ghsa-c4vm-rj4p-m3c8
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix a sdiv overflow issue
Zac Ecob reported a problem where a bpf program may cause kernel crash due to the following error: Oops: divide error: 0000 [#1] PREEMPT SMP KASAN PTI
The failure is due to the below signed divide: LLONG_MIN/-1 where LLONG_MIN equals to -9,223,372,036,854,775,808. LLONG_MIN/-1 is supposed to give a positive number 9,223,372,036,854,775,808, but it is impossible since for 64-bit system, the maximum positive number is 9,223,372,036,854,775,807. On x86_64, LLONG_MIN/-1 will cause a kernel exception. On arm64, the result for LLONG_MIN/-1 is LLONG_MIN.
Further investigation found all the following sdiv/smod cases may trigger an exception when bpf program is running on x86_64 platform: - LLONG_MIN/-1 for 64bit operation - INT_MIN/-1 for 32bit operation - LLONG_MIN%-1 for 64bit operation - INT_MIN%-1 for 32bit operation where -1 can be an immediate or in a register.
On arm64, there are no exceptions: - LLONG_MIN/-1 = LLONG_MIN - INT_MIN/-1 = INT_MIN - LLONG_MIN%-1 = 0 - INT_MIN%-1 = 0 where -1 can be an immediate or in a register.
Insn patching is needed to handle the above cases and the patched codes produced results aligned with above arm64 result. The below are pseudo codes to handle sdiv/smod exceptions including both divisor -1 and divisor 0 and the divisor is stored in a register.
sdiv: tmp = rX tmp += 1 /* [-1, 0] -> [0, 1] if tmp >(unsigned) 1 goto L2 if tmp == 0 goto L1 rY = 0 L1: rY = -rY; goto L3 L2: rY /= rX L3:
smod: tmp = rX tmp += 1 /* [-1, 0] -> [0, 1] if tmp >(unsigned) 1 goto L1 if tmp == 1 (is64 ? goto L2 : goto L3) rY = 0; goto L2 L1: rY %= rX L2: goto L4 // only when !is64 L3: wY = wY // only when !is64 L4:
[1] https://lore.kernel.org/bpf/tPJLTEh7S_DxFEqAI2Ji5MBSoZVg7_G-Py2iaZpAaWtM961fFTWtsnlzwvTbzBzaUzwQAoNATXKUlt0LZOFgnDcIyKCswAnAGdUF3LBrhGQ=@protonmail.com/
{
"affected": [],
"aliases": [
"CVE-2024-49888"
],
"database_specific": {
"cwe_ids": [
"CWE-190"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-21T18:15:11Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix a sdiv overflow issue\n\nZac Ecob reported a problem where a bpf program may cause kernel crash due\nto the following error:\n Oops: divide error: 0000 [#1] PREEMPT SMP KASAN PTI\n\nThe failure is due to the below signed divide:\n LLONG_MIN/-1 where LLONG_MIN equals to -9,223,372,036,854,775,808.\nLLONG_MIN/-1 is supposed to give a positive number 9,223,372,036,854,775,808,\nbut it is impossible since for 64-bit system, the maximum positive\nnumber is 9,223,372,036,854,775,807. On x86_64, LLONG_MIN/-1 will\ncause a kernel exception. On arm64, the result for LLONG_MIN/-1 is\nLLONG_MIN.\n\nFurther investigation found all the following sdiv/smod cases may trigger\nan exception when bpf program is running on x86_64 platform:\n - LLONG_MIN/-1 for 64bit operation\n - INT_MIN/-1 for 32bit operation\n - LLONG_MIN%-1 for 64bit operation\n - INT_MIN%-1 for 32bit operation\nwhere -1 can be an immediate or in a register.\n\nOn arm64, there are no exceptions:\n - LLONG_MIN/-1 = LLONG_MIN\n - INT_MIN/-1 = INT_MIN\n - LLONG_MIN%-1 = 0\n - INT_MIN%-1 = 0\nwhere -1 can be an immediate or in a register.\n\nInsn patching is needed to handle the above cases and the patched codes\nproduced results aligned with above arm64 result. The below are pseudo\ncodes to handle sdiv/smod exceptions including both divisor -1 and divisor 0\nand the divisor is stored in a register.\n\nsdiv:\n tmp = rX\n tmp += 1 /* [-1, 0] -\u003e [0, 1]\n if tmp \u003e(unsigned) 1 goto L2\n if tmp == 0 goto L1\n rY = 0\n L1:\n rY = -rY;\n goto L3\n L2:\n rY /= rX\n L3:\n\nsmod:\n tmp = rX\n tmp += 1 /* [-1, 0] -\u003e [0, 1]\n if tmp \u003e(unsigned) 1 goto L1\n if tmp == 1 (is64 ? goto L2 : goto L3)\n rY = 0;\n goto L2\n L1:\n rY %= rX\n L2:\n goto L4 // only when !is64\n L3:\n wY = wY // only when !is64\n L4:\n\n [1] https://lore.kernel.org/bpf/tPJLTEh7S_DxFEqAI2Ji5MBSoZVg7_G-Py2iaZpAaWtM961fFTWtsnlzwvTbzBzaUzwQAoNATXKUlt0LZOFgnDcIyKCswAnAGdUF3LBrhGQ=@protonmail.com/",
"id": "GHSA-c4vm-rj4p-m3c8",
"modified": "2024-11-13T15:31:37Z",
"published": "2024-10-21T18:30:57Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-49888"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4902a6a0dc593c82055fc8c9ada371bafe26c9cc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7dd34d7b7dcf9309fc6224caf4dd5b35bedddcb7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d22e45a369afc7c28f11acfa5b5e8e478227ca5d"
}
],
"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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