github - ghsa-9777-6rgr-2wc6

ghsa-9777-6rgr-2wc6

Vulnerability from github

Published

2024-06-19 15:30

Modified

2024-08-19 21:35

Severity ?

5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Details

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 ("blk-iocost: revamp donation amount determination") 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+0x0/0x53 [884/94867] ... RIP: 0010:transfer_surpluses.cold+0x0/0x53 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 <0f> 0b 48 c7 c7 30 da ab b5 e8 71 3f fe ff 4c 89 e8 4d 85 ed 74 0 4 ... Call Trace: ioc_timer_fn+0x1043/0x1390 call_timer_fn+0xa1/0x2c0 __run_timers.part.0+0x1ec/0x2e0 run_timer_softirq+0x35/0x70 ... iocg: invalid donation weights in /a/b: active=1 donating=1 after=0

Fix it by excluding cgroups w/ active hweight < 2 from donating. Excluding these extreme low hweight donations shouldn't affect work conservation in any meaningful way.

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{
  "affected": [],
  "aliases": [
    "CVE-2021-47584"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-369"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-06-19T15:15:52Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\niocost: Fix divide-by-zero on donation from low hweight cgroup\n\nThe donation calculation logic assumes that the donor has non-zero\nafter-donation hweight, so the lowest active hweight a donating cgroup can\nhave is 2 so that it can donate 1 while keeping the other 1 for itself.\nEarlier, we only donated from cgroups with sizable surpluses so this\ncondition was always true. However, with the precise donation algorithm\nimplemented, f1de2439ec43 (\"blk-iocost: revamp donation amount\ndetermination\") made the donation amount calculation exact enabling even low\nhweight cgroups to donate.\n\nThis means that in rare occasions, a cgroup with active hweight of 1 can\nenter donation calculation triggering the following warning and then a\ndivide-by-zero oops.\n\n WARNING: CPU: 4 PID: 0 at block/blk-iocost.c:1928 transfer_surpluses.cold+0x0/0x53 [884/94867]\n ...\n RIP: 0010:transfer_surpluses.cold+0x0/0x53\n 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\n4\n ...\n Call Trace:\n  \u003cIRQ\u003e\n  ioc_timer_fn+0x1043/0x1390\n  call_timer_fn+0xa1/0x2c0\n  __run_timers.part.0+0x1ec/0x2e0\n  run_timer_softirq+0x35/0x70\n ...\n iocg: invalid donation weights in /a/b: active=1 donating=1 after=0\n\nFix it by excluding cgroups w/ active hweight \u003c 2 from donating. Excluding\nthese extreme low hweight donations shouldn\u0027t affect work conservation in\nany meaningful way.",
  "id": "GHSA-9777-6rgr-2wc6",
  "modified": "2024-08-19T21:35:07Z",
  "published": "2024-06-19T15:30:55Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47584"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3a1a4eb574178c21241a6200f4785572e661c472"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a7c80674538f15f85d68138240aae440b8039519"
    },
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      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

cve-2021-47584

Vulnerability from cvelistv5

Published

2024-06-19 14:53

Modified

2024-11-04 12:08

Severity ?

Summary

iocost: Fix divide-by-zero on donation from low hweight cgroup

References

▼	URL	Tags
	https://git.kernel.org/stable/c/a7c80674538f15f85d68138240aae440b8039519
	https://git.kernel.org/stable/c/3a1a4eb574178c21241a6200f4785572e661c472
	https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e

Impacted products

Vendor

Product

Version

▼

Linux

Version: f1de2439ec43
Version: f1de2439ec43
Version: f1de2439ec43

Linux

Version: 5.10

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
Confirmed: The vulnerability is confirmed from an analyst perspective.
Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
Patched: This vulnerability was successfully patched by the user reporting the sighting.
Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
Not confirmed: The user expresses doubt about the veracity of the vulnerability.
Not patched: This vulnerability was not successfully patched by the user reporting the sighting.

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