arm64: kprobes: Allow reentering kprobes while single-stepping

{
  "id": "9cebc8e8e6fb60192192d5bb8a23c3d9ac860f3c402f93dee97d0425d92a52f9",
  "url": "https://osv.dev/vulnerability/CVE-2026-98888",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "arm64: kprobes: Allow reentering kprobes while single-stepping",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: arm64: kprobes: Allow reentering kprobes while single-stepping A kprobe can be hit while another kprobe is in KPROBE_HIT_SS state. This can happen when tracing or perf code runs from the debug exception path while the first kprobe is preparing or executing its out-of-line single-step instruction. Currently arm64 treats a kprobe hit in KPROBE_HIT_SS as unrecoverable, the same as a hit in KPROBE_REENTER. This is too strict. A hit in KPROBE_HIT_SS is still a one-level reentry and can be handled by saving the current kprobe state and setting up single-step for the new probe, just like reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. The truly unrecoverable case is hitting another kprobe while already in KPROBE_REENTER, because the reentry save area has already been consumed. Move KPROBE_HIT_SS to the recoverable reentry cases and leave KPROBE_REENTER as the unrecoverable nested reentry case. This change also requires saving saved_irqflag in struct prev_kprobe. When a nested kprobe calls kprobes_save_local_irqflag(), it overwrites kcb->saved_irqflag with the currently masked DAIF value, losing the outer kprobe's original DAIF state. Without this fix, when the outer kprobe's single-step finishes, kprobes_restore_local_irqflag() applies the wrong DAIF mask and leaves interrupts permanently disabled. Extend struct prev_kprobe with a saved_irqflag field and save/restore it alongside kp and status. This ensures the",
    "evidence": "osv:CVE-2026-98888",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.271",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.222",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.189",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.158",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.111",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.53",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98888",
      "aliases": [
        "CVE-2026-98888"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "2dd0e8d2d2a157dbc83295a78336c2217110f2f8"
                },
                {
                  "fixed": "bb0fe9121aa0824211aafa33c7d0151fd25ddb75"
                },
                {
                  "fixed": "f96a0606de6bcc8d937b80e6470fd7a174c17e26"
                },
                {
                  "fixed": "1f342b3e44c3035a837b53b217d816f7511c0d0a"
                },
                {
                  "fixed": "c8e84e292ed4cfc199824146da71bb4397b02a1f"
                },
                {
                  "fixed": "68774caca799e9695db56d426c69acebd041c2ed"
                },
                {
                  "fixed": "a21bf9cb893126e8d9730995708d0be5eb167652"
                },
                {
                  "fixed": "23f851ac0078a908bf3422d6467ebc1db5828c46"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98888.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "4.8.0"
                },
                {
                  "fixed": "5.10.271"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.222"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.189"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.158"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.111"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.53"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98888.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.383326241Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1f342b3e44c3035a837b53b217d816f7511c0d0a",
        "https://git.kernel.org/stable/c/23f851ac0078a908bf3422d6467ebc1db5828c46",
        "https://git.kernel.org/stable/c/68774caca799e9695db56d426c69acebd041c2ed",
        "https://git.kernel.org/stable/c/a21bf9cb893126e8d9730995708d0be5eb167652",
        "https://git.kernel.org/stable/c/bb0fe9121aa0824211aafa33c7d0151fd25ddb75",
        "https://git.kernel.org/stable/c/c8e84e292ed4cfc199824146da71bb4397b02a1f",
        "https://git.kernel.org/stable/c/f96a0606de6bcc8d937b80e6470fd7a174c17e26",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98888.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98888",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98888.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98888",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 505859,
  "published_at": "2026-10-23T11:37:46.984+00:00"
}