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FKIE_CVE-2026-93182

Vulnerability from fkie_nvd - Published: 2026-09-17 17:18 - Updated: 2026-09-17 17:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: sched/fair: Fix overflow in update_tg_cfs_runnable() A divide-by-zero crash is observed when running hackbench: [14697.488452] CPU: 112 UID: 0 PID: 124791 Comm: hackbench Not tainted 7.1.0-rc2+ [14697.492627] RIP: 0010:propagate_entity_load_avg+0x35f/0x3e0 [14697.506799] <TASK> [14697.507411] __dequeue_task+0x2b4/0xc70 [14697.508677] dequeue_task_fair+0x36/0x370 [14697.509047] dequeue_task+0x101/0x2f0 [14697.509426] __schedule+0x1b1/0x1a00 [14697.510868] anon_pipe_read+0x3da/0x450 [14697.511400] vfs_read+0x361/0x390 [14697.512053] __x64_sys_read+0x19/0x30 The divide-by-zero happens here: if (scale_load_down(gcfs_rq->load.weight)) { load_sum = div_u64(gcfs_rq->avg.load_sum, scale_load_down(gcfs_rq->load.weight)); } gcfs_rq->load.weight is an insane large value and is truncated to the lower 32 bits by div_u64, which happen to be 0. Using AI for investigation, the cause is a u32 overflow in update_tg_cfs_runnable(), and flat pickup became a victim when using tg_tasks(): u32 new_sum, divider; ... new_sum = se->avg.runnable_avg * divider; <-- boom The following sequence shows how this triggers the crash: propagate_entity_load_avg() update_tg_cfs_runnable() # u32 overflow corrupts runnable_sum __update_load_avg_cfs_rq() ___update_load_avg() # computes insane runnable_avg update_tg_load_avg() # propagates to tg->runnable_avg update_cfs_group() calc_concur_shares() tg_tasks() # long-to-int truncation, negative nr reweight_entity() # corrupted se->load.weight update_load_add() # corrupted cfs_rq->load.weight propagate_entity_load_avg() update_tg_cfs_load() div_u64() # divide-by-zero Fix by widening new_sum from u32 to u64 (no need to force tg_tasks() to return unsigned long after this fix)
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/18fdd0978ec3dda0ff6865cd273e47e022180710
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/39d707097a0820c6e87eff4195f0940e8ff1147e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4f166adb5cb0525d9e32d45729fd8f28c80acbee
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7cc237e3bc1733928313d2462b413ae441b0eef3
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f94e62d21faad5e244d0874598a4d0ebbc0ea405
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/fair.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "39d707097a0820c6e87eff4195f0940e8ff1147e",
              "status": "affected",
              "version": "95246d1ec80b8d19d882cd8eb7ad094e63b41bb8",
              "versionType": "git"
            },
            {
              "lessThan": "69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75",
              "status": "affected",
              "version": "95246d1ec80b8d19d882cd8eb7ad094e63b41bb8",
              "versionType": "git"
            },
            {
              "lessThan": "7cc237e3bc1733928313d2462b413ae441b0eef3",
              "status": "affected",
              "version": "95246d1ec80b8d19d882cd8eb7ad094e63b41bb8",
              "versionType": "git"
            },
            {
              "lessThan": "18fdd0978ec3dda0ff6865cd273e47e022180710",
              "status": "affected",
              "version": "95246d1ec80b8d19d882cd8eb7ad094e63b41bb8",
              "versionType": "git"
            },
            {
              "lessThan": "f94e62d21faad5e244d0874598a4d0ebbc0ea405",
              "status": "affected",
              "version": "95246d1ec80b8d19d882cd8eb7ad094e63b41bb8",
              "versionType": "git"
            },
            {
              "lessThan": "4f166adb5cb0525d9e32d45729fd8f28c80acbee",
              "status": "affected",
              "version": "95246d1ec80b8d19d882cd8eb7ad094e63b41bb8",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/sched/fair.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.17"
            },
            {
              "lessThan": "5.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Fix overflow in update_tg_cfs_runnable()\n\nA divide-by-zero crash is observed when running hackbench:\n\n   [14697.488452] CPU: 112 UID: 0 PID: 124791 Comm: hackbench Not tainted 7.1.0-rc2+\n   [14697.492627] RIP: 0010:propagate_entity_load_avg+0x35f/0x3e0\n   [14697.506799]  \u003cTASK\u003e\n   [14697.507411]  __dequeue_task+0x2b4/0xc70\n   [14697.508677]  dequeue_task_fair+0x36/0x370\n   [14697.509047]  dequeue_task+0x101/0x2f0\n   [14697.509426]  __schedule+0x1b1/0x1a00\n   [14697.510868]  anon_pipe_read+0x3da/0x450\n   [14697.511400]  vfs_read+0x361/0x390\n   [14697.512053]  __x64_sys_read+0x19/0x30\n\nThe divide-by-zero happens here:\n\n  if (scale_load_down(gcfs_rq-\u003eload.weight)) {\n           load_sum = div_u64(gcfs_rq-\u003eavg.load_sum,\n                              scale_load_down(gcfs_rq-\u003eload.weight));\n  }\n\ngcfs_rq-\u003eload.weight is an insane large value and is truncated\nto the lower 32 bits by div_u64, which happen to be 0.\n\nUsing AI for investigation, the cause is a u32 overflow in\nupdate_tg_cfs_runnable(), and flat pickup became a victim when using\ntg_tasks():\n\n   u32 new_sum, divider;\n   ...\n   new_sum = se-\u003eavg.runnable_avg * divider; \u003c-- boom\n\nThe following sequence shows how this triggers the crash:\n\n   propagate_entity_load_avg()\n     update_tg_cfs_runnable()     # u32 overflow corrupts runnable_sum\n\n   __update_load_avg_cfs_rq()\n     ___update_load_avg()         # computes insane runnable_avg\n   update_tg_load_avg()           # propagates to tg-\u003erunnable_avg\n\n   update_cfs_group()\n     calc_concur_shares()\n       tg_tasks()                 # long-to-int truncation, negative nr\n     reweight_entity()            # corrupted se-\u003eload.weight\n       update_load_add()          # corrupted cfs_rq-\u003eload.weight\n\n   propagate_entity_load_avg()\n     update_tg_cfs_load()\n       div_u64()                  # divide-by-zero\n\nFix by widening new_sum from u32 to u64 (no need to force tg_tasks()\nto return unsigned long after this fix)"
    }
  ],
  "id": "CVE-2026-93182",
  "lastModified": "2026-09-17T17:18:14.153",
  "metrics": {},
  "published": "2026-09-17T17:18:14.153",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/18fdd0978ec3dda0ff6865cd273e47e022180710"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/39d707097a0820c6e87eff4195f0940e8ff1147e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4f166adb5cb0525d9e32d45729fd8f28c80acbee"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7cc237e3bc1733928313d2462b413ae441b0eef3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f94e62d21faad5e244d0874598a4d0ebbc0ea405"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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