// For flags

CVE-2024-26885

bpf: Fix DEVMAP_HASH overflow check on 32-bit arches

Severity Score

7.8
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track*
*SSVC
Descriptions

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix DEVMAP_HASH overflow check on 32-bit arches

The devmap code allocates a number hash buckets equal to the next power
of two of the max_entries value provided when creating the map. When
rounding up to the next power of two, the 32-bit variable storing the
number of buckets can overflow, and the code checks for overflow by
checking if the truncated 32-bit value is equal to 0. However, on 32-bit
arches the rounding up itself can overflow mid-way through, because it
ends up doing a left-shift of 32 bits on an unsigned long value. If the
size of an unsigned long is four bytes, this is undefined behaviour, so
there is no guarantee that we'll end up with a nice and tidy 0-value at
the end.

Syzbot managed to turn this into a crash on arm32 by creating a
DEVMAP_HASH with max_entries > 0x80000000 and then trying to update it.
Fix this by moving the overflow check to before the rounding up
operation.

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: bpf: corrige la verificación de desbordamiento de DEVMAP_HASH en arcos de 32 bits. El código devmap asigna un número de depósitos de hash igual a la siguiente potencia de dos del valor max_entries proporcionado al crear el mapa. Al redondear a la siguiente potencia de dos, la variable de 32 bits que almacena el número de depósitos puede desbordarse, y el código verifica el desbordamiento comprobando si el valor truncado de 32 bits es igual a 0. Sin embargo, en arcos de 32 bits el redondeo hacia arriba puede desbordarse a mitad de camino, porque termina haciendo un desplazamiento hacia la izquierda de 32 bits en un valor largo sin signo. Si el tamaño de un largo sin firmar es de cuatro bytes, este es un comportamiento indefinido, por lo que no hay garantía de que terminemos con un valor 0 agradable y ordenado al final. Syzbot logró convertir esto en un bloqueo en arm32 creando un DEVMAP_HASH con max_entries > 0x80000000 y luego intentando actualizarlo. Solucione este problema moviendo la verificación de desbordamiento antes de la operación de redondeo.

*Credits: N/A
CVSS Scores
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
* Common Vulnerability Scoring System
SSVC
  • Decision:Track*
Exploitation
None
Automatable
No
Tech. Impact
Total
* Organization's Worst-case Scenario
Timeline
  • 2024-02-19 CVE Reserved
  • 2024-04-17 CVE Published
  • 2024-04-30 EPSS Updated
  • 2024-12-19 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
CAPEC
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"
>= 5.4 < 5.4.285
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.4.285"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 5.10.214
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.10.214"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 5.10.227
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.10.227"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 5.15.153
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.15.153"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 6.1.83
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 6.1.83"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 6.6.23
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 6.6.23"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 6.7.11
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 6.7.11"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 6.8.2
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 6.8.2"
en
Affected
Linux
Search vendor "Linux"
Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
>= 5.4 < 6.9
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 6.9"
en
Affected