CVE-2021-47390 (GCVE-0-2021-47390)

Vulnerability from cvelistv5 – Published: 2024-05-21 15:03 – Updated: 2026-08-05 08:47
VLAI
Title
KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect()
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect() KASAN reports the following issue: BUG: KASAN: stack-out-of-bounds in kvm_make_vcpus_request_mask+0x174/0x440 [kvm] Read of size 8 at addr ffffc9001364f638 by task qemu-kvm/4798 CPU: 0 PID: 4798 Comm: qemu-kvm Tainted: G X --------- --- Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM0081C 07/13/2020 Call Trace: dump_stack+0xa5/0xe6 print_address_description.constprop.0+0x18/0x130 ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] __kasan_report.cold+0x7f/0x114 ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] kasan_report+0x38/0x50 kasan_check_range+0xf5/0x1d0 kvm_make_vcpus_request_mask+0x174/0x440 [kvm] kvm_make_scan_ioapic_request_mask+0x84/0xc0 [kvm] ? kvm_arch_exit+0x110/0x110 [kvm] ? sched_clock+0x5/0x10 ioapic_write_indirect+0x59f/0x9e0 [kvm] ? static_obj+0xc0/0xc0 ? __lock_acquired+0x1d2/0x8c0 ? kvm_ioapic_eoi_inject_work+0x120/0x120 [kvm] The problem appears to be that 'vcpu_bitmap' is allocated as a single long on stack and it should really be KVM_MAX_VCPUS long. We also seem to clear the lower 16 bits of it with bitmap_zero() for no particular reason (my guess would be that 'bitmap' and 'vcpu_bitmap' variables in kvm_bitmap_or_dest_vcpus() caused the confusion: while the later is indeed 16-bit long, the later should accommodate all possible vCPUs).
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-06-17 17:37 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6856 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7ee30bc132c683d06a6d9e360e39e483e3990708 , < bebabb76ad9acca8858e0371e102fb60d708e25b (git)
Affected: 7ee30bc132c683d06a6d9e360e39e483e3990708 , < 99a9e9b80f19fc63be005a33d76211dd23114792 (git)
Affected: 7ee30bc132c683d06a6d9e360e39e483e3990708 , < 2f9b68f57c6278c322793a06063181deded0ad69 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.5
Unaffected: 0 , < 5.5 (semver)
Unaffected: 5.10.71 , ≤ 5.10.* (semver)
Unaffected: 5.14.10 , ≤ 5.14.* (semver)
Unaffected: 5.15 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-125"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:58:31+00:00",
      "cve": "CVE-2021-47390",
      "id": "CVE-2021-47390",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_affected": "42",
      "product_status:known_not_affected": "156",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47390.json",
      "version": "3"
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    "vulnrichment": {
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              "dateUpdated": "2024-08-04T05:39:59.812Z",
              "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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            ],
            "title": "CVE Program Container"
          },
          {
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                "other": {
                  "content": {
                    "id": "CVE-2021-47390",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
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                    "role": "CISA Coordinator",
                    "timestamp": "2024-06-17T17:37:17.652949Z",
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              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
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              "product": "Linux",
              "programFiles": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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              "versions": [
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                  "status": "unaffected",
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                  "versionType": "original_commit_for_fix"
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                    },
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            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect()\n\nKASAN reports the following issue:\n\n BUG: KASAN: stack-out-of-bounds in kvm_make_vcpus_request_mask+0x174/0x440 [kvm]\n Read of size 8 at addr ffffc9001364f638 by task qemu-kvm/4798\n\n CPU: 0 PID: 4798 Comm: qemu-kvm Tainted: G               X --------- ---\n Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM0081C 07/13/2020\n Call Trace:\n  dump_stack+0xa5/0xe6\n  print_address_description.constprop.0+0x18/0x130\n  ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm]\n  __kasan_report.cold+0x7f/0x114\n  ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm]\n  kasan_report+0x38/0x50\n  kasan_check_range+0xf5/0x1d0\n  kvm_make_vcpus_request_mask+0x174/0x440 [kvm]\n  kvm_make_scan_ioapic_request_mask+0x84/0xc0 [kvm]\n  ? kvm_arch_exit+0x110/0x110 [kvm]\n  ? sched_clock+0x5/0x10\n  ioapic_write_indirect+0x59f/0x9e0 [kvm]\n  ? static_obj+0xc0/0xc0\n  ? __lock_acquired+0x1d2/0x8c0\n  ? kvm_ioapic_eoi_inject_work+0x120/0x120 [kvm]\n\nThe problem appears to be that \u0027vcpu_bitmap\u0027 is allocated as a single long\non stack and it should really be KVM_MAX_VCPUS long. We also seem to clear\nthe lower 16 bits of it with bitmap_zero() for no particular reason (my\nguess would be that \u0027bitmap\u0027 and \u0027vcpu_bitmap\u0027 variables in\nkvm_bitmap_or_dest_vcpus() caused the confusion: while the later is indeed\n16-bit long, the later should accommodate all possible vCPUs)."
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                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
                "version": "3.1"
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                  "lang": "en",
                  "value": "AV:L - The bug is reached when a guest writes the in-kernel IOAPIC MMIO window (0xfec00000), causing a KVM MMIO exit into ioapic_mmio_write \u2192 ioapic_write_indirect on the host; this is a local hypervisor/guest interface, not a network protocol path.\nAC:L - A guest (or VMM user who creates the VM) can reliably trigger the path by writing an IOAPIC redirect entry with FIXED delivery mode; the undersized bitmap is always over-read, and with \u226565 vCPUs the attacker-controlled dest can also force out-of-bounds __set_bit writes with no race or uncontrolled condition.\nPR:L - Exploitation needs only the ability to run a KVM guest that uses the in-kernel irqchip\u2014typically an unprivileged kvm-group user on /dev/kvm, or a cloud tenant controlling their guest OS\u2014not real host root/CAP_SYS_ADMIN.\nUI:N - No victim action is required; the attacker triggers the vulnerable IOAPIC write path directly from guest code or their own VMM once the VM exists.\nS:C - A malicious guest corrupts host-kernel stack memory in KVM\u2019s IOAPIC emulation, crossing the guest/host security boundary and enabling a potential VM escape affecting the host and other tenants.\nC:H - kvm_make_vcpus_request_mask performs a stack out-of-bounds read of the undersized vcpu_bitmap across KVM_MAX_VCPUS bits (~128 bytes), and stack corruption from the related OOB write can be leveraged for further host memory disclosure.\nI:H - kvm_bitmap_or_dest_vcpus uses __set_bit() on vcpu_idx values that can exceed the single unsigned long (bits \u226564), writing past the stack allocation toward higher stack addresses and enabling host memory corruption / control-flow hijacking.\nA:H - The out-of-bounds stack access can oops/panic the host kernel (as shown by the KASAN report in qemu-kvm), so availability impact on the host is high."
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              "url": "https://git.kernel.org/stable/c/2f9b68f57c6278c322793a06063181deded0ad69"
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        "assignerShortName": "Linux",
        "cveId": "CVE-2021-47390",
        "datePublished": "2024-05-21T15:03:48.883Z",
        "dateReserved": "2024-05-21T14:58:30.813Z",
        "dateUpdated": "2026-08-05T08:47:35.643Z",
        "state": "PUBLISHED"
      },
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      "dataVersion": "5.2"
    }
  }
}



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