CVE-2026-89747 (GCVE-0-2026-89747)
Vulnerability from cvelistv5
Published
2026-09-11 19:46
Modified
2026-10-19 08:52
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event.
References
Impacted products
Vendor Product Version
Linux Linux Version: f9b94daa542a8d2532f0930f01cd9aec2d19621b
Version: f9b94daa542a8d2532f0930f01cd9aec2d19621b
Version: f9b94daa542a8d2532f0930f01cd9aec2d19621b
Version: f9b94daa542a8d2532f0930f01cd9aec2d19621b
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "05ebe1e1d7d38c2612bacfefe043a33572ae34cb",
              "status": "affected",
              "version": "f9b94daa542a8d2532f0930f01cd9aec2d19621b",
              "versionType": "git"
            },
            {
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              "versionType": "git"
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              "lessThan": "372f8534244d632ad5118e8a87a11291b01712d3",
              "status": "affected",
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              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/trace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "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": "6.12.109",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.50",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.4",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix use-after-free in trace_pipe read on sub-buffer order change\n\nWriting to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(),\nwhich frees every sub-buffer of the ring buffer, including the reader\npage, and replaces them with newly allocated ones.\n\nReaders of trace_pipe hold pointers into those pages. ring_buffer_peek()\nlooks up an event under cpu_buffer-\u003ereader_lock but returns the event\npointer after dropping the lock, and peek_next_entry() then calls\nring_buffer_event_length() and ring_buffer_event_data() on it. If the\nsub-buffer order is changed in that window, the reader dereferences\nfreed memory:\n\n  BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430\n  Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002\n\n  Freed by:\n   free_buffer_page kernel/trace/ring_buffer.c:398 [inline]\n   ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444\n   buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221\n\nTake trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change.\nThis is the lock trace_pipe readers already hold across their entire\npeek-and-print loop, so the swap can no longer race with a reader that\nis dereferencing a peeked event."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is reached only via local tracefs: write() to buffer_subbuf_size_kb (buffer_subbuf_size_write -\u003e ring_buffer_subbuf_order_set) racing with read()/splice() of trace_pipe (tracing_read_pipe -\u003e ring_buffer_peek). No network, adjacent-radio, or physical-device path reaches this code.\nAC:L - The attacker controls both sides of the race: one thread reads trace_pipe while another writes buffer_subbuf_size_kb, which frees the reader page after dropping reader_lock. ring_buffer_peek then dereferences the stale event pointer; the attempt is retryable at will and CONFIG_TRACING is standard.\nPR:L - tracing_check_open_get_tr() checks only LOCKDOWN_TRACEFS and DAC, with no capable() gate. buffer_subbuf_size_kb (0640) and trace_pipe (0440) are delegated via uid=/gid= mounts to tracing-group accounts on Android/Perfetto, ChromeOS, and developer systems, matching CVE-2025-38101 and CVE-2026-74634.\nUI:N - The attacker opens and reads their own trace_pipe and writes buffer_subbuf_size_kb from their own threads. No victim action, mount, or file open by another user is required.\nS:U - The use-after-free corrupts kernel ring-buffer pages and metadata inside the host kernel\u0027s security authority. It can yield local privilege escalation but does not cross a VM, IOMMU, container, or hardware trust boundary.\nC:H - ring_buffer_subbuf_order_set() frees reader-page sub-buffers while ring_buffer_peek() still holds a pointer into them; peek_next_entry() and print_trace_line() then read the freed event and copy it to userspace via trace_pipe, disclosing recycled kernel heap contents.\nI:H - Freed sub-buffer pages and buffer_page objects can be reallocated while the reader still consumes attacker-controlled type_len/payload and print_trace_line() dispatches on iter-\u003eent-\u003etype. This UAF heap corruption is exploitable for arbitrary kernel writes and control-flow hijack.\nA:H - Dereferencing the freed reader page in ring_buffer_peek()/ring_buffer_event_length() causes a kernel oops, which is the syzbot KASAN use-after-free. The attacker can retrigger that crash at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:01.177Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/05ebe1e1d7d38c2612bacfefe043a33572ae34cb"
        },
        {
          "url": "https://git.kernel.org/stable/c/ddbe921ed16a0ad2d9e09574c3f3aabec7528325"
        },
        {
          "url": "https://git.kernel.org/stable/c/7a49d19ff9baaf61217e5ec14199c18bc2d93ee4"
        },
        {
          "url": "https://git.kernel.org/stable/c/372f8534244d632ad5118e8a87a11291b01712d3"
        }
      ],
      "title": "tracing: Fix use-after-free in trace_pipe read on sub-buffer order change",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89747",
    "datePublished": "2026-09-11T19:46:52.268Z",
    "dateReserved": "2026-09-11T19:38:34.762Z",
    "dateUpdated": "2026-10-19T08:52:01.177Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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