GHSA-FG62-2Q3C-3W5H
Vulnerability from github – Published: 2026-09-24 18:31 – Updated: 2026-09-25 06:30In the Linux kernel, the following vulnerability has been resolved:
nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry
The hand-rolled seqcount-like protocol in nfsd_nl_rpc_status_get_dumpit() is missing a read memory barrier (smp_rmb) before its second counter check. The standard kernel read_seqcount_retry() includes smp_rmb() to ensure that all data reads complete before the counter is re-checked.
Without this barrier, on weakly-ordered architectures (ARM, POWER), the CPU may reorder field reads past the second counter check, making the retry logic ineffective: it could observe a consistent counter pair while reading fields that have been concurrently modified by the writer.
Add smp_rmb() before the second counter check to order the field reads ahead of it, matching the barrier semantics of the standard seqcount read-side. The begin-side smp_load_acquire() already pairs with the smp_store_release() in nfsd_dispatch(); with the smp_rmb() now ordering the field reads, the retry check no longer needs acquire semantics and reads the counter with a plain READ_ONCE(), as read_seqcount_retry() does.
[ cel: Use READ_ONCE instead of smp_load_acquire() ]
{
"affected": [],
"aliases": [
"CVE-2026-93229"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-24T16:17:18Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: add missing read barrier to rpc_status_get dumpit seqcount retry\n\nThe hand-rolled seqcount-like protocol in nfsd_nl_rpc_status_get_dumpit()\nis missing a read memory barrier (smp_rmb) before its second counter\ncheck. The standard kernel read_seqcount_retry() includes smp_rmb()\nto ensure that all data reads complete before the counter is re-checked.\n\nWithout this barrier, on weakly-ordered architectures (ARM, POWER),\nthe CPU may reorder field reads past the second counter check, making\nthe retry logic ineffective: it could observe a consistent counter pair\nwhile reading fields that have been concurrently modified by the writer.\n\nAdd smp_rmb() before the second counter check to order the field reads\nahead of it, matching the barrier semantics of the standard seqcount\nread-side. The begin-side smp_load_acquire() already pairs with the\nsmp_store_release() in nfsd_dispatch(); with the smp_rmb() now ordering\nthe field reads, the retry check no longer needs acquire semantics and\nreads the counter with a plain READ_ONCE(), as read_seqcount_retry()\ndoes.\n\n[ cel: Use READ_ONCE instead of smp_load_acquire() ]",
"id": "GHSA-fg62-2q3c-3w5h",
"modified": "2026-09-25T06:30:28Z",
"published": "2026-09-24T18:31:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93229"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1aea0482b98ecd7d0249204665f2ad4ad517f66b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9b5f6475006cd8e3b5b99b8eb3cd74dbb1ce9df8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a71f161a857117e8e0264deb7d14fff5c98adcf5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f501f2f4ec1d2dfe39e21c98630314074a9b30b0"
}
],
"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:H",
"type": "CVSS_V3"
}
]
}
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