Vulnerability-Lookup

GHSA-XVP7-XR44-89MJ

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-25 12:31

Details

In the Linux kernel, the following vulnerability has been resolved:

tracing: Fix NULL pointer dereference in func_set_flag()

func_set_flag() dereferences tr->current_trace_flags before verifying that the current tracer is actually the function tracer. When the active tracer has been switched away from "function" (e.g., to "wakeup_rt"), tr->current_trace_flags can be NULL, leading to a NULL pointer dereference and kernel crash.

The call chain that triggers this is:

trace_options_write() -> __set_tracer_option() -> trace->set_flag() / func_set_flag /

In func_set_flag(), the first operation is:

if (!!set == !!(tr->current_trace_flags->val & bit))

This dereferences tr->current_trace_flags unconditionally. The safety check that guards against a non-function tracer:

if (tr->current_trace != &function_trace) return 0;

is placed after the dereference, which is too late.

This was observed with the following crash dump:

BUG: unable to handle page fault at 0000000000000000 RIP: func_set_flag+0xd

Call Trace: __set_tracer_option+0x27 trace_options_write+0x75 vfs_write+0x12a ksys_write+0x66 do_syscall_64+0x5b

RIP: ffffffff914c973d RSP: ff67ec88b01dfdf0 RFLAGS: 00010202 RAX: 0000000000000000 RBX: ff3a826e80354580 RCX: 0000000000000001 RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffff93918080

The disassembly confirms the fault:

func_set_flag+0: mov 0x1f08(%rdi), %rax ; RAX = tr->current_trace_flags = NULL func_set_flag+13: mov (%rax), %eax ; page fault: dereference NULL

At the time of the crash: tr->current_trace_flags = 0x0 (NULL) tr->current_trace = wakeup_rt_tracer (not function_trace)

The scenario is that a process opens a function tracer option file (such as "func_stack_trace"), then the current tracer is switched to another tracer (e.g., "wakeup_rt"), which sets current_trace_flags to NULL. When the process subsequently writes to the option file, func_set_flag() is invoked and crashes on the NULL dereference.

Fix this by moving the current_trace check before the current_trace_flags dereference, so that func_set_flag() returns early when the function tracer is not active.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-64451"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:30Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix NULL pointer dereference in func_set_flag()\n\nfunc_set_flag() dereferences tr-\u003ecurrent_trace_flags before verifying\nthat the current tracer is actually the function tracer. When the active\ntracer has been switched away from \"function\" (e.g., to \"wakeup_rt\"),\ntr-\u003ecurrent_trace_flags can be NULL, leading to a NULL pointer\ndereference and kernel crash.\n\nThe call chain that triggers this is:\n\n  trace_options_write()\n    -\u003e __set_tracer_option()\n      -\u003e trace-\u003eset_flag()          /* func_set_flag */\n\nIn func_set_flag(), the first operation is:\n\n  if (!!set == !!(tr-\u003ecurrent_trace_flags-\u003eval \u0026 bit))\n\nThis dereferences tr-\u003ecurrent_trace_flags unconditionally. The safety\ncheck that guards against a non-function tracer:\n\n  if (tr-\u003ecurrent_trace != \u0026function_trace)\n      return 0;\n\nis placed *after* the dereference, which is too late.\n\nThis was observed with the following crash dump:\n\n  BUG: unable to handle page fault at 0000000000000000\n  RIP: func_set_flag+0xd\n\n  Call Trace:\n   __set_tracer_option+0x27\n   trace_options_write+0x75\n   vfs_write+0x12a\n   ksys_write+0x66\n   do_syscall_64+0x5b\n\n  RIP: ffffffff914c973d  RSP: ff67ec88b01dfdf0  RFLAGS: 00010202\n  RAX: 0000000000000000  RBX: ff3a826e80354580  RCX: 0000000000000001\n  RDX: 0000000000000001  RSI: 0000000000000000  RDI: ffffffff93918080\n\nThe disassembly confirms the fault:\n\n  func_set_flag+0:   mov 0x1f08(%rdi), %rax  ; RAX = tr-\u003ecurrent_trace_flags = NULL\n  func_set_flag+13:  mov (%rax), %eax        ; page fault: dereference NULL\n\nAt the time of the crash:\n  tr-\u003ecurrent_trace_flags = 0x0 (NULL)\n  tr-\u003ecurrent_trace = wakeup_rt_tracer (not function_trace)\n\nThe scenario is that a process opens a function tracer option file (such\nas \"func_stack_trace\"), then the current tracer is switched to another\ntracer (e.g., \"wakeup_rt\"), which sets current_trace_flags to NULL. When\nthe process subsequently writes to the option file, func_set_flag() is\ninvoked and crashes on the NULL dereference.\n\nFix this by moving the current_trace check before the\ncurrent_trace_flags dereference, so that func_set_flag() returns early\nwhen the function tracer is not active.",
  "id": "GHSA-xvp7-xr44-89mj",
  "modified": "2026-07-25T12:31:36Z",
  "published": "2026-07-25T12:31:36Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64451"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/69f17ac132a38974cf1defb480cef6b79d1ab768"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c3e94604675e3db186111b8942650d86577df9b0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-64451 (GCVE-0-2026-64451)

