Executive brief
The Linux kernel's Intel Speed Select Technology (ISST) driver for managing processor performance and power settings contains a bug in how it restores CPU frequency scaling controls after system resume. The flaw causes SST-PP control settings to be written to the wrong memory address for all but the first processor power domain, potentially leaving systems in incorrect power states or performance configurations after wake-up. On multi-socket or multi-domain systems, this degradation could affect processor efficiency and thermal behavior.
Technical details
This is a logic error in the platform/x86 ISST driver's resume path (file: drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c). During suspend, SST-PP control values are correctly read and stored for all power domains. However, on resume, the code uses an incorrect base address variable (`power_domain_info->sst_base`) when restoring those values, which only points to power domain 0. The fix replaces this with the correct per-domain base address (`pd_info->sst_base`), ensuring each power domain's SST-PP control is restored to its own address. The vulnerability affects multi-domain systems and requires no special privileges or network access to trigger—it occurs automatically on every resume cycle. The patch is a single-line fix already merged into stable Linux kernel branches.
Affected products
- Linux Linux kernel multiple versions (see stable branches linux-6.x through linux-7.x)
Timeline
- 2026-08-15: disclosed
- 2026-06-10: patched: upstream fix merged