CyberRota Analysis
AI-GeneratedThe vulnerability affects the Linux kernel's KVM component, specifically in the `kvm_s390_get_cmma_bits()` function, which improperly allocates memory without zeroing it, leading to potential disclosure of uninitialized kernel memory to user space. This can expose sensitive data residing in memory gaps between dirty pages during migration operations. Organizations using Linux systems with KVM, particularly those in environments handling sensitive data, should prioritize addressing this vulnerability to mitigate risks of information leakage.
Original NVD 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.