CVE-2024-56761

Summary

CVE-2024-56761 is a vulnerability affecting the Linux kernel that can lead to a dead loop if the Wake-up From Exception (WFE) state is not cleared properly in the x86 FRED (Fast Response Exception Delivery) subsystem. The WFE state is saved and restored in FRED's expanded CS area, allowing it to persist across instruction boundaries. If the WFE state is not cleared, the CPU may enter a dead loop when encountering a missing-ENDBRANCH condition. This issue is not related to the Interrupt Descriptor Table (IDT) or the IRET instruction, as they do not preserve WFE or set it during execution. To mitigate this vulnerability, software must ensure that the WFE state is cleared in the appropriate circumstances to avoid dead locking. Failure to clear WFE in other situations could result in security-relevant bugs.

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