CVE-2026-98530 (GCVE-0-2026-98530)
Vulnerability from cvelistv5
Published
2026-10-18 15:17
Modified
2026-10-19 09:21
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: kprobes: Fix permanent hang when flushing the kprobe optimizer Writing 0 to /proc/sys/debug/kprobes-optimization while a kprobe is jump-optimized never returns. The writer sleeps in D state forever with kprobe_sysctl_mutex held, so any later read or write of that sysctl hangs as well. For example, with vfs_read+9 as an optimizable address in this build: # cd /sys/kernel/tracing # echo 'p:myprobe vfs_read+9' >> kprobe_events # echo 1 > events/kprobes/myprobe/enable # # wait until /sys/kernel/debug/kprobes/list shows [OPTIMIZED] # echo 0 > /proc/sys/debug/kprobes-optimization INFO: task sh:246 blocked for more than 10 seconds. Call Trace: <TASK> __schedule+0x1176/0x4f70 schedule+0xdc/0x2c0 schedule_timeout+0x17b/0x260 wait_for_completion+0x173/0x3c0 wait_for_kprobe_optimizer_locked+0xbc/0x130 proc_kprobes_optimization_handler+0x156/0x1b0 proc_sys_call_handler+0x324/0x490 vfs_write+0x52d/0xfe0 ksys_write+0xff/0x200 do_syscall_64+0x106/0x630 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> ... INFO: task cat:265 is blocked on a mutex likely owned by task sh:246. wait_for_kprobe_optimizer_locked() reinitializes optimizer_completion, asks the optimizer thread to flush and sleeps in wait_for_completion(). The thread drains the (un)optimizing lists, but calls complete() only if completion_done() is true, i.e. if the completion is already done, which never happens while someone waits. disarm_all_kprobes() and kprobe_trace_self_tests_init() wait the same way. Calling complete() unconditionally would not be enough: the waiter drops kprobe_mutex while it sleeps, and nothing else serializes the sysctl handler against the debugfs "enabled" file. A second flusher that still finds the lists non-empty, e.g. because a disabled probe is queued for unoptimizing, reinitializes the completion under the first: sysctl write debugfs "enabled" write unoptimize_all_kprobes() wait_for_kprobe_optimizer_locked() init_completion(c) mutex_unlock(&kprobe_mutex) wait_for_completion(c) disarm_all_kprobes() wait_for_kprobe_optimizer_locked() init_completion(c) // c->wait is reset, the first // waiter is off the queue mutex_unlock(&kprobe_mutex) wait_for_completion(c) kprobe_optimizer() complete(c) // wakes the debugfs writer only where c is &optimizer_completion. Lining up the two writes during an optimizer pass loses the sysctl writer this way. Replace the completion with a counter of optimizer passes, bumped at the end of each pass and signalled with wake_up_var_locked(), both under kprobe_mutex. A flusher samples the count and waits with wait_var_event_mutex(), which drops kprobe_mutex only while sleeping, so a new count means a whole pass ran in the meantime. Nothing is reinitialized, so several flushers can sleep in the wait at once.
