ghsa-r9xv-hg83-5rcx
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
powerpc/tm: Fix more userspace r13 corruption
Commit cf13435b730a ("powerpc/tm: Fix userspace r13 corruption") fixes a problem in treclaim where a SLB miss can occur on the thread_struct->ckpt_regs while SCRATCH0 is live with the saved user r13 value, clobbering it with the kernel r13 and ultimately resulting in kernel r13 being stored in ckpt_regs.
There is an equivalent problem in trechkpt where the user r13 value is loaded into r13 from chkpt_regs to be recheckpointed, but a SLB miss could occur on ckpt_regs accesses after that, which will result in r13 being clobbered with a kernel value and that will get recheckpointed and then restored to user registers.
The same memory page is accessed right before this critical window where a SLB miss could cause corruption, so hitting the bug requires the SLB entry be removed within a small window of instructions, which is possible if a SLB related MCE hits there. PAPR also permits the hypervisor to discard this SLB entry (because slb_shadow->persistent is only set to SLB_NUM_BOLTED) although it's not known whether any implementations would do this (KVM does not). So this is an extremely unlikely bug, only found by inspection.
Fix this by also storing user r13 in a temporary location on the kernel stack and don't change the r13 register from kernel r13 until the RI=0 critical section that does not fault.
The SCRATCH0 change is not strictly part of the fix, it's only used in the RI=0 section so it does not have the same problem as the previous SCRATCH0 bug.
{
"affected": [],
"aliases": [
"CVE-2022-49164"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-26T07:00:53Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/tm: Fix more userspace r13 corruption\n\nCommit cf13435b730a (\"powerpc/tm: Fix userspace r13 corruption\") fixes a\nproblem in treclaim where a SLB miss can occur on the\nthread_struct-\u003eckpt_regs while SCRATCH0 is live with the saved user r13\nvalue, clobbering it with the kernel r13 and ultimately resulting in\nkernel r13 being stored in ckpt_regs.\n\nThere is an equivalent problem in trechkpt where the user r13 value is\nloaded into r13 from chkpt_regs to be recheckpointed, but a SLB miss\ncould occur on ckpt_regs accesses after that, which will result in r13\nbeing clobbered with a kernel value and that will get recheckpointed and\nthen restored to user registers.\n\nThe same memory page is accessed right before this critical window where\na SLB miss could cause corruption, so hitting the bug requires the SLB\nentry be removed within a small window of instructions, which is\npossible if a SLB related MCE hits there. PAPR also permits the\nhypervisor to discard this SLB entry (because slb_shadow-\u003epersistent is\nonly set to SLB_NUM_BOLTED) although it\u0027s not known whether any\nimplementations would do this (KVM does not). So this is an extremely\nunlikely bug, only found by inspection.\n\nFix this by also storing user r13 in a temporary location on the kernel\nstack and don\u0027t change the r13 register from kernel r13 until the RI=0\ncritical section that does not fault.\n\nThe SCRATCH0 change is not strictly part of the fix, it\u0027s only used in\nthe RI=0 section so it does not have the same problem as the previous\nSCRATCH0 bug.",
"id": "GHSA-r9xv-hg83-5rcx",
"modified": "2025-09-23T15:31:07Z",
"published": "2025-09-23T15:31:07Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-49164"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5dce84f475d13b773a1a4c823581cab25044d86a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/73d8082c90f17dfba57cad4ca94db5cae323f1b1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9d71165d3934e607070c4e48458c0cf161b1baea"
}
],
"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"
}
]
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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