Описание
The Linux kernel allows userspace processes to enable mitigations by calling prctl with PR_SET_SPECULATION_CTRL which disables the speculation feature as well as by using seccomp. We had noticed that on VMs of at least one major cloud provider, the kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. The same behavior can be observed on a bare-metal machine when forcing the mitigation to IBRS on boot command line.
This happened because when plain IBRS was enabled (not enhanced IBRS), the kernel had some logic that determined that STIBP was not needed. The IBRS bit implicitly protects against cross-thread branch target injection. However, with legacy IBRS, the IBRS bit was cleared on returning to userspace, due to performance reasons, which disabled the implicit STIBP and left userspace threads vulnerable to cross-thread branch target injection against which STIBP protects.
It was found that the Linux Kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. The kernel failed to protect applications that attempted to protect against Spectre v2 leaving them open to attack from other processes running on the same physical core in another hyperthread.
Меры по смягчению последствий
This flaw can be mitigated by disabling Simultaneous Multithreading (SMT). For instructions on how to disable SMT in RHEL, please see https://access.redhat.com/solutions/rhel-smt.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Out of support scope | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Fixed | RHSA-2023:6901 | 14.11.2023 |
| Red Hat Enterprise Linux 8 | kernel | Fixed | RHSA-2023:7077 | 14.11.2023 |
| Red Hat Enterprise Linux 8.6 Extended Update Support | kernel | Fixed | RHSA-2024:0412 | 25.01.2024 |
| Red Hat Enterprise Linux 8.8 Extended Update Support | kernel | Fixed | RHSA-2024:3810 | 11.06.2024 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2023:4377 | 01.08.2023 |
| Red Hat Enterprise Linux 9 | kernel-rt | Fixed | RHSA-2023:4378 | 01.08.2023 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2023:4377 | 01.08.2023 |
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Дополнительная информация
Статус:
EPSS
5.6 Medium
CVSS3
Связанные уязвимости
The Linux kernel allows userspace processes to enable mitigations by calling prctl with PR_SET_SPECULATION_CTRL which disables the speculation feature as well as by using seccomp. We had noticed that on VMs of at least one major cloud provider, the kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. The same behavior can be observed on a bare-metal machine when forcing the mitigation to IBRS on boot command line. This happened because when plain IBRS was enabled (not enhanced IBRS), the kernel had some logic that determined that STIBP was not needed. The IBRS bit implicitly protects against cross-thread branch target injection. However, with legacy IBRS, the IBRS bit was cleared on returning to userspace, due to performance reasons, which disabled the implicit STIBP and left userspace threads vulnerable to cross-thread branch target injection against which STIBP protects.
The Linux kernel allows userspace processes to enable mitigations by calling prctl with PR_SET_SPECULATION_CTRL which disables the speculation feature as well as by using seccomp. We had noticed that on VMs of at least one major cloud provider, the kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. The same behavior can be observed on a bare-metal machine when forcing the mitigation to IBRS on boot command line. This happened because when plain IBRS was enabled (not enhanced IBRS), the kernel had some logic that determined that STIBP was not needed. The IBRS bit implicitly protects against cross-thread branch target injection. However, with legacy IBRS, the IBRS bit was cleared on returning to userspace, due to performance reasons, which disabled the implicit STIBP and left userspace threads vulnerable to cross-thread branch target injection against which STIBP protects.
The Linux kernel allows userspace processes to enable mitigations by c ...
Уязвимость функции prctl ядра операционной системы Linux, позволяющая нарушителю получить доступ к защищаемой информации
EPSS
5.6 Medium
CVSS3