{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2024-35791",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2024-35791"
  ],
  "published": "2024-05-17T12:25:21Z",
  "summary": "KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region()\n\nDo the cache flush of converted pages in svm_register_enc_region() before\ndropping kvm->lock to fix use-after-free issues where region and/or its\narray of pages could be freed by a different task, e.g. if userspace has\n__unregister_enc_region_locked() already queued up for the region.\n\nNote, the \"obvious\" alternative of using local variables doesn't fully\nresolve the bug, as region->pages is also dynamically allocated.  I.e. the\nregion structure itself would be fine, but region->pages could be freed.\n\nFlushing multiple pages under kvm->lock is unfortunate, but the entire\nflow is a rare slow path, and the manual flush is only needed on CPUs that\nlack coherency for encrypted memory.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.84",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2024-35791"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2d13b79640b147bd77c34a5998533b2021a4122d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e126b508ed2e616d679d85fca2fbe77bb48bbdd7"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/4868c0ecdb6cfde7c70cf478c46e06bb9c7e5865"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/12f8e32a5a389a5d58afc67728c76e61beee1ad4"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f6d53d8a2617dd58c89171a6b9610c470ebda38a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5ef1d8c1ddbf696e47b226e11888eaf8d9e8e807"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T11:52:36Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerable code is reached only through the `KVM_MEMORY_ENCRYPT_REG_REGION`/`KVM_MEMORY_ENCRYPT_UNREG_REGION` ioctls on a local KVM VM file descriptor obtained from /dev/kvm. There is no remote or network-facing path to `sev_mem_enc_register_region()`.\nAC:L - The attacker controls both sides of the race, issuing the register and unregister ioctls from two threads it owns, and can widen the window arbitrarily by registering a large region since `sev_clflush_pages()` loops per page with `cond_resched()` after the lock is dropped. Nothing about winning the race depends on conditions outside the attacker's influence.\nPR:L - No capability check exists on the path \u2014 neither `kvm_arch_vm_ioctl()`'s `KVM_MEMORY_ENCRYPT_*_REGION` cases nor `sev_guest_init()` require CAP_SYS_ADMIN \u2014 so any local user with access to /dev/kvm (commonly granted via the `kvm` group or permissive device modes on virtualization hosts) can create an SEV VM and trigger the UAF.\nUI:N - The attacking process performs both ioctls itself; no action by any other user or victim process is needed.\nS:U - The attacker is host userspace (the VMM process) corrupting host kernel memory, so the vulnerable component and impacted component share the same security authority. This is not a guest-to-host escape, as the guest cannot issue these ioctls.\nC:H - The use-after-free reads a freed, sprayable kvmalloc'd `struct page *` array and then maps and flushes those attacker-influenceable pointers via `kmap_local_page()`, exposing arbitrary kernel/physical memory and enabling information disclosure once the freed slabs are reallocated.\nI:H - Two heap objects (`region` and `region->pages`) are used after being freed and can be reallocated with attacker-controlled contents, giving the heap-spray primitives typical of exploitable UAFs; `clflush_cache_range()` on a bogus mapping additionally acts on memory outside the intended range.\nA:H - Dereferencing freed `region->npages`/`region->pages` and calling `kmap_local_page()` on garbage `struct page` pointers reliably produces an oops or panic, taking the host kernel down."
    }
  }
}