ghsa-9777-6rgr-2wc6
Vulnerability from github
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:
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.
{
"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"
},
{
"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"
}
]
}