CVE-2024-35944: VMCI: Fix memcpy() run-time warning in dg_dispatch_as_host()
First published: Sun May 19 2024(Updated: )
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."
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| debian/linux | 5.10.223-1 6.1.106-3 6.1.99-1 6.10.6-1 6.10.9-1 |
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Reference Links
- https://git.kernel.org/stable/c/130b0cd064874e0d0f58e18fb00e6f3993e90c74
- https://git.kernel.org/stable/c/19b070fefd0d024af3daa7329cbc0d00de5302ec
- https://git.kernel.org/stable/c/491a1eb07c2bd8841d63cb5263455e185be5866f
- https://git.kernel.org/stable/c/ad78c5047dc4076d0b3c4fad4f42ffe9c86e8100
- https://git.kernel.org/stable/c/dae70a57565686f16089737adb8ac64471570f73
- https://git.kernel.org/stable/c/e87bb99d2df6512d8ee37a5d63d2ca9a39a8c051
- https://git.kernel.org/stable/c/f15eca95138b3d4ec17b63c3c1937b0aa0d3624b
- https://git.kernel.org/stable/c/feacd430b42bbfa9ab3ed9e4f38b86c43e348c75
- https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html
- https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html
- https://launchpad.net/bugs/cve/CVE-2024-35944
- https://git.kernel.org/linus/19b070fefd0d024af3daa7329cbc0d00de5302ec
- https://security-tracker.debian.org/tracker/CVE-2024-35944
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-35944
- https://nvd.nist.gov/vuln/detail/CVE-2024-35944
- https://ubuntu.com/security/CVE-2024-35944
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