ghsa-mhcq-hvgj-xm2h
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
x86: fix user address masking non-canonical speculation issue
It turns out that AMD has a "Meltdown Lite(tm)" issue with non-canonical accesses in kernel space. And so using just the high bit to decide whether an access is in user space or kernel space ends up with the good old "leak speculative data" if you have the right gadget using the result:
CVE-2020-12965 “Transient Execution of Non-Canonical Accesses“
Now, the kernel surrounds the access with a STAC/CLAC pair, and those instructions end up serializing execution on older Zen architectures, which closes the speculation window.
But that was true only up until Zen 5, which renames the AC bit [1]. That improves performance of STAC/CLAC a lot, but also means that the speculation window is now open.
Note that this affects not just the new address masking, but also the regular valid_user_address() check used by access_ok(), and the asm version of the sign bit check in the get_user() helpers.
It does not affect put_user() or clear_user() variants, since there's no speculative result to be used in a gadget for those operations.
{
"affected": [],
"aliases": [
"CVE-2024-50102"
],
"database_specific": {
"cwe_ids": [
"CWE-203"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-11-05T18:15:13Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86: fix user address masking non-canonical speculation issue\n\nIt turns out that AMD has a \"Meltdown Lite(tm)\" issue with non-canonical\naccesses in kernel space. And so using just the high bit to decide\nwhether an access is in user space or kernel space ends up with the good\nold \"leak speculative data\" if you have the right gadget using the\nresult:\n\n CVE-2020-12965 \u201cTransient Execution of Non-Canonical Accesses\u201c\n\nNow, the kernel surrounds the access with a STAC/CLAC pair, and those\ninstructions end up serializing execution on older Zen architectures,\nwhich closes the speculation window.\n\nBut that was true only up until Zen 5, which renames the AC bit [1].\nThat improves performance of STAC/CLAC a lot, but also means that the\nspeculation window is now open.\n\nNote that this affects not just the new address masking, but also the\nregular valid_user_address() check used by access_ok(), and the asm\nversion of the sign bit check in the get_user() helpers.\n\nIt does not affect put_user() or clear_user() variants, since there\u0027s no\nspeculative result to be used in a gadget for those operations.",
"id": "GHSA-mhcq-hvgj-xm2h",
"modified": "2024-11-12T15:30:32Z",
"published": "2024-11-05T18:32:12Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-50102"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/291313693677a345d4f50aae3c68e28b469f601e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/86e6b1547b3d013bc392adf775b89318441403c2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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- 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.