forked from torvalds/linux
-
Notifications
You must be signed in to change notification settings - Fork 133
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Merge pull request #4549 from plbossart/merge/sound-upstream-20230825
Merge/sound upstream 20230825
- Loading branch information
Showing
626 changed files
with
16,813 additions
and
4,622 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
|
@@ -513,17 +513,18 @@ Description: information about CPUs heterogeneity. | |
| cpu_capacity: capacity of cpuX. | ||
|
|
||
| What: /sys/devices/system/cpu/vulnerabilities | ||
| /sys/devices/system/cpu/vulnerabilities/gather_data_sampling | ||
| /sys/devices/system/cpu/vulnerabilities/itlb_multihit | ||
| /sys/devices/system/cpu/vulnerabilities/l1tf | ||
| /sys/devices/system/cpu/vulnerabilities/mds | ||
| /sys/devices/system/cpu/vulnerabilities/meltdown | ||
| /sys/devices/system/cpu/vulnerabilities/mmio_stale_data | ||
| /sys/devices/system/cpu/vulnerabilities/retbleed | ||
| /sys/devices/system/cpu/vulnerabilities/spec_store_bypass | ||
| /sys/devices/system/cpu/vulnerabilities/spectre_v1 | ||
| /sys/devices/system/cpu/vulnerabilities/spectre_v2 | ||
| /sys/devices/system/cpu/vulnerabilities/spec_store_bypass | ||
| /sys/devices/system/cpu/vulnerabilities/l1tf | ||
| /sys/devices/system/cpu/vulnerabilities/mds | ||
| /sys/devices/system/cpu/vulnerabilities/srbds | ||
| /sys/devices/system/cpu/vulnerabilities/tsx_async_abort | ||
| /sys/devices/system/cpu/vulnerabilities/itlb_multihit | ||
| /sys/devices/system/cpu/vulnerabilities/mmio_stale_data | ||
| /sys/devices/system/cpu/vulnerabilities/retbleed | ||
| Date: January 2018 | ||
| Contact: Linux kernel mailing list <[email protected]> | ||
| Description: Information about CPU vulnerabilities | ||
|
|
||
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
109 changes: 109 additions & 0 deletions
109
Documentation/admin-guide/hw-vuln/gather_data_sampling.rst
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| .. SPDX-License-Identifier: GPL-2.0 | ||
| GDS - Gather Data Sampling | ||
| ========================== | ||
|
|
||
| Gather Data Sampling is a hardware vulnerability which allows unprivileged | ||
| speculative access to data which was previously stored in vector registers. | ||
|
|
||
| Problem | ||
| ------- | ||
| When a gather instruction performs loads from memory, different data elements | ||
| are merged into the destination vector register. However, when a gather | ||
| instruction that is transiently executed encounters a fault, stale data from | ||
| architectural or internal vector registers may get transiently forwarded to the | ||
| destination vector register instead. This will allow a malicious attacker to | ||
| infer stale data using typical side channel techniques like cache timing | ||
| attacks. GDS is a purely sampling-based attack. | ||
|
|
||
| The attacker uses gather instructions to infer the stale vector register data. | ||
| The victim does not need to do anything special other than use the vector | ||
| registers. The victim does not need to use gather instructions to be | ||
| vulnerable. | ||
|
|
||
| Because the buffers are shared between Hyper-Threads cross Hyper-Thread attacks | ||
| are possible. | ||
|
|
||
| Attack scenarios | ||
| ---------------- | ||
| Without mitigation, GDS can infer stale data across virtually all | ||
| permission boundaries: | ||
|
|
||
| Non-enclaves can infer SGX enclave data | ||
| Userspace can infer kernel data | ||
| Guests can infer data from hosts | ||
| Guest can infer guest from other guests | ||
| Users can infer data from other users | ||
|
|
||
| Because of this, it is important to ensure that the mitigation stays enabled in | ||
| lower-privilege contexts like guests and when running outside SGX enclaves. | ||
|
|
||
| The hardware enforces the mitigation for SGX. Likewise, VMMs should ensure | ||
| that guests are not allowed to disable the GDS mitigation. If a host erred and | ||
| allowed this, a guest could theoretically disable GDS mitigation, mount an | ||
| attack, and re-enable it. | ||
|
|
||
| Mitigation mechanism | ||
| -------------------- | ||
| This issue is mitigated in microcode. The microcode defines the following new | ||
| bits: | ||
|
|
||
| ================================ === ============================ | ||
| IA32_ARCH_CAPABILITIES[GDS_CTRL] R/O Enumerates GDS vulnerability | ||
| and mitigation support. | ||
| IA32_ARCH_CAPABILITIES[GDS_NO] R/O Processor is not vulnerable. | ||
| IA32_MCU_OPT_CTRL[GDS_MITG_DIS] R/W Disables the mitigation | ||
| 0 by default. | ||
| IA32_MCU_OPT_CTRL[GDS_MITG_LOCK] R/W Locks GDS_MITG_DIS=0. Writes | ||
| to GDS_MITG_DIS are ignored | ||
| Can't be cleared once set. | ||
| ================================ === ============================ | ||
|
|
||
| GDS can also be mitigated on systems that don't have updated microcode by | ||
| disabling AVX. This can be done by setting gather_data_sampling="force" or | ||
| "clearcpuid=avx" on the kernel command-line. | ||
|
|
||
| If used, these options will disable AVX use by turning off XSAVE YMM support. | ||
| However, the processor will still enumerate AVX support. Userspace that | ||
| does not follow proper AVX enumeration to check both AVX *and* XSAVE YMM | ||
| support will break. | ||
|
|
||
| Mitigation control on the kernel command line | ||
| --------------------------------------------- | ||
| The mitigation can be disabled by setting "gather_data_sampling=off" or | ||
| "mitigations=off" on the kernel command line. Not specifying either will default | ||
| to the mitigation being enabled. Specifying "gather_data_sampling=force" will | ||
| use the microcode mitigation when available or disable AVX on affected systems | ||
| where the microcode hasn't been updated to include the mitigation. | ||
|
|
||
| GDS System Information | ||
| ------------------------ | ||
| The kernel provides vulnerability status information through sysfs. For | ||
| GDS this can be accessed by the following sysfs file: | ||
|
|
||
| /sys/devices/system/cpu/vulnerabilities/gather_data_sampling | ||
|
|
||
| The possible values contained in this file are: | ||
|
|
||
| ============================== ============================================= | ||
| Not affected Processor not vulnerable. | ||
| Vulnerable Processor vulnerable and mitigation disabled. | ||
| Vulnerable: No microcode Processor vulnerable and microcode is missing | ||
| mitigation. | ||
| Mitigation: AVX disabled, | ||
| no microcode Processor is vulnerable and microcode is missing | ||
| mitigation. AVX disabled as mitigation. | ||
| Mitigation: Microcode Processor is vulnerable and mitigation is in | ||
| effect. | ||
| Mitigation: Microcode (locked) Processor is vulnerable and mitigation is in | ||
| effect and cannot be disabled. | ||
| Unknown: Dependent on | ||
| hypervisor status Running on a virtual guest processor that is | ||
| affected but with no way to know if host | ||
| processor is mitigated or vulnerable. | ||
| ============================== ============================================= | ||
|
|
||
| GDS Default mitigation | ||
| ---------------------- | ||
| The updated microcode will enable the mitigation by default. The kernel's | ||
| default action is to leave the mitigation enabled. |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Oops, something went wrong.