GHSA-CWPJ-WXFP-CRC5
Vulnerability from github – Published: 2024-04-02 09:30 – Updated: 2025-03-17 18:31In the Linux kernel, the following vulnerability has been resolved:
x86/lib: Revert to _ASM_EXTABLE_UA() for {get,put}_user() fixups
During memory error injection test on kernels >= v6.4, the kernel panics like below. However, this issue couldn't be reproduced on kernels <= v6.3.
mce: [Hardware Error]: CPU 296: Machine Check Exception: f Bank 1: bd80000000100134 mce: [Hardware Error]: RIP 10: {__get_user_nocheck_4+0x6/0x20} mce: [Hardware Error]: TSC 411a93533ed ADDR 346a8730040 MISC 86 mce: [Hardware Error]: PROCESSOR 0:a06d0 TIME 1706000767 SOCKET 1 APIC 211 microcode 80001490 mce: [Hardware Error]: Run the above through 'mcelog --ascii' mce: [Hardware Error]: Machine check: Data load in unrecoverable area of kernel Kernel panic - not syncing: Fatal local machine check
The MCA code can recover from an in-kernel #MC if the fixup type is EX_TYPE_UACCESS, explicitly indicating that the kernel is attempting to access userspace memory. However, if the fixup type is EX_TYPE_DEFAULT the only thing that is raised for an in-kernel #MC is a panic.
ex_handler_uaccess() would warn if users gave a non-canonical addresses (with bit 63 clear) to {get, put}_user(), which was unexpected.
Therefore, commit
b19b74bc99b1 ("x86/mm: Rework address range check in get_user() and put_user()")
replaced _ASM_EXTABLE_UA() with _ASM_EXTABLE() for {get, put}_user() fixups. However, the new fixup type EX_TYPE_DEFAULT results in a panic.
Commit
6014bc27561f ("x86-64: make access_ok() independent of LAM")
added the check gp_fault_address_ok() right before the WARN_ONCE() in ex_handler_uaccess() to not warn about non-canonical user addresses due to LAM.
With that in place, revert back to _ASM_EXTABLE_UA() for {get,put}_user() exception fixups in order to be able to handle in-kernel MCEs correctly again.
[ bp: Massage commit message. ]
{
"affected": [],
"aliases": [
"CVE-2024-26674"
],
"database_specific": {
"cwe_ids": [
"CWE-787"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-04-02T07:15:44Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/lib: Revert to _ASM_EXTABLE_UA() for {get,put}_user() fixups\n\nDuring memory error injection test on kernels \u003e= v6.4, the kernel panics\nlike below. However, this issue couldn\u0027t be reproduced on kernels \u003c= v6.3.\n\n mce: [Hardware Error]: CPU 296: Machine Check Exception: f Bank 1: bd80000000100134\n mce: [Hardware Error]: RIP 10:\u003cffffffff821b9776\u003e {__get_user_nocheck_4+0x6/0x20}\n mce: [Hardware Error]: TSC 411a93533ed ADDR 346a8730040 MISC 86\n mce: [Hardware Error]: PROCESSOR 0:a06d0 TIME 1706000767 SOCKET 1 APIC 211 microcode 80001490\n mce: [Hardware Error]: Run the above through \u0027mcelog --ascii\u0027\n mce: [Hardware Error]: Machine check: Data load in unrecoverable area of kernel\n Kernel panic - not syncing: Fatal local machine check\n\nThe MCA code can recover from an in-kernel #MC if the fixup type is\nEX_TYPE_UACCESS, explicitly indicating that the kernel is attempting to\naccess userspace memory. However, if the fixup type is EX_TYPE_DEFAULT\nthe only thing that is raised for an in-kernel #MC is a panic.\n\nex_handler_uaccess() would warn if users gave a non-canonical addresses\n(with bit 63 clear) to {get, put}_user(), which was unexpected.\n\nTherefore, commit\n\n b19b74bc99b1 (\"x86/mm: Rework address range check in get_user() and put_user()\")\n\nreplaced _ASM_EXTABLE_UA() with _ASM_EXTABLE() for {get, put}_user()\nfixups. However, the new fixup type EX_TYPE_DEFAULT results in a panic.\n\nCommit\n\n 6014bc27561f (\"x86-64: make access_ok() independent of LAM\")\n\nadded the check gp_fault_address_ok() right before the WARN_ONCE() in\nex_handler_uaccess() to not warn about non-canonical user addresses due\nto LAM.\n\nWith that in place, revert back to _ASM_EXTABLE_UA() for {get,put}_user()\nexception fixups in order to be able to handle in-kernel MCEs correctly\nagain.\n\n [ bp: Massage commit message. ]",
"id": "GHSA-cwpj-wxfp-crc5",
"modified": "2025-03-17T18:31:38Z",
"published": "2024-04-02T09:30:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26674"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2aed1b6c33afd8599d01c6532bbecb829480a674"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2da241c5ed78d0978228a1150735539fe1a60eca"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8eed4e00a370b37b4e5985ed983dccedd555ea9d"
}
],
"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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