Release Date: | 2024-05-19 |
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.'
See more information about CVE-2024-35944 from MITRE CVE dictionary and NIST NVD
NOTE: The following CVSS v3.1 metrics and score provided are preliminary and subject to review.
Base Score: | 5.5 | CVSS Vector: | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
Attack Vector: | Local network | Attack Complexity: | Low |
Privileges Required: | Low | User Interaction: | None |
Scope: | Unchanged | Confidentiality Impact: | None |
Integrity Impact: | None | Availability Impact: | High |
Platform | Errata | Release Date |
Oracle Linux version 6 (kernel-uek) | ELSA-2024-12606 | 2024-09-02 |
Oracle Linux version 7 (kernel-uek) | ELSA-2024-12606 | 2024-09-02 |
Oracle Linux version 8 (kernel) | ELSA-2024-7000 | 2024-09-24 |
Oracle VM version 3 (kernel-uek) | OVMSA-2024-0011 | 2024-09-03 |
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