CVE-2021-46990
powerpc/64s: Fix crashes when toggling entry flush barrier
Severity Score
Exploit Likelihood
Affected Versions
Public Exploits
0Exploited in Wild
-Decision
Descriptions
In the Linux kernel, the following vulnerability has been resolved:
powerpc/64s: Fix crashes when toggling entry flush barrier
The entry flush mitigation can be enabled/disabled at runtime via a
debugfs file (entry_flush), which causes the kernel to patch itself to
enable/disable the relevant mitigations.
However depending on which mitigation we're using, it may not be safe to
do that patching while other CPUs are active. For example the following
crash:
sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20
Shows that we returned to userspace with a corrupted LR that points into
the kernel, due to executing the partially patched call to the fallback
entry flush (ie. we missed the LR restore).
Fix it by doing the patching under stop machine. The CPUs that aren't
doing the patching will be spinning in the core of the stop machine
logic. That is currently sufficient for our purposes, because none of
the patching we do is to that code or anywhere in the vicinity.
En el kernel de Linux, se resolvió la siguiente vulnerabilidad: powerpc/64s: soluciona fallas al alternar la barrera de descarga de entrada. La mitigación de descarga de entrada se puede habilitar/deshabilitar en tiempo de ejecución a través de un archivo debugfs (entry_flush), lo que hace que el kernel se parchee a sí mismo. habilitar/deshabilitar las mitigaciones relevantes. Sin embargo, dependiendo de la mitigación que estemos usando, puede que no sea seguro aplicar ese parche mientras otras CPU están activas. Por ejemplo, el siguiente bloqueo: durmiente[15639]: segfault (11) en c000000000004c20 nip c000000000004c20 lr c000000000004c20 Muestra que regresamos al espacio de usuario con un LR corrupto que apunta al kernel, debido a la ejecución de la llamada parcialmente parcheada a la entrada de respaldo descarga ( es decir, nos perdimos la restauración de LR). Arréglelo haciendo el parche debajo de detener la máquina. Las CPU que no estén aplicando los parches girarán en el núcleo de la lógica de detención de la máquina. Actualmente, eso es suficiente para nuestros propósitos, porque ninguno de los parches que hacemos se aplica a ese código ni a ningún lugar cercano.
CVSS Scores
SSVC
- Decision:Track
Timeline
- 2024-02-27 CVE Reserved
- 2024-02-28 CVE Published
- 2024-02-29 EPSS Updated
- 2024-08-04 CVE Updated
- ---------- Exploited in Wild
- ---------- KEV Due Date
- ---------- First Exploit
CWE
CAPEC
References (16)
| URL | Tag | Source |
|---|---|---|
| https://git.kernel.org/stable/c/4a1e90af718d1489ffcecc8f52486c4f5dc0f7a6 | Vuln. Introduced | |
| https://git.kernel.org/stable/c/fa4bf9f38184ed7ca4916eb64f8c767d1e279c1f | Vuln. Introduced | |
| https://git.kernel.org/stable/c/db01cad9efe3c3838a6b3a3f68affd295c4b92d6 | Vuln. Introduced | |
| https://git.kernel.org/stable/c/f69bb4e51f41973fb7594be1479fa689831efe1a | Vuln. Introduced | |
| https://git.kernel.org/stable/c/b65458b6be8032c5179d4f562038575d7b3a6be3 | Vuln. Introduced | |
| https://git.kernel.org/stable/c/f79643787e0a0762d2409b7b8334e83f22d85695 | Vuln. Introduced | |
| https://git.kernel.org/stable/c/e590b36718d6e740b7b19514f710402a6499164c | Vuln. Introduced |
| URL | Date | SRC |
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| URL | Date | SRC |
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Affected Vendors, Products, and Versions
| Vendor | Product | Version | Other | Status | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Vendor | Product | Version | Other | Status | <-- --> | Vendor | Product | Version | Other | Status |
| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 4.4.245 < 4.4.269 Search vendor "Linux" for product "Linux Kernel" and version " >= 4.4.245 < 4.4.269" | en |
Affected
| ||||||
| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 4.9.245 < 4.9.269 Search vendor "Linux" for product "Linux Kernel" and version " >= 4.9.245 < 4.9.269" | en |
Affected
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| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 4.14.208 < 4.14.233 Search vendor "Linux" for product "Linux Kernel" and version " >= 4.14.208 < 4.14.233" | en |
Affected
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| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 4.19.159 < 4.19.191 Search vendor "Linux" for product "Linux Kernel" and version " >= 4.19.159 < 4.19.191" | en |
Affected
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| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 5.4.79 < 5.4.120 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4.79 < 5.4.120" | en |
Affected
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| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 5.10 < 5.10.38 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.10 < 5.10.38" | en |
Affected
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| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 5.10 < 5.11.22 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.10 < 5.11.22" | en |
Affected
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| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 5.10 < 5.12.5 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.10 < 5.12.5" | en |
Affected
| ||||||
| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | >= 5.10 < 5.13 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.10 < 5.13" | en |
Affected
| ||||||
| Linux Search vendor "Linux" | Linux Kernel Search vendor "Linux" for product "Linux Kernel" | 5.9.10 Search vendor "Linux" for product "Linux Kernel" and version "5.9.10" | en |
Affected
| ||||||