GHSA-CPM2-25VC-F276
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-15 06:32In the Linux kernel, the following vulnerability has been resolved:
MIPS: DEC: Ensure 32-bit stack location for o32 prom_printf()
In 64-bit configurations calling any firmware entry points from a kernel thread other than the initial one will result in a situation where the stack has been placed in the XKPHYS 64-bit memory segment.
Consequently the stack pointer is no longer a 32-bit value and when the 32-bit firmware code called uses 32-bit ALU operations to manipulate the stack pointer, the calculated result is incorrect (in fact in the 64-bit MIPS ISA almost all 32-bit ALU operations will produce an unpredictable result when executed on 64-bit data) and control goes astray.
This may happen when no final console driver has been enabled in the configuration and consequently the initial console continues being used late into bootstrap, or with an upcoming change that will switch the zs driver to use a platform device, which in turn will make the console handover happen only after other kernel threads have already been started, and the kernel will hang at:
pid_max: default: 32768 minimum: 301
or somewhat later, but always before:
cblist_init_generic: Setting adjustable number of callback queues.
has been printed.
It seems that only the prom_printf() entry point is affected. Of all the other entry points wired only rex_slot_address() and rex_gettcinfo() are called from a kernel thread other than the initial one, specifically kernel_init(), and they are leaf functions that do no business with the stack, having worked with no issue ever since 64-bit support was added for the platform back in 2002.
To address this issue then, arrange for the stack to be switched in the o32 wrapper as required for prom_printf() only, by supplying call_o32() with a pointer to a chunk of initdata space, which is placed in the CKSEG0 32-bit compatibility segment, observing that prom_printf() is only called from console output handler and therefore with the console lock held, implying no need for this code to be reentrant.
Other firmware entry points may be called with interrupts enabled and no lock held, and may therefore require that call_o32() be reentrant. They trigger no issue at this point and "if it ain't broke, don't fix it," so just leave them alone.
{
"affected": [],
"aliases": [
"CVE-2026-72215"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:21:40Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nMIPS: DEC: Ensure 32-bit stack location for o32 prom_printf()\n\nIn 64-bit configurations calling any firmware entry points from a kernel\nthread other than the initial one will result in a situation where the\nstack has been placed in the XKPHYS 64-bit memory segment.\n\nConsequently the stack pointer is no longer a 32-bit value and when the\n32-bit firmware code called uses 32-bit ALU operations to manipulate the\nstack pointer, the calculated result is incorrect (in fact in the 64-bit\nMIPS ISA almost all 32-bit ALU operations will produce an unpredictable\nresult when executed on 64-bit data) and control goes astray.\n\nThis may happen when no final console driver has been enabled in the\nconfiguration and consequently the initial console continues being used\nlate into bootstrap, or with an upcoming change that will switch the zs\ndriver to use a platform device, which in turn will make the console\nhandover happen only after other kernel threads have already been\nstarted, and the kernel will hang at:\n\n pid_max: default: 32768 minimum: 301\n\nor somewhat later, but always before:\n\n cblist_init_generic: Setting adjustable number of callback queues.\n\nhas been printed.\n\nIt seems that only the prom_printf() entry point is affected. Of all\nthe other entry points wired only rex_slot_address() and rex_gettcinfo()\nare called from a kernel thread other than the initial one, specifically\nkernel_init(), and they are leaf functions that do no business with the\nstack, having worked with no issue ever since 64-bit support was added\nfor the platform back in 2002.\n\nTo address this issue then, arrange for the stack to be switched in the\no32 wrapper as required for prom_printf() only, by supplying call_o32()\nwith a pointer to a chunk of initdata space, which is placed in the\nCKSEG0 32-bit compatibility segment, observing that prom_printf() is\nonly called from console output handler and therefore with the console\nlock held, implying no need for this code to be reentrant.\n\nOther firmware entry points may be called with interrupts enabled and no\nlock held, and may therefore require that call_o32() be reentrant. They\ntrigger no issue at this point and \"if it ain\u0027t broke, don\u0027t fix it,\" so\njust leave them alone.",
"id": "GHSA-cpm2-25vc-f276",
"modified": "2026-08-15T06:32:16Z",
"published": "2026-08-15T06:32:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72215"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1ed18b5c3be9657fe288fa4dae0bef2470598683"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/27857db30c98583e12dd8d939ba2370bce08a5be"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3394757c5d3970ab36d2aafa6dd40952b43f0d16"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3ae86630b94f72bf4012c6322f81f622dc4fdf24"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5ff79e8bdc75db51e30298a75939e2308e7658e0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9cd4a8ed12d2a6313592e43c14cca5eca6717bee"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d3fd2d358df0ca712183509cbbed6a16bde1d17e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d828bca84311e278093e60b2864a54f4bbb0c2ad"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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