Vulnerability from cvelistv5 – Published: 2026-07-25 08:51 – Updated: 2026-07-25 08:51

Title

tracing: Fix NULL pointer dereference in func_set_flag()

Summary

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix NULL pointer dereference in func_set_flag() func_set_flag() dereferences tr->current_trace_flags before verifying that the current tracer is actually the function tracer. When the active tracer has been switched away from "function" (e.g., to "wakeup_rt"), tr->current_trace_flags can be NULL, leading to a NULL pointer dereference and kernel crash. The call chain that triggers this is: trace_options_write() -> __set_tracer_option() -> trace->set_flag() /* func_set_flag */ In func_set_flag(), the first operation is: if (!!set == !!(tr->current_trace_flags->val & bit)) This dereferences tr->current_trace_flags unconditionally. The safety check that guards against a non-function tracer: if (tr->current_trace != &function_trace) return 0; is placed *after* the dereference, which is too late. This was observed with the following crash dump: BUG: unable to handle page fault at 0000000000000000 RIP: func_set_flag+0xd Call Trace: __set_tracer_option+0x27 trace_options_write+0x75 vfs_write+0x12a ksys_write+0x66 do_syscall_64+0x5b RIP: ffffffff914c973d RSP: ff67ec88b01dfdf0 RFLAGS: 00010202 RAX: 0000000000000000 RBX: ff3a826e80354580 RCX: 0000000000000001 RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffff93918080 The disassembly confirms the fault: func_set_flag+0: mov 0x1f08(%rdi), %rax ; RAX = tr->current_trace_flags = NULL func_set_flag+13: mov (%rax), %eax ; page fault: dereference NULL At the time of the crash: tr->current_trace_flags = 0x0 (NULL) tr->current_trace = wakeup_rt_tracer (not function_trace) The scenario is that a process opens a function tracer option file (such as "func_stack_trace"), then the current tracer is switched to another tracer (e.g., "wakeup_rt"), which sets current_trace_flags to NULL. When the process subsequently writes to the option file, func_set_flag() is invoked and crashes on the NULL dereference. Fix this by moving the current_trace check before the current_trace_flags dereference, so that func_set_flag() returns early when the function tracer is not active.

Severity

No CVSS data available.

