{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2024-44954",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2024-44954"
  ],
  "published": "2024-09-04T18:36:26Z",
  "summary": "ALSA: line6: Fix racy access to midibuf",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: line6: Fix racy access to midibuf\n\nThere can be concurrent accesses to line6 midibuf from both the URB\ncompletion callback and the rawmidi API access.  This could be a cause\nof KMSAN warning triggered by syzkaller below (so put as reported-by\nhere).\n\nThis patch protects the midibuf call of the former code path with a\nspinlock for avoiding the possible races.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2024-44954"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/643293b68fbb6c03f5e907736498da17d43f0d81"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/40f3d5cb0e0cbf7fa697913a27d5d361373bdcf5"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/e7e7d2b180d8f297cea6db43ea72402fd33e1a29"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a54da4b787dcac60b598da69c9c0072812b8282d"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c80f454a805443c274394b1db0d1ebf477abd94e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/535df7f896a568a8a1564114eaea49d002cb1747"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/51d87f11dd199bbc6a85982b088ff27bde53b48a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/15b7a03205b31bc5623378c190d22b7ff60026f1"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T11:52:36Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The unsynchronized accesses are in `line6_data_received()` (URB completion for the control/MIDI-in endpoint) racing the rawmidi API path, and the driver is only bound when a Line 6 device is already attached \u2014 so a local unprivileged user on such a host drives both halves via `/dev/snd/midiC*D*` (and the hwdep node), writing MIDI/sysex to solicit device replies that generate URB completions while concurrently hammering rawmidi read/trigger. No physical access by the attacker is needed in that deployment (audio workstation, live-performance rig).\nAC:L - The attacker controls both sides of the race \u2014 one thread issues rawmidi/hwdep writes that make the device respond on the interrupt-in endpoint, another thread concurrently exercises the rawmidi API \u2014 and the window can be retried indefinitely at MIDI packet rate. Per the guidance, a race whose both sides the attacker creates is Low.\nPR:L - Only ordinary access to the ALSA rawmidi/hwdep character devices is required, which the console/desktop user gets by default through udev ACLs or `audio` group membership. No CAP_SYS_ADMIN or root is needed.\nUI:N - The attacker performs every step itself \u2014 opening the rawmidi node, soliciting device traffic, and racing the accesses. Presence of the Line 6 device is a property of the affected system (the driver does not load otherwise), not a victim action during the attack.\nS:U - The corrupted ring-buffer state, the heap over-read, and the disclosed data all live in the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - syzbot confirmed \"KMSAN: uninit-value in line6_midibuf_read\" at `midibuf.c:185` \u2014 racy `pos_read`/`pos_write`/`full` make the reader consume bytes never written, so stale contents of the `kmalloc()`ed 1024-byte `midi_buffer.buf` slab object are memcpy'd into `line6->buffer_message` and delivered to userspace through `snd_rawmidi_receive()`. A stale `length1 = size - pos_write`/`pos_read` pair also lets the copy index past the end of that allocation, and the leak is repeatable, allowing kernel heap contents (pointers, recycled data) to be harvested.\nI:H - `line6_midibuf_write()` computes `length1 = this->size - this->pos_write` and then does `memcpy(this->buf + this->pos_write, data, length1)` re-reading `pos_write`; with no lock, a concurrent index update makes that copy run past the end of the kmalloc-1024 object with device-supplied MIDI bytes, giving an attacker-influenced heap out-of-bounds write, and corrupted indices also feed bogus data into the rawmidi stream.\nA:H - Out-of-bounds reads and writes on the kmalloc-1024 slab object corrupt adjacent allocations and trip sanitizer/hardening checks, producing oops or panic. The bug is a memory-safety error, which per the guidance is High availability impact."
    }
  }
}