CVE-2025-68810 (GCVE-0-2025-68810)
Vulnerability from cvelistv5
Published
2026-01-13 15:29
Modified
2026-02-09 08:33
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot Reject attempts to disable KVM_MEM_GUEST_MEMFD on a memslot that was initially created with a guest_memfd binding, as KVM doesn't support toggling KVM_MEM_GUEST_MEMFD on existing memslots. KVM prevents enabling KVM_MEM_GUEST_MEMFD, but doesn't prevent clearing the flag. Failure to reject the new memslot results in a use-after-free due to KVM not unbinding from the guest_memfd instance. Unbinding on a FLAGS_ONLY change is easy enough, and can/will be done as a hardening measure (in anticipation of KVM supporting dirty logging on guest_memfd at some point), but fixing the use-after-free would only address the immediate symptom. ================================================================== BUG: KASAN: slab-use-after-free in kvm_gmem_release+0x362/0x400 [kvm] Write of size 8 at addr ffff8881111ae908 by task repro/745 CPU: 7 UID: 1000 PID: 745 Comm: repro Not tainted 6.18.0-rc6-115d5de2eef3-next-kasan #3 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dump_stack_lvl+0x51/0x60 print_report+0xcb/0x5c0 kasan_report+0xb4/0xe0 kvm_gmem_release+0x362/0x400 [kvm] __fput+0x2fa/0x9d0 task_work_run+0x12c/0x200 do_exit+0x6ae/0x2100 do_group_exit+0xa8/0x230 __x64_sys_exit_group+0x3a/0x50 x64_sys_call+0x737/0x740 do_syscall_64+0x5b/0x900 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f581f2eac31 </TASK> Allocated by task 745 on cpu 6 at 9.746971s: kasan_save_stack+0x20/0x40 kasan_save_track+0x13/0x50 __kasan_kmalloc+0x77/0x90 kvm_set_memory_region.part.0+0x652/0x1110 [kvm] kvm_vm_ioctl+0x14b0/0x3290 [kvm] __x64_sys_ioctl+0x129/0x1a0 do_syscall_64+0x5b/0x900 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Freed by task 745 on cpu 6 at 9.747467s: kasan_save_stack+0x20/0x40 kasan_save_track+0x13/0x50 __kasan_save_free_info+0x37/0x50 __kasan_slab_free+0x3b/0x60 kfree+0xf5/0x440 kvm_set_memslot+0x3c2/0x1160 [kvm] kvm_set_memory_region.part.0+0x86a/0x1110 [kvm] kvm_vm_ioctl+0x14b0/0x3290 [kvm] __x64_sys_ioctl+0x129/0x1a0 do_syscall_64+0x5b/0x900 entry_SYSCALL_64_after_hwframe+0x4b/0x53
References
Impacted products
Vendor Product Version
Linux Linux Version: a7800aa80ea4d5356b8474c2302812e9d4926fa6
Version: a7800aa80ea4d5356b8474c2302812e9d4926fa6
Version: a7800aa80ea4d5356b8474c2302812e9d4926fa6
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "virt/kvm/kvm_main.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "89dbbe6ff323fc34659621a577fe0af913f47386",
              "status": "affected",
              "version": "a7800aa80ea4d5356b8474c2302812e9d4926fa6",
              "versionType": "git"
            },
            {
              "lessThan": "cb51bef465d8ec60a968507330e01020e35dc127",
              "status": "affected",
              "version": "a7800aa80ea4d5356b8474c2302812e9d4926fa6",
              "versionType": "git"
            },
            {
              "lessThan": "9935df5333aa503a18de5071f53762b65c783c4c",
              "status": "affected",
              "version": "a7800aa80ea4d5356b8474c2302812e9d4926fa6",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "virt/kvm/kvm_main.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.64",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.64",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.3",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot\n\nReject attempts to disable KVM_MEM_GUEST_MEMFD on a memslot that was\ninitially created with a guest_memfd binding, as KVM doesn\u0027t support\ntoggling KVM_MEM_GUEST_MEMFD on existing memslots.  KVM prevents enabling\nKVM_MEM_GUEST_MEMFD, but doesn\u0027t prevent clearing the flag.\n\nFailure to reject the new memslot results in a use-after-free due to KVM\nnot unbinding from the guest_memfd instance.  Unbinding on a FLAGS_ONLY\nchange is easy enough, and can/will be done as a hardening measure (in\nanticipation of KVM supporting dirty logging on guest_memfd at some point),\nbut fixing the use-after-free would only address the immediate symptom.\n\n  ==================================================================\n  BUG: KASAN: slab-use-after-free in kvm_gmem_release+0x362/0x400 [kvm]\n  Write of size 8 at addr ffff8881111ae908 by task repro/745\n\n  CPU: 7 UID: 1000 PID: 745 Comm: repro Not tainted 6.18.0-rc6-115d5de2eef3-next-kasan #3 NONE\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  Call Trace:\n   \u003cTASK\u003e\n   dump_stack_lvl+0x51/0x60\n   print_report+0xcb/0x5c0\n   kasan_report+0xb4/0xe0\n   kvm_gmem_release+0x362/0x400 [kvm]\n   __fput+0x2fa/0x9d0\n   task_work_run+0x12c/0x200\n   do_exit+0x6ae/0x2100\n   do_group_exit+0xa8/0x230\n   __x64_sys_exit_group+0x3a/0x50\n   x64_sys_call+0x737/0x740\n   do_syscall_64+0x5b/0x900\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x7f581f2eac31\n   \u003c/TASK\u003e\n\n  Allocated by task 745 on cpu 6 at 9.746971s:\n   kasan_save_stack+0x20/0x40\n   kasan_save_track+0x13/0x50\n   __kasan_kmalloc+0x77/0x90\n   kvm_set_memory_region.part.0+0x652/0x1110 [kvm]\n   kvm_vm_ioctl+0x14b0/0x3290 [kvm]\n   __x64_sys_ioctl+0x129/0x1a0\n   do_syscall_64+0x5b/0x900\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\n  Freed by task 745 on cpu 6 at 9.747467s:\n   kasan_save_stack+0x20/0x40\n   kasan_save_track+0x13/0x50\n   __kasan_save_free_info+0x37/0x50\n   __kasan_slab_free+0x3b/0x60\n   kfree+0xf5/0x440\n   kvm_set_memslot+0x3c2/0x1160 [kvm]\n   kvm_set_memory_region.part.0+0x86a/0x1110 [kvm]\n   kvm_vm_ioctl+0x14b0/0x3290 [kvm]\n   __x64_sys_ioctl+0x129/0x1a0\n   do_syscall_64+0x5b/0x900\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-09T08:33:59.332Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/89dbbe6ff323fc34659621a577fe0af913f47386"
        },
        {
          "url": "https://git.kernel.org/stable/c/cb51bef465d8ec60a968507330e01020e35dc127"
        },
        {
          "url": "https://git.kernel.org/stable/c/9935df5333aa503a18de5071f53762b65c783c4c"
        }
      ],
      "title": "KVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68810",
    "datePublished": "2026-01-13T15:29:16.475Z",
    "dateReserved": "2025-12-24T10:30:51.047Z",
    "dateUpdated": "2026-02-09T08:33:59.332Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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