Linux Kernel CVE-2024-36910

The uio_hv_generic driver provides userspace I/O access to VMBus devices - a Hyper-V-specific virtual bus used in Linux VMs running on Microsoft Hyper-V and Azure. In Confidential Computing (CoCo) VM environments, guest memory pages are individually managed as either encrypted (private, inaccessible to host) or decrypted (shared with host). The kernel functions set_memory_encrypted() and set_memory_decrypted() transition pages between these states. The vulnerability, classified as CWE-200 (Exposure of Sensitive Information), arises because the driver did not consult the 'decrypted' field in the GPADL (Guest Physical Address Descriptor List) structure before freeing memory. When the untrusted host causes set_memory_decrypted() to return an error, the resulting memory state is indeterminate - the pages may still be host-accessible (decrypted/shared) but the driver proceeds to free them to the guest allocator as if they were private. The fix introduces a conditional check of gpadl->decrypted before releasing the pages. CPE data confirms the affected product is cpe:2.3:o:linux:linux_kernel across multiple stable branches, with 6.9-rc1 through 6.9-rc3 explicitly enumerated, indicating the patch landed before the 6.9 final release.