CVE-2026-64248 (GCVE-0-2026-64248)
Vulnerability from cvelistv5
Published
2026-07-24 15:31
Modified
2026-08-17 04:51
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: MIPS: smp: report dying CPU to RCU in stop_this_cpu() smp_send_stop() parks all secondary CPUs in stop_this_cpu(). The function marks the CPU offline for the scheduler via set_cpu_online(false) but never informs RCU, so RCU keeps expecting a quiescent state from CPUs that are now spinning forever with interrupts disabled. As long as nothing waits for an RCU grace period after smp_send_stop() this is harmless, which is why it went unnoticed. Since commit 91840be8f710 ("irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT") however, irq_work_sync() calls synchronize_rcu() on architectures without an irq_work self-IPI, i.e. where arch_irq_work_has_interrupt() returns false. That is the asm-generic default used by MIPS. Any irq_work_sync() issued in the reboot/shutdown path after smp_send_stop() then blocks on a grace period that can never complete, hanging the reboot: WARNING: CPU: 0 PID: 15 at kernel/irq_work.c:144 irq_work_queue_on ... rcu: INFO: rcu_sched detected stalls on CPUs/tasks: rcu: Offline CPU 1 blocking current GP. rcu: Offline CPU 2 blocking current GP. rcu: Offline CPU 3 blocking current GP. This issue was noticed on several Realtek MIPS switch SoCs (MIPS interAptiv) and came up during kernel bump downstream in OpenWrt from 6.18.33 to 6.18.34, after the backport of the patch to the 6.18 stable branch. The patch also has been backported all the way back to 6.1. Call rcutree_report_cpu_dead() once interrupts are disabled, mirroring the generic CPU-hotplug offline path, so RCU stops waiting on the parked CPUs and grace periods can still complete. MIPS shuts down all CPUs here without going through the CPU-hotplug mechanism, so this report is not otherwise issued. Reporting a dying CPU to RCU outside the regular hotplug offline path is not unprecedented: arm64 does the same in cpu_die_early(). There it is an exception for a CPU that was coming online and is aborting bringup, rather than the default shutdown action as on MIPS.
References
Impacted products
Vendor Product Version
Linux Linux Version: 2dc79362302922cb18f35e262712b5e58de65442
Version: eef4f71b46a9929ac33e968538c9dd5d96a02460
Version: 684a78183c54c23e70d1cba320f7fc184604210b
Version: 18c0456ea2615b1a743a6db739c74411c3b42bc6
Version: 91840be8f710370607f949a627e070896faeddb8
Version: 91840be8f710370607f949a627e070896faeddb8
Version: 81b582784518196eff1050212a046bc29d3a05dd
Version: 6.1.175   ≤
Version: 6.6.142   ≤
Version: 6.12.92   ≤
Version: 6.18.34   ≤
Version: 7.0.11   ≤
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/mips/kernel/smp.c"
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "7.2",
              "versionType": "original_commit_for_fix"
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          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "negate": false,
              "operator": "OR"
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          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nMIPS: smp: report dying CPU to RCU in stop_this_cpu()\n\nsmp_send_stop() parks all secondary CPUs in stop_this_cpu(). The function\nmarks the CPU offline for the scheduler via set_cpu_online(false) but\nnever informs RCU, so RCU keeps expecting a quiescent state from CPUs\nthat are now spinning forever with interrupts disabled.\n\nAs long as nothing waits for an RCU grace period after smp_send_stop()\nthis is harmless, which is why it went unnoticed. Since commit\n91840be8f710 (\"irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT\")\nhowever, irq_work_sync() calls synchronize_rcu() on architectures without\nan irq_work self-IPI, i.e. where arch_irq_work_has_interrupt() returns\nfalse. That is the asm-generic default used by MIPS. Any irq_work_sync()\nissued in the reboot/shutdown path after smp_send_stop() then blocks on\na grace period that can never complete, hanging the reboot:\n\n  WARNING: CPU: 0 PID: 15 at kernel/irq_work.c:144 irq_work_queue_on\n  ...\n  rcu: INFO: rcu_sched detected stalls on CPUs/tasks:\n  rcu: Offline CPU 1 blocking current GP.\n  rcu: Offline CPU 2 blocking current GP.\n  rcu: Offline CPU 3 blocking current GP.\n\nThis issue was noticed on several Realtek MIPS switch SoCs (MIPS\ninterAptiv) and came up during kernel bump downstream in OpenWrt from\n6.18.33 to 6.18.34, after the backport of the patch to the 6.18 stable\nbranch. The patch also has been backported all the way back to 6.1.\n\nCall rcutree_report_cpu_dead() once interrupts are disabled, mirroring the\ngeneric CPU-hotplug offline path, so RCU stops waiting on the parked CPUs\nand grace periods can still complete. MIPS shuts down all CPUs here\nwithout going through the CPU-hotplug mechanism, so this report is not\notherwise issued. Reporting a dying CPU to RCU outside the regular hotplug\noffline path is not unprecedented: arm64 does the same in cpu_die_early().\nThere it is an exception for a CPU that was coming online and is aborting\nbringup, rather than the default shutdown action as on MIPS."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:59.618Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f8a1ef884013dc99f712d3eb75624c7cd3fd94f6"
        },
        {
          "url": "https://git.kernel.org/stable/c/e1919d026706544cb6e7251ec06e908edd6f34ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/6eda71977ee11c222f8ad4cae4d18d50448e56f4"
        },
        {
          "url": "https://git.kernel.org/stable/c/f9b57a0015c241274651f4b36627f56b1b5a8651"
        },
        {
          "url": "https://git.kernel.org/stable/c/9fef09df42df55ab819b285ea892e0fc1b95a9c4"
        },
        {
          "url": "https://git.kernel.org/stable/c/9f3f3bdc6d9dac1a5a8262ee7ad0f2ff1527a7e7"
        }
      ],
      "title": "MIPS: smp: report dying CPU to RCU in stop_this_cpu()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64248",
    "datePublished": "2026-07-24T15:31:15.892Z",
    "dateReserved": "2026-07-19T15:36:31.772Z",
    "dateUpdated": "2026-08-17T04:51:59.618Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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