Linux Kernel
CVE-2024-35944
MEDIUM
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
1DescriptionCVE.org
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."
AnalysisAI
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. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
Technical ContextAI
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." Affected products include: Linux Linux Kernel, Debian Debian Linux.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
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