CVE-2026-89771 (GCVE-0-2026-89771)
Vulnerability from cvelistv5
Published
2026-09-11 19:47
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: ring-buffer: Fix subbuf resize race with ring buffer readers trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and ring_buffer_read_start(), while it can simultaneously be resized with ring_buffer_subbuf_order_set(). Instead of trace_buffer::subbuf_size, use bpage::order in ring_buffer_read_start() and ring_buffer_read_page(). In ring_buffer_read_start(), even with resize_disabled, there is still a possibility of a race with a buffer modification. Hold the trace_buffer mutex to synchronise with any pending ring buffer order modification. trace_buffer::subbuf_size is now actually useless, remove it. Also, create accessors rb_subbuf_capacity() and rb_page_capacity() which return the actual size available for storing events, while rb_subbuf_size() returns the actual subbuf page-size.
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/ring_buffer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/trace/ring_buffer.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
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              "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": [
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          "nodes": [
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              "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
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                {
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                  "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\nring-buffer: Fix subbuf resize race with ring buffer readers\n\ntrace_buffer subbuf_size is read lockless in ring_buffer_read_page() and\nring_buffer_read_start(), while it can simultaneously be resized with\nring_buffer_subbuf_order_set().\n\nInstead of trace_buffer::subbuf_size, use bpage::order in\nring_buffer_read_start() and ring_buffer_read_page().\n\nIn ring_buffer_read_start(), even with resize_disabled, there is still a\npossibility of a race with a buffer modification. Hold the trace_buffer\nmutex to synchronise with any pending ring buffer order modification.\n\ntrace_buffer::subbuf_size is now actually useless, remove it. Also,\ncreate accessors rb_subbuf_capacity() and rb_page_capacity() which\nreturn the actual size available for storing events, while\nrb_subbuf_size() returns the actual subbuf page-size."
        }
      ],
      "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 bug is reached only via local tracefs: write() to buffer_subbuf_size_kb (ring_buffer_subbuf_order_set) racing with read()/splice() of per_cpu/*/trace_pipe_raw (ring_buffer_read_page) or open/read of trace (ring_buffer_read_start). No network, adjacent-radio, or physical path exists.\nAC:L - The attacker controls both sides: one thread writes buffer_subbuf_size_kb while another reads trace_pipe_raw or trace. ring_buffer_subbuf_order_set publishes the new subbuf_size before allocating replacement pages and without reader_lock, so the window includes synchronize_rcu() plus GFP_KERNEL allocation and is reliably retried.\nPR:L - tracing_check_open_get_tr() enforces only LOCKDOWN_TRACEFS and DAC with no capable() check. buffer_subbuf_size_kb is 0640 and trace_pipe_raw/trace are 0440/0640, routinely delegated via tracefs gid=/mode= to tracing-group members on Android/Perfetto, ChromeOS, and developer systems, matching CVE-2024-50207 and CVE-2026-74634.\nUI:N - Exploitation uses the attacker\u0027s own tracefs file descriptors and threads (write buffer_subbuf_size_kb while reading trace_pipe_raw or trace). No separate victim mount, click, or configuration action is required.\nS:U - The out-of-bounds memset/memcpy corrupt kernel ring-buffer pages and adjacent heap within the same OS security authority. This enables local privilege escalation but does not cross VM, IOMMU, container, or hardware trust boundaries.\nC:H - ring_buffer_read_page() uses the lockless new subbuf_size to memset/memcpy past an old-order spare or reader page, and tracing_buffers_read copy_to_user of that oversized length discloses adjacent kernel heap to userspace. The same OOB corruption is also a high-impact read primitive.\nI:H - After a passing order check, ring_buffer_read_page() memset()s (new_subbuf_size-size) bytes past the still-old data page (up to hundreds of KB when order jumps 0 to 7). That kernel heap OOB write is exploitable for arbitrary writes and control-flow hijack, not merely a crash.\nA:H - The same OOB memset/memcpy corrupt adjacent kernel objects and ring-buffer metadata, producing oops/panic. The attacker chooses the order delta via buffer_subbuf_size_kb and can retrigger the race at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:24.715Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9"
        },
        {
          "url": "https://git.kernel.org/stable/c/50f4a793c4ff24826efb0ac700989a5063cc53df"
        },
        {
          "url": "https://git.kernel.org/stable/c/0c7c517827a453128a8f58bfd849546a29813b27"
        },
        {
          "url": "https://git.kernel.org/stable/c/8a5f63637890f03177146efddaba5ec7a1b4d61f"
        }
      ],
      "title": "ring-buffer: Fix subbuf resize race with ring buffer readers",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89771",
    "datePublished": "2026-09-11T19:47:10.381Z",
    "dateReserved": "2026-09-11T19:38:34.765Z",
    "dateUpdated": "2026-10-19T08:52:24.715Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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