ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered If a synchronous error is detected as a result of user-space process triggering a 2-bit uncorrected error, the CPU will take a synchronous error exception such as Synchronous External Abort (SEA) on Arm64. The kernel will queue a memory_failure() work which poisons the related page, unmaps the page, and then sends a SIGBUS to the process, so that a system wide panic can be avoided. However, no memory_failure() work will be queued when abnormal synchronous errors occur. These errors can include situations like invalid PA, unexpected severity, no memory failure config support, invalid GUID section, etc. In such a case, the user-space process will trigger SEA again. This loop can potentially exceed the platform firmware threshold or even trigger a kernel hard lockup, leading to a system reboot. Fix it by performing a force kill if no memory_failure() work is queued for synchronous errors. [ rjw: Changelog edits ]

References

• https://git.kernel.org/stable/c/2fbc85da9ac9386bd89fcc94e0aadaea19d47784
• https://git.kernel.org/stable/c/082735fbcdb6cd0cf20fbec94516ab2996f1cdd5
• https://git.kernel.org/stable/c/cfc9bc15bda6fd0c496cbe2c628564d4d7c332c1
• https://git.kernel.org/stable/c/af089e41811a1ad6a7b2b80e839a73ec4c3cecdd
• https://git.kernel.org/stable/c/3cb4f18797247985b0f51d5300f8cb6c78f343ea
• https://git.kernel.org/stable/c/79a5ae3c4c5eb7e38e0ebe4d6bf602d296080060