CVE-2021-47640
- Source
- https://cve.org/CVERecord?id=CVE-2021-47640
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47640.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2021-47640
- Downstream
- Published
- 2025-02-26T06:37:05.780Z
- Modified
- 2026-03-15T22:43:17.023197Z
- Severity
-
- 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
- Summary
- [none]
- Details
-
In the Linux kernel, the following vulnerability has been resolved:
powerpc/kasan: Fix early region not updated correctly
The shadow's page table is not updated when PTERPNSHIFT is 24 and PAGE_SHIFT is 12. It not only causes false positives but also false negative as shown the following text.
Fix it by bringing the logic of kasanearlyshadowpageentry here.
1. False Positive:
BUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50 Write of size 16 at addr f57f3be0 by task swapper/0/1
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1 Call Trace: [c80d1c20] [c07fe7b8] dumpstacklvl+0x4c/0x6c (unreliable) [c80d1c40] [c02ff668] printaddressdescription.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasanreport+0x1ec/0x200 [c80d1cb0] [c0300b20] kasancheckrange+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpualloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmemcachecreate+0xfc/0x570 [c80d1d70] [c0283d64] kmemcachecreateusercopy+0x274/0x3e0 [c80d1db0] [c2036580] initsd+0xc4/0x1d0 [c80d1de0] [c00044a0] dooneinitcall+0xc0/0x33c [c80d1eb0] [c2001624] kernelinitfreeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernelinit+0x24/0x170 [c80d1f10] [c001b26c] retfromkernelthread+0x5c/0x64
Memory state around the buggy address: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
2. False Negative (with KASAN tests):
Before fix: ok 45 - kmallocdoublekzfree # vmallocoob: EXPECTATION FAILED at lib/testkasan.c:1039 KASAN failure expected in "((volatile char *)area)[3100]", but none occurred not ok 46 - vmalloc_oob not ok 1 - kasan
================================================================== After fix: ok 1 - kasan
- References
-
- https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3
- https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d
- https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6
- https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115
- https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068
- https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2
Affected packages
Git /
Database specific
source
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47640.json"
unresolved_ranges
[
{
"events": [
{
"introduced": "5.4"
},
{
"fixed": "5.4.189"
}
]
},
{
"events": [
{
"introduced": "5.5"
},
{
"fixed": "5.10.110"
}
]
},
{
"events": [
{
"introduced": "5.11"
},
{
"fixed": "5.15.33"
}
]
},
{
"events": [
{
"introduced": "5.16"
},
{
"fixed": "5.16.19"
}
]
},
{
"events": [
{
"introduced": "5.17"
},
{
"fixed": "5.17.2"
}
]
}
]