Assigner

Linux

References

2 references

URL	Tags
https://git.kernel.org/stable/c/69f17ac132a38974c…
https://git.kernel.org/stable/c/c3e94604675e3db18…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 76680d0d2825900f23bf35290ab2b80bdf3a8e4a , < 69f17ac132a38974cf1defb480cef6b79d1ab768 (git) Affected: 76680d0d2825900f23bf35290ab2b80bdf3a8e4a , < c3e94604675e3db186111b8942650d86577df9b0 (git)
Linux	Linux	Affected: 6.19 Unaffected: 0 , < 6.19 (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc3 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace_functions.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "69f17ac132a38974cf1defb480cef6b79d1ab768",
              "status": "affected",
              "version": "76680d0d2825900f23bf35290ab2b80bdf3a8e4a",
              "versionType": "git"
            },
            {
              "lessThan": "c3e94604675e3db186111b8942650d86577df9b0",
              "status": "affected",
              "version": "76680d0d2825900f23bf35290ab2b80bdf3a8e4a",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace_functions.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.4",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2-rc3",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix NULL pointer dereference in func_set_flag()\n\nfunc_set_flag() dereferences tr-\u003ecurrent_trace_flags before verifying\nthat the current tracer is actually the function tracer. When the active\ntracer has been switched away from \"function\" (e.g., to \"wakeup_rt\"),\ntr-\u003ecurrent_trace_flags can be NULL, leading to a NULL pointer\ndereference and kernel crash.\n\nThe call chain that triggers this is:\n\n  trace_options_write()\n    -\u003e __set_tracer_option()\n      -\u003e trace-\u003eset_flag()          /* func_set_flag */\n\nIn func_set_flag(), the first operation is:\n\n  if (!!set == !!(tr-\u003ecurrent_trace_flags-\u003eval \u0026 bit))\n\nThis dereferences tr-\u003ecurrent_trace_flags unconditionally. The safety\ncheck that guards against a non-function tracer:\n\n  if (tr-\u003ecurrent_trace != \u0026function_trace)\n      return 0;\n\nis placed *after* the dereference, which is too late.\n\nThis was observed with the following crash dump:\n\n  BUG: unable to handle page fault at 0000000000000000\n  RIP: func_set_flag+0xd\n\n  Call Trace:\n   __set_tracer_option+0x27\n   trace_options_write+0x75\n   vfs_write+0x12a\n   ksys_write+0x66\n   do_syscall_64+0x5b\n\n  RIP: ffffffff914c973d  RSP: ff67ec88b01dfdf0  RFLAGS: 00010202\n  RAX: 0000000000000000  RBX: ff3a826e80354580  RCX: 0000000000000001\n  RDX: 0000000000000001  RSI: 0000000000000000  RDI: ffffffff93918080\n\nThe disassembly confirms the fault:\n\n  func_set_flag+0:   mov 0x1f08(%rdi), %rax  ; RAX = tr-\u003ecurrent_trace_flags = NULL\n  func_set_flag+13:  mov (%rax), %eax        ; page fault: dereference NULL\n\nAt the time of the crash:\n  tr-\u003ecurrent_trace_flags = 0x0 (NULL)\n  tr-\u003ecurrent_trace = wakeup_rt_tracer (not function_trace)\n\nThe scenario is that a process opens a function tracer option file (such\nas \"func_stack_trace\"), then the current tracer is switched to another\ntracer (e.g., \"wakeup_rt\"), which sets current_trace_flags to NULL. When\nthe process subsequently writes to the option file, func_set_flag() is\ninvoked and crashes on the NULL dereference.\n\nFix this by moving the current_trace check before the\ncurrent_trace_flags dereference, so that func_set_flag() returns early\nwhen the function tracer is not active."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-25T08:51:21.020Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/69f17ac132a38974cf1defb480cef6b79d1ab768"
        },
        {
          "url": "https://git.kernel.org/stable/c/c3e94604675e3db186111b8942650d86577df9b0"
        }
      ],
      "title": "tracing: Fix NULL pointer dereference in func_set_flag()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64451",
    "datePublished": "2026-07-25T08:51:21.020Z",
    "dateReserved": "2026-07-19T15:36:31.788Z",
    "dateUpdated": "2026-07-25T08:51:21.020Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

GHSA-XVP7-XR44-89MJ

CVE-2026-64451 (GCVE-0-2026-64451)

Tags

Sightings

Nomenclature