CVE-2024-35944

Summary

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 Software

VendorProductVersion RangeStatus
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < e87bb99d2df6512d8ee37a5d63d2ca9a39a8c051affected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < f15eca95138b3d4ec17b63c3c1937b0aa0d3624baffected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < ad78c5047dc4076d0b3c4fad4f42ffe9c86e8100affected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < 130b0cd064874e0d0f58e18fb00e6f3993e90c74affected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < feacd430b42bbfa9ab3ed9e4f38b86c43e348c75affected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < dae70a57565686f16089737adb8ac64471570f73affected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < 491a1eb07c2bd8841d63cb5263455e185be5866faffected
LinuxLinuxa110b7ebb9c674a2b591af2780dd512ad0198d50 < 19b070fefd0d024af3daa7329cbc0d00de5302ecaffected
LinuxLinux3.9affected
LinuxLinux0 < 3.9unaffected
LinuxLinux4.19.312 <= 4.19.*unaffected
LinuxLinux5.4.274 <= 5.4.*unaffected
LinuxLinux5.10.215 <= 5.10.*unaffected
LinuxLinux5.15.155 <= 5.15.*unaffected
LinuxLinux6.1.86 <= 6.1.*unaffected
LinuxLinux6.6.27 <= 6.6.*unaffected
LinuxLinux6.8.6 <= 6.8.*unaffected
LinuxLinux6.9 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

CVE Program Container

Additional References

Additional References

References