In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Initialize KVM_S390_GET_CMMA_BITS memory kvm_s390_get_cmma_bits() allocates its output buffer with vmalloc(), which does not zero the returned pages: values = vmalloc(args->count); In the non-peek (migration) path, dat_get_cmma() reports a byte count spanning from the first to the last dirty page, but __dat_get_cmma_pte() writes values[gfn - start] only for pages whose CMMA dirty bit is set. The walk uses DAT_WALK_IGN_HOLES, so clean and unmapped pages that lie between two dirty pages within the reported span are visited but never store their byte. Those gaps (up to KVM_S390_MAX_BIT_DISTANCE pages each) stay uninitialized yet fall inside [0, count) and are copied out by copy_to_user(), disclosing stale kernel memory to user space. Before the switch to the new gmap implementation the buffer was fully populated for every gfn in the span, so no uninitialized bytes were exposed; the dirty-only walk introduced the leak. Use vzalloc() so the gaps read back as zero.
History

Sat, 15 Aug 2026 06:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Initialize KVM_S390_GET_CMMA_BITS memory kvm_s390_get_cmma_bits() allocates its output buffer with vmalloc(), which does not zero the returned pages: values = vmalloc(args->count); In the non-peek (migration) path, dat_get_cmma() reports a byte count spanning from the first to the last dirty page, but __dat_get_cmma_pte() writes values[gfn - start] only for pages whose CMMA dirty bit is set. The walk uses DAT_WALK_IGN_HOLES, so clean and unmapped pages that lie between two dirty pages within the reported span are visited but never store their byte. Those gaps (up to KVM_S390_MAX_BIT_DISTANCE pages each) stay uninitialized yet fall inside [0, count) and are copied out by copy_to_user(), disclosing stale kernel memory to user space. Before the switch to the new gmap implementation the buffer was fully populated for every gfn in the span, so no uninitialized bytes were exposed; the dirty-only walk introduced the leak. Use vzalloc() so the gaps read back as zero.
Title KVM: s390: Initialize KVM_S390_GET_CMMA_BITS memory
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-15T05:55:13.248Z

Reserved: 2026-08-09T03:40:39.917Z

Link: CVE-2026-72292

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-15T06:22:01.377

Modified: 2026-08-15T06:22:01.377

Link: CVE-2026-72292

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.