Impacted products
Vendor Product Version
Linux Linux Version: 73c12f209462d1712c5f55f3021a1b65b2e084c3
Version: 73c12f209462d1712c5f55f3021a1b65b2e084c3
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/kprobes.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f05a01fc7d4f731b4c100d2aef1e85ad77728862",
              "status": "affected",
              "version": "73c12f209462d1712c5f55f3021a1b65b2e084c3",
              "versionType": "git"
            },
            {
              "lessThan": "5bfa9f1a9dcb6ecb607adbc1c0226605c972935b",
              "status": "affected",
              "version": "73c12f209462d1712c5f55f3021a1b65b2e084c3",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/kprobes.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "lessThan": "7.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.9",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkprobes: Fix permanent hang when flushing the kprobe optimizer\n\nWriting 0 to /proc/sys/debug/kprobes-optimization while a kprobe is\njump-optimized never returns. The writer sleeps in D state forever with\nkprobe_sysctl_mutex held, so any later read or write of that sysctl\nhangs as well. For example, with vfs_read+9 as an optimizable address\nin this build:\n\n  # cd /sys/kernel/tracing\n  # echo \u0027p:myprobe vfs_read+9\u0027 \u003e\u003e kprobe_events\n  # echo 1 \u003e events/kprobes/myprobe/enable\n  # # wait until /sys/kernel/debug/kprobes/list shows [OPTIMIZED]\n  # echo 0 \u003e /proc/sys/debug/kprobes-optimization\n\n  INFO: task sh:246 blocked for more than 10 seconds.\n  Call Trace:\n   \u003cTASK\u003e\n   __schedule+0x1176/0x4f70\n   schedule+0xdc/0x2c0\n   schedule_timeout+0x17b/0x260\n   wait_for_completion+0x173/0x3c0\n   wait_for_kprobe_optimizer_locked+0xbc/0x130\n   proc_kprobes_optimization_handler+0x156/0x1b0\n   proc_sys_call_handler+0x324/0x490\n   vfs_write+0x52d/0xfe0\n   ksys_write+0xff/0x200\n   do_syscall_64+0x106/0x630\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n   \u003c/TASK\u003e\n  ...\n  INFO: task cat:265 is blocked on a mutex likely owned by task sh:246.\n\nwait_for_kprobe_optimizer_locked() reinitializes optimizer_completion,\nasks the optimizer thread to flush and sleeps in wait_for_completion().\nThe thread drains the (un)optimizing lists, but calls complete() only\nif completion_done() is true, i.e. if the completion is already done,\nwhich never happens while someone waits. disarm_all_kprobes() and\nkprobe_trace_self_tests_init() wait the same way.\n\nCalling complete() unconditionally would not be enough: the waiter\ndrops kprobe_mutex while it sleeps, and nothing else serializes the\nsysctl handler against the debugfs \"enabled\" file. A second flusher\nthat still finds the lists non-empty, e.g. because a disabled probe is\nqueued for unoptimizing, reinitializes the completion under the first:\n\n  sysctl write                      debugfs \"enabled\" write\n  unoptimize_all_kprobes()\n    wait_for_kprobe_optimizer_locked()\n      init_completion(c)\n      mutex_unlock(\u0026kprobe_mutex)\n      wait_for_completion(c)\n                                    disarm_all_kprobes()\n                                      wait_for_kprobe_optimizer_locked()\n                                        init_completion(c)\n                                          // c-\u003ewait is reset, the first\n                                          // waiter is off the queue\n                                        mutex_unlock(\u0026kprobe_mutex)\n                                        wait_for_completion(c)\n  kprobe_optimizer()\n    complete(c)\n      // wakes the debugfs writer only\n\nwhere c is \u0026optimizer_completion. Lining up the two writes during an\noptimizer pass loses the sysctl writer this way.\n\nReplace the completion with a counter of optimizer passes, bumped at the\nend of each pass and signalled with wake_up_var_locked(), both under\nkprobe_mutex. A flusher samples the count and waits with\nwait_var_event_mutex(), which drops kprobe_mutex only while sleeping, so\na new count means a whole pass ran in the meantime. Nothing is\nreinitialized, so several flushers can sleep in the wait at once."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:21:13.045Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f05a01fc7d4f731b4c100d2aef1e85ad77728862"
        },
        {
          "url": "https://git.kernel.org/stable/c/5bfa9f1a9dcb6ecb607adbc1c0226605c972935b"
        }
      ],
      "title": "kprobes: Fix permanent hang when flushing the kprobe optimizer",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98530",
    "datePublished": "2026-10-18T15:17:48.670Z",
    "dateReserved": "2026-09-25T10:25:14.355Z",
    "dateUpdated": "2026-10-19T09:21:13.045Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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