{
  "cveId": "CVE-2021-47584",
  "url": "https://patchblox.com/security/cve/CVE-2021-47584",
  "summary": "CVE-2021-47584 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47584, released June 19, 2024. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  iocost: Fix divide-by-zero on donation from low...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  iocost: Fix divide-by-zero on donation from low hweight cgroup  The donation calculation logic assumes that the donor has non-zero after-donation hweight, so the lowest active hweight a donating cgroup can have is 2 so that it can donate 1 while keeping the other 1 for itself. Earlier, we only donated from cgroups with sizable surpluses so this condition was always true. However, with the precise donation algorithm implemented, f1de2439ec43 (\u0022blk-iocost: revamp donation amount determination\u0022) made the donation amount calculation exact enabling even low hweight cgroups to donate.  This means that in rare occasions, a cgroup with active hweight of 1 can enter donation calculation triggering the following warning and then a divide-by-zero oops.   WARNING: CPU: 4 PID: 0 at block/blk-iocost.c:1928 transfer_surpluses.cold\u002B0x0/0x53 [884/94867]  ...  RIP: 0010:transfer_surpluses.cold\u002B0x0/0x53  Code: 92 ff 48 c7 c7 28 d1 ab b5 65 48 8b 34 25 00 ae 01 00 48 81 c6 90 06 00 00 e8 8b 3f fe ff 48 c7 c0 ea ff ff ff e9 95 ff 92 ff \u003C0f\u003E 0b 48 c7 c7 30 da ab b5 e8 71 3f fe ff 4c 89 e8 4d 85 ed 74 0 4  ...  Call Trace:   \u003CIRQ\u003E   ioc_timer_fn\u002B0x1043/0x1390   call_timer_fn\u002B0xa1/0x2c0   __run_timers.part.0\u002B0x1ec/0x2e0   run_timer_softirq\u002B0x35/0x70  ...  iocg: invalid donation weights in /a/b: active=1 donating=1 after=0  Fix it by excluding cgroups w/ active hweight \u003C 2 from donating. Excluding these extreme low hweight donations shouldn\u0027t affect work conservation in any meaningful way.",
  "published": "2024-06-19T15:15:52Z",
  "severity": "medium",
  "cvss": 5.5,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.0025,
  "epssPercentile": 0.16398,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "5.15.15-1",
      "fix": "DEBIAN-CVE-2021-47584",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47584",
      "released": "2024-06-19T15:15:52Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "5.15.15-1",
      "fix": "DEBIAN-CVE-2021-47584",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47584",
      "released": "2024-06-19T15:15:52Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "5.15.15-1",
      "fix": "DEBIAN-CVE-2021-47584",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2021-47584",
      "released": "2024-06-19T15:15:52Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T13:06:02Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}