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.
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.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
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 |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-15T05:55:13.248Z
Reserved: 2026-08-09T03:40:39.917Z
Link: CVE-2026-72292
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-15T06:22:01.377
Modified: 2026-08-15T06:22:01.377
Link: CVE-2026-72292
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.