{
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    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2021-47584",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-05-24T15:11:00.731Z",
        "datePublished": "2024-06-19T14:53:50.119Z",
        "dateUpdated": "2026-05-11T13:57:22.259Z"
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                "dateUpdated": "2026-05-11T13:57:22.259Z"
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                    "lang": "en",
                    "value": "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 <0f> 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  <IRQ>\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 < 2 from donating. Excluding\nthese extreme low hweight donations shouldn't affect work conservation in\nany meaningful way."
                }
            ],
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                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "block/blk-iocost.c"
                    ],
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                            "version": "f1de2439ec43b74764f2a26e3a310b24407e3bde",
                            "lessThan": "a7c80674538f15f85d68138240aae440b8039519",
                            "status": "affected",
                            "versionType": "git"
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                            "lessThan": "3a1a4eb574178c21241a6200f4785572e661c472",
                            "status": "affected",
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                            "lessThan": "edaa26334c117a584add6053f48d63a988d25a6e",
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                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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                            "status": "affected"
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                            "version": "0",
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                            "versionType": "semver"
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                            "version": "5.10.88",
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                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
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                    "url": "https://git.kernel.org/stable/c/edaa26334c117a584add6053f48d63a988d25a6e"
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            "title": "iocost: Fix divide-by-zero on donation from low hweight cgroup",
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