Processor vulnerability
CVE-2022-40982
A speculative AVX gather that faults can return stale vector register data of other programs, the kernel, other guests or SGX enclaves.
- Name
- Gather Data Sampling
- Also known as
- GDS, Downfall
- Kind
- Data sampling
- CVE published
- 2023-08-11 CVE record
- Advisories
- INTEL-SA-00828
- Linux reports it in
gather_data_sampling
The gather instructions of AVX2 and AVX-512 load several elements
from scattered addresses into a vector register. On affected Intel
processors, a gather that hits a fault while running speculatively
can pass on stale data held in internal vector registers instead of
the loaded elements. The victim needs only to use vector registers,
not gathers; the attacker samples with gathers. The leak crosses
user and kernel, guests and SGX.What the sources say of each microarchitecture. Intel’s list gives each CPUID family, model and stepping it covers, with Intel’s mitigation for it (Software, MCU for a microcode update, or Hardware).
Affected processors
11 of the 28 microarchitectures listed are affected in all or some of their models.
| Microarchitecture | Status | Detail | Source |
|---|---|---|---|
| Skylake | Affected | 06_5EH stepping 3 (1. Skylake Xeon E3 - 2. Skylake H - 3. Skylake S): MCU | Intel’s list |
| Kaby Lake | Affected | 06_8EH stepping 9 (1. Amber Lake-Y - 2. Kaby Lake U - 3. Kaby Lake U23e - 4. Kaby Lake Y): MCU 06_8EH stepping C (1. Whiskey Lake V - 2. Comet Lake U42 - 3. Amber Lake Y): MCU 06_9EH stepping 9 (1. Kaby Lake S - 2. Kaby Lake Xeon E3): MCU | Intel’s list |
| Coffee Lake | Affected | 06_8EH stepping A (1. Coffee Lake U43e - 2. Whiskey Lake): MCU 06_8EH stepping B (Whiskey Lake U): MCU 06_8EH stepping C (1. Whiskey Lake V - 2. Comet Lake U42 - 3. Amber Lake Y): MCU 06_9EH stepping A (Coffee Lake H): MCU 06_9EH stepping C (Coffee Lake S): MCU 06_9EH stepping D (1. Coffee Lake H - 2. Coffee Lake Xeon E - 3. Coffee Lake S): MCU | Intel’s list |
| Comet Lake | Affected | 06_8EH stepping C (1. Whiskey Lake V - 2. Comet Lake U42 - 3. Amber Lake Y): MCU 06_A5H stepping 2 (Comet Lake H): MCU 06_A5H stepping 3 (Comet Lake-S): MCU 06_A5H stepping 5 (Comet Lake-S): MCU 06_A6H stepping 0 (Comet Lake U62): MCU 06_A6H stepping 1 (Comet Lake U62): MCU | Intel’s list |
| Ice Lake (client) | Affected | 06_7EH stepping 5 (Ice Lake U - Ice Lake Y): MCU | Intel’s list |
| Tiger Lake | Affected | 06_8CH stepping 1 (Tiger Lake U): MCU 06_8CH stepping 1 (Tiger Lake U): MCU 06_8CH stepping 2 (1. Tiger Lake U Refresh - 2. Tiger Lake H35): MCU 06_8DH stepping 1 (Tiger Lake H): MCU 06_8DH stepping 1 (Tiger Lake H): MCU | Intel’s list |
| Rocket Lake | Affected | 06_A7H stepping 1 (Rocket Lake): MCU | Intel’s list |
| Cascade Lake | Affected | Linux 7.3 lists INTEL_SKYLAKE_X steppings 5 to 7 in cpu_vuln_blacklist with GDS | Linux 7.3 |
| Cooper Lake | Affected | 06_55H stepping B (Cooper Lake): MCU | Intel’s list |
| Ice Lake (server) | Affected | 06_6AH stepping 6 (Ice Lake Xeon-SP): MCU 06_6CH stepping All (Ice Lake Xeon D (Idaville)): MCU | Intel’s list |
| Skylake-SP | Some models | 06_55H stepping 3 (Skylake Server): Not Affected 06_55H stepping 4 (1. Skylake Server - 2. Skylake D/Bakerville): MCU | Intel’s list |
| Haswell | Not affected | 06_3FH stepping 2 (Haswell Server EP/EP4S): Not Affected 06_3FH stepping 4 (Haswell Server EX): Not Affected | Intel’s list |
| Broadwell | Not affected | 06_4FH stepping 1 (1. Broadwell Server E/EP/EP4S - 2. Broadwell Server EX): Not Affected 06_56H stepping 3 (Broadwell DE V2 - V3): Not Affected 06_56H stepping 4 (Broadwell DE Y0): Not Affected 06_56H stepping 5 (Hewitt Lake (Broadwell DE)): Not Affected | Intel’s list |
