IM
IronMonkey Threat Research

CVE-2024-35944 MEDIUM

Published: 2024-05-19 | Last Modified: 2026-05-12 | Status: Modified

Description

In the Linux kernel, the following vulnerability has been resolved: VMCI: Fix memcpy() run-time warning in dg_dispatch_as_host() Syzkaller hit 'WARNING in dg_dispatch_as_host' bug. memcpy: detected field-spanning write (size 56) of single field "&dg_info->msg" at drivers/misc/vmw_vmci/vmci_datagram.c:237 (size 24) WARNING: CPU: 0 PID: 1555 at drivers/misc/vmw_vmci/vmci_datagram.c:237 dg_dispatch_as_host+0x88e/0xa60 drivers/misc/vmw_vmci/vmci_datagram.c:237 Some code commentry, based on my understanding: 544 #define VMCI_DG_SIZE(_dg) (VMCI_DG_HEADERSIZE + (size_t)(_dg)->payload_size) /// This is 24 + payload_size memcpy(&dg_info->msg, dg, dg_size); Destination = dg_info->msg ---> this is a 24 byte structure(struct vmci_datagram) Source = dg --> this is a 24 byte structure (struct vmci_datagram) Size = dg_size = 24 + payload_size {payload_size = 56-24 =32} -- Syzkaller managed to set payload_size to 32. 35 struct delayed_datagram_info { 36 struct datagram_entry *entry; 37 struct work_struct work; 38 bool in_dg_host_queue; 39 /* msg and msg_payload must be together. */ 40 struct vmci_datagram msg; 41 u8 msg_payload[]; 42 }; So those extra bytes of payload are copied into msg_payload[], a run time warning is seen while fuzzing with Syzkaller. One possible way to fix the warning is to split the memcpy() into two parts -- one -- direct assignment of msg and second taking care of payload. Gustavo quoted: "Under FORTIFY_SOURCE we should not copy data across multiple members in a structure."

Additional Descriptions (1)

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: VMCI: corrigió la advertencia de tiempo de ejecución de memcpy() en dg_dispatch_as_host() Syzkaller presionó el error 'ADVERTENCIA en dg_dispatch_as_host'. memcpy: se detectó escritura que abarca todos los campos (tamaño 56) de un solo campo "&dg_info->msg" en drivers/misc/vmw_vmci/vmci_datagram.c:237 (tamaño 24) ADVERTENCIA: CPU: 0 PID: 1555 en drivers/misc/vmw_vmci /vmci_datagram.c:237 dg_dispatch_as_host+0x88e/0xa60 drivers/misc/vmw_vmci/vmci_datagram.c:237 Algunos comentarios de código, según tengo entendido: 544 #define VMCI_DG_SIZE(_dg) (VMCI_DG_HEADERSIZE + (size_t)(_dg)->payload_size ) /// Esto es 24 + payload_size memcpy(&dg_info->msg, dg, dg_size); Destino = dg_info->msg ---> esta es una estructura de 24 bytes (struct vmci_datagram) Fuente = dg --> esta es una estructura de 24 bytes (struct vmci_datagram) Tamaño = dg_size = 24 + payload_size {payload_size = 56-24 = 32} -- Syzkaller logró establecer payload_size en 32. 35 struct delay_datagram_info { 36 struct datagram_entry *entry; 37 struct work_struct work; 38 bool in_dg_host_queue; 39 /* msg y msg_payload deben estar juntos. */ 40 struct vmci_datagram mensaje; 41 u8 msg_payload[]; 42}; Entonces, esos bytes adicionales de payload se copian en msg_payload[], se ve una advertencia de tiempo de ejecución mientras se utiliza Syzkaller. Una forma posible de solucionar la advertencia es dividir memcpy() en dos partes: una, asignación directa del mensaje y la segunda, encargada del payload. Gustavo citó: "Bajo FORTIFY_SOURCE no debemos copiar datos entre varios miembros de una estructura".

CVSS Metrics

Base Score: 5.5 (MEDIUM)

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack VectorLOCAL
Attack ComplexityLOW
Privileges RequiredLOW
User InteractionNONE
ScopeUNCHANGED
Confidentiality ImpactNONE
Integrity ImpactNONE
Availability ImpactHIGH

Source: [email protected]

Type: Primary

Exploitability Score: 1.8

Impact Score: 3.6

Weaknesses

Source Type Description
[email protected] Primary
en NVD-CWE-noinfo

Affected Products

Vendor Product Version Update Type
linux linux_kernel * <built-in method update of dict object at 0x7fd3686e7c40> Operating System
linux linux_kernel * <built-in method update of dict object at 0x7fd3686e6940> Operating System
linux linux_kernel * <built-in method update of dict object at 0x7fd36afa4440> Operating System
linux linux_kernel * <built-in method update of dict object at 0x7fd36a0edac0> Operating System
linux linux_kernel * <built-in method update of dict object at 0x7fd3686e5840> Operating System
linux linux_kernel * <built-in method update of dict object at 0x7fd3686e4cc0> Operating System
linux linux_kernel * <built-in method update of dict object at 0x7fd31b63c3c0> Operating System
debian debian_linux 10.0 <built-in method update of dict object at 0x7fd31b63c880> Operating System

Affected Configurations

Operator: OR

Vulnerable CPE
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Yes cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

Operator: OR

Vulnerable CPE
Yes cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

References