GHSA-F958-2RWJ-98RC

Vulnerability from github – Published: 2026-10-06 09:31 – Updated: 2026-10-06 09:31
VLAI
Details

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

ALSA: pcm: set timer->private_data before registering the PCM timer

snd_pcm_timer_init() calls snd_device_register() to link the new struct snd_timer into the global timer list while it still carries hw.c_resolution = snd_pcm_timer_resolution (and hw.start/hw.stop), and only afterwards sets timer->private_data = substream.

Once the timer is on the list under register_mutex, a concurrent reader can already reach it through the same mutex and invoke these callbacks. /proc/asound/timers does this via c_resolution(), and snd_timer_open()+snd_timer_start() reach start()/stop() the same way. All three dereference timer->private_data, which for this brief window is NULL, giving a NULL-pointer dereference:

substream = timer->private_data; return substream->runtime ? ... // substream is NULL

Move the private_data/private_free assignment before snd_device_register() so the timer is never visible on the list without its private_data set. On the snd_device_register() failure path, private_free() (snd_pcm_timer_free()) can now run, but it only does substream->timer = NULL, which is already NULL at that point since substream->timer is set to the new timer just once, after a successful registration -- so the failure path stays safe.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98314"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-06T09:18:23Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: set timer-\u003eprivate_data before registering the PCM timer\n\nsnd_pcm_timer_init() calls snd_device_register() to link the new\nstruct snd_timer into the global timer list while it still carries\nhw.c_resolution = snd_pcm_timer_resolution (and hw.start/hw.stop),\nand only afterwards sets timer-\u003eprivate_data = substream.\n\nOnce the timer is on the list under register_mutex, a concurrent\nreader can already reach it through the same mutex and invoke these\ncallbacks. /proc/asound/timers does this via c_resolution(), and\nsnd_timer_open()+snd_timer_start() reach start()/stop() the same way.\nAll three dereference timer-\u003eprivate_data, which for this brief\nwindow is NULL, giving a NULL-pointer dereference:\n\n  substream = timer-\u003eprivate_data;\n  return substream-\u003eruntime ? ...   // substream is NULL\n\nMove the private_data/private_free assignment before\nsnd_device_register() so the timer is never visible on the list\nwithout its private_data set. On the snd_device_register() failure\npath, private_free() (snd_pcm_timer_free()) can now run, but it only\ndoes substream-\u003etimer = NULL, which is already NULL at that point\nsince substream-\u003etimer is set to the new timer just once, after a\nsuccessful registration -- so the failure path stays safe.",
  "id": "GHSA-f958-2rwj-98rc",
  "modified": "2026-10-06T09:31:34Z",
  "published": "2026-10-06T09:31:34Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98314"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0b349249d572633d7c8cdeb917623d1676a2b7c3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1e713f9bb2ac583521f06b0eb4e22440b1e3d078"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/27f167e117eca310661fbcbacb352ea08face067"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/555d168bd98daa46daccc68c908201388c834293"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/686c7a6af1eea8d2a919303e4c6bbec3de79dbdc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8c869d5cf5affb20994bdbb60e7d46d65c91b55f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d63f5a9f8121fb43c798056d7dd34c58f47185d7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e1eee8f16628f8b6bcae0a366fd6a2dd65e71edd"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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