| Alder Lake | Not affected | 06_97H stepping 2 (Alder Lake S (Golden Cove - Gracemont)): Not Affected 06_97H stepping 5 (Alder Lake S (Golden Cove - Gracemont)): Not Affected 06_97H stepping 5 (Catlow (Golden Cove)): Not Affected 06_9AH stepping 3 (1. Alder Lake H (Golden Cove - Gracemont) - 2. Alder Lake P (Golden Cove - Gracemont)): Not Affected 06_9AH stepping 4 (Alder Lake U (Golden Cove - Gracemont)): Not Affected | Intel’s list |
| Raptor Lake | Not affected | 06_B7H stepping 1 (1. Raptor Lake S - 2. Raptor Lake HX (Raptor Cove/Gracemont)): Not Affected 06_B7H stepping 1 (Catlow (Raptor Cove)): Not Affected 06_BAH stepping 2 - 3 - 8 (1. Raptor Lake P - 2. Raptor Lake H + refresh - 3. Raptor Lake U + refresh (Raptor Cove/Gracemont)): Not Affected 06_BFH stepping 2 - 5 (Raptor Lake S (Raptor Cove/Gracemont)): Not Affected | Intel’s list |
| Meteor Lake | Not affected | 06_AAH stepping 4 (Meteor Lake U/H/PS (Redwood Cove - Crestmont)): Not Affected | Intel’s list |
| Arrow Lake | Not affected | 06_B5H stepping 0 (Arrow Lake U (Redwood Cove - Crestmont)): Not Affected 06_C5H stepping 2 (Arrow Lake H (Lion Cove - Skymont)): Not Affected 06_C6H stepping 2 (Arrow Lake H/HX/S/S Plus (Lion Cove - Skymont)): Not Affected | Intel’s list |
| Lunar Lake | Not affected | 06_BDH stepping 1 (Lunar Lake (Lion Cove - Skymont)): Not Affected | Intel’s list |
| Panther Lake | Not affected | 06_CCH stepping 2 - 3 (Panther Lake (Cougar Cove - Darkmont)): Not Affected | Intel’s list |
| Emerald Rapids | Not affected | 06_CFH stepping 2 (Emerald Rapids (Raptor Cove)): Not Affected | Intel’s list |
| Sapphire Rapids | Not affected | 06_8FH stepping 5 - 6 - 7 - 8 (1. Sapphire Rapids - 2. Sapphire Rapids Edge Enhanced (Golden Cove)): Not Affected 06_8FH stepping 5 - 6 - 8 (Sapphire Rapids (Golden Cove) - Sapphire Rapids HBM): Not Affected | Intel’s list |
| Granite Rapids | Not affected | 06_ADH stepping 1 (Granite Rapids (Redwood Cove)): Not Affected 06_ADH stepping 1 (Granite Rapids (Redwood Cove)): Not Affected 06_ADH stepping 1 (Granite Rapids R1S (Redwood Cove)): Not Affected 06_AEH stepping 1 (Granite Rapids D (Redwood Cove)/Kaseyville): Not Affected | Intel’s list |
| Sierra Forest | Not affected | 06_AFH stepping 3 (Sierra Forest (Crestmont)): Not Affected | Intel’s list |
| Clearwater Forest | Not affected | 06_DDH stepping 1 (Clearwater Forest (Darkmont)): Not Affected | Intel’s list |
| Goldmont | Not affected | 06_5CH stepping A (Apollo Lake): Not Affected 06_5FH stepping All (Denverton (Goldmont)): Not Affected | Intel’s list |
| Goldmont Plus | Not affected | 06_7AH stepping 8 (Gemini Lake): Not Affected | Intel’s list |
| Tremont | Not affected | 06_86H stepping 5 (Snow Ridge BTS (Tremont)): Not Affected 06_86H stepping 7 (Parker Ridge / Snow Ridge NS/NX/BTS): Not Affected 06_96H stepping All (Elkhart Lake (Tremont)): Not Affected 06_9CH stepping All (Jasper Lake (Tremont)): Not Affected | Intel’s list |
| Gracemont | Not affected | 06_9AH stepping 4 (Arizona Beach (Gracemont)): Not Affected 06_BEH stepping 0 (Alder Lake N (Gracemont)/Twin Lake): Not Affected | Intel’s list |
Mitigations
- Microcode: Intel's microcode closes the leak in gathers, at a cost to their speed; IA32_MCU_OPT_CTRL (MSR 123H) can turn it off, and lock it on. The processor reports itself not affected with GDS_NO, bit 26 of IA32_ARCH_CAPABILITIES. Instructions: VPGATHERDD, WRMSR. Source.
- Kernel: Without the microcode, Linux can turn AVX off (gather_data_sampling=force), by clearing the YMM state from XCR0. Source.
How to check a machine
On Linux, /sys/devices/system/cpu/vulnerabilities/gather_data_sampling holds one of these lines:
Not affectedVulnerableVulnerable: No microcodeMitigation: AVX disabled, no microcodeMitigation: MicrocodeMitigation: Microcode (locked)Unknown: Dependent on hypervisor status