CVE-2021-46953: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-46953 is a vulnerability in the Linux kernel's ACPI GTDT (Generic Timer Description Table) driver. The issue was discovered when the driver fails to properly handle interrupt mappings during watchdog probe failure. The vulnerability affects Linux kernel versions from 4.12.0 up to versions before 4.14.233, 4.19.191, 5.4.118, 5.10.36, 5.11.20, and 5.12.3 (NVD).

The vulnerability occurs in the GTDT driver when it attempts to unmap an interrupt that was mapped earlier during a driver probe failure due to invalid firmware properties. The driver fails to verify whether the interrupt mapping actually succeeded before attempting to unmap it. More critically, if the firmware reports an illegal interrupt number that overlaps with the GIC SGI range, this can result in an IPI (Inter-Processor Interrupt) being unmapped, leading to system instability. The vulnerability has been assigned a CVSS v3.1 base score of 6.7 (Medium) with vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H (NVD).

The vulnerability can lead to corruption of interrupt mappings when the watchdog probe fails. If exploited, particularly in cases where the firmware reports an illegal interrupt number overlapping with the GIC SGI range, it can result in an IPI being unmapped, potentially causing system instability or crashes (Kernel Patch).

The vulnerability requires local access with high privileges to exploit. The attack complexity is low, and no user interaction is required. The vulnerability has been confirmed to be exploitable when specific firmware conditions are met, particularly when illegal interrupt numbers are reported (NVD).

The vulnerability has been patched in the Linux kernel. The fix involves reworking the driver to implement saner behavior by checking whether the interrupt has been mapped before attempting to unmap it. The patch ensures proper handling of interrupt mapping status and prevents potential corruption of interrupt mappings (Kernel Patch).