GHSA-J5V7-FQRF-Q39X

Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31
VLAI
Details

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

ring-buffer: Use current_context for safe per-CPU buffer swap

The ring_buffer_swap_cpu() function currently checks the per-CPU committing counter to determine if a buffer is actively being written to before performing the swap. However, there exists a race window where this check can be bypassed:

ring_buffer_lock_reserve
    cpu_buffer = buffer->buffers[cpu];       // cpu_buffer_a
    rb_reserve_next_event
        rb_start_commit // inc committing
        if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {...}
        __rb_reserve_next
            rb_move_tail
                rb_end_commit(cpu_buffer);   // dec committing => 0
                /* interrupt hits here, successfully swaps! */
                local_inc(&cpu_buffer->committing);

ring_buffer_unlock_commit
    cpu_buffer = buffer->buffers[cpu];      // cpu_buffer_b
    rb_commit
        rb_end_commit
        RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))
                                            // triggers warning

The committing counter can temporarily drop to 0 during a single write operation (within rb_move_tail), creating a window where swap can succeed even though the write is still in progress. This leads to inconsistent buffer state and triggers the RB_WARN_ON in rb_commit().

Replace the committing counter check with current_context checks, which are set at the entry of ring_buffer_lock_reserve() and remain valid throughout the entire write operation, providing a reliable indicator of buffer busy state during swap.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2026-74601"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T16:16:32Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Use current_context for safe per-CPU buffer swap\n\nThe ring_buffer_swap_cpu() function currently checks the per-CPU\ncommitting counter to determine if a buffer is actively being written to\nbefore performing the swap. However, there exists a race window where\nthis check can be bypassed:\n\n    ring_buffer_lock_reserve\n        cpu_buffer = buffer-\u003ebuffers[cpu];       // cpu_buffer_a\n        rb_reserve_next_event\n            rb_start_commit // inc committing\n            if (unlikely(READ_ONCE(cpu_buffer-\u003ebuffer) != buffer)) {...}\n            __rb_reserve_next\n                rb_move_tail\n                    rb_end_commit(cpu_buffer);   // dec committing =\u003e 0\n                    /* interrupt hits here, successfully swaps! */\n                    local_inc(\u0026cpu_buffer-\u003ecommitting);\n\n    ring_buffer_unlock_commit\n        cpu_buffer = buffer-\u003ebuffers[cpu];      // cpu_buffer_b\n        rb_commit\n            rb_end_commit\n            RB_WARN_ON(cpu_buffer, !local_read(\u0026cpu_buffer-\u003ecommitting))\n                                                // triggers warning\n\nThe committing counter can temporarily drop to 0 during a single write\noperation (within rb_move_tail), creating a window where swap can\nsucceed even though the write is still in progress. This leads to\ninconsistent buffer state and triggers the RB_WARN_ON in rb_commit().\n\nReplace the committing counter check with current_context checks, which\nare set at the entry of ring_buffer_lock_reserve() and remain valid\nthroughout the entire write operation, providing a reliable indicator of\nbuffer busy state during swap.",
  "id": "GHSA-j5v7-fqrf-q39x",
  "modified": "2026-08-25T06:31:21Z",
  "published": "2026-08-22T18:30:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74601"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/22709117d9ae95e52673685f98caac7c356a8227"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/26662bc8fced1d668fa1aa146eda085bfc67bd0b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/597f279b7b4a06412e3d965e98cc36e181cdbede"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5b926fb04cb9ef3156dcf88c69a59d3d1a1c4f9f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5e6e2a18c20e88167d414f666032792e8bf19b80"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6b524e6b234e45c7f5f90d13b042c6f57f80105c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ad7e10c7ea89af45ac1bf1814855d45da472703d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f27bdc43077e4fcb5557dfc315ee8d91e741f483"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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