ghsa-w922-jv62-78r5
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
riscv: fix runtime constant support for nommu kernels
the __runtime_fixup_32 function does not handle the case where val is
zero correctly (as might occur when patching a nommu kernel and referring
to a physical address below the 4GiB boundary whose upper 32 bits are all
zero) because nothing in the existing logic prevents the code from taking
the else branch of both nop-checks and emitting two nop instructions.
This leaves random garbage in the register that is supposed to receive the upper 32 bits of the pointer instead of zero that when combined with the value for the lower 32 bits yields an invalid pointer and causes a kernel panic when that pointer is eventually accessed.
The author clearly considered the fact that if the lui is converted into
a nop that the second instruction needs to be adjusted to become an li
instead of an addi, hence introducing the addi_insn_mask variable, but
didn't follow that logic through fully to the case where the else branch
executes. To fix it just adjust the logic to ensure that the second else
branch is not taken if the first instruction will be patched to a nop.
{
"affected": [],
"aliases": [
"CVE-2025-38433"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-25T15:15:28Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: fix runtime constant support for nommu kernels\n\nthe `__runtime_fixup_32` function does not handle the case where `val` is\nzero correctly (as might occur when patching a nommu kernel and referring\nto a physical address below the 4GiB boundary whose upper 32 bits are all\nzero) because nothing in the existing logic prevents the code from taking\nthe `else` branch of both nop-checks and emitting two `nop` instructions.\n\nThis leaves random garbage in the register that is supposed to receive the\nupper 32 bits of the pointer instead of zero that when combined with the\nvalue for the lower 32 bits yields an invalid pointer and causes a kernel\npanic when that pointer is eventually accessed.\n\nThe author clearly considered the fact that if the `lui` is converted into\na `nop` that the second instruction needs to be adjusted to become an `li`\ninstead of an `addi`, hence introducing the `addi_insn_mask` variable, but\ndidn\u0027t follow that logic through fully to the case where the `else` branch\nexecutes. To fix it just adjust the logic to ensure that the second `else`\nbranch is not taken if the first instruction will be patched to a `nop`.",
"id": "GHSA-w922-jv62-78r5",
"modified": "2025-07-25T15:30:54Z",
"published": "2025-07-25T15:30:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38433"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0a24b00dcde83934a3cc13e4c6b775522903496b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8d90d9872edae7e78c3a12b98e239bfaa66f3639"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.