GHSA-XW74-J5C3-43CH
Vulnerability from github – Published: 2026-09-17 18:32 – Updated: 2026-09-17 18:32In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix mmap_lock deadlock on arena lock failure
Reported by the Sashiko AI review.
arena_vm_fault() returns VM_FAULT_RETRY when it can't take arena->spinlock, but it never took mmap_lock. The fault path assumes a VM_FAULT_RETRY handler already dropped mmap_lock and re-takes it on the retry, so mmap_lock gets taken twice and can deadlock:
do_user_addr_fault()
{
fault = handle_mm_fault(...); // calls arena_vm_fault()
if (fault & VM_FAULT_RETRY)
goto retry; // re-locks mmap_lock
mmap_read_unlock(mm);
}
Return VM_FAULT_SIGBUS instead, for two reasons:
-
We could keep VM_FAULT_RETRY, but then we'd have to drop the fault lock first and cap the retry ourselves, the way __folio_lock_or_retry() does.
-
A failed raw_res_spin_lock_irqsave() already means a possible deadlock was detected, so retrying just hits the same lock again.
So returning VM_FAULT_RETRY here is overkill.
{
"affected": [],
"aliases": [
"CVE-2026-90342"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:32Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix mmap_lock deadlock on arena lock failure\n\nReported by the Sashiko AI review.\n\narena_vm_fault() returns VM_FAULT_RETRY when it can\u0027t take\narena-\u003espinlock, but it never took mmap_lock. The fault path assumes a\nVM_FAULT_RETRY handler already dropped mmap_lock and re-takes it on the\nretry, so mmap_lock gets taken twice and can deadlock:\n\n\tdo_user_addr_fault()\n\t{\n\t\tfault = handle_mm_fault(...); // calls arena_vm_fault()\n\t\tif (fault \u0026 VM_FAULT_RETRY)\n\t\t\tgoto retry; // re-locks mmap_lock\n\t\tmmap_read_unlock(mm);\n\t}\n\nReturn VM_FAULT_SIGBUS instead, for two reasons:\n\n1. We could keep VM_FAULT_RETRY, but then we\u0027d have to drop the fault\n lock first and cap the retry ourselves, the way __folio_lock_or_retry()\n does.\n\n2. A failed raw_res_spin_lock_irqsave() already means a possible deadlock\n was detected, so retrying just hits the same lock again.\n\nSo returning VM_FAULT_RETRY here is overkill.",
"id": "GHSA-xw74-j5c3-43ch",
"modified": "2026-09-17T18:32:01Z",
"published": "2026-09-17T18:32:01Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90342"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0b10b945479c954393d62ee3229d2f224a4ca91c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/af8087f16714f7620c4db3e732baaa1b2337948f"
}
],
"schema_version": "1.4.0",
"severity": []
}
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