE() to properly detect error pointers, aligning with the error checking done in gcs_alloc_thread_stack().

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Impact Analysis

If this vulnerability is exploited or triggered, it could lead to the use of invalid memory addresses related to the Generic Code Stack.

This could potentially cause system instability, crashes, or unpredictable behavior in the Linux kernel on affected arm64 systems.

Such instability might be leveraged by attackers to cause denial of service or other unintended effects.

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