---
id: CVE-2026-99271
title: 'ALSA: line6: Clear prev_fbuf on capture buffer release'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ALSA: line6: Clear prev_fbuf on capture buffer release

  A KASAN slab-use-after-free read was reported in submit_audio_out_urb()
  when generating an impulse test signal:
  …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 <
    862d9268f40a6e10cef24eb226e738fb69ce8aa7
  - >-
    Linux >= 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 <
    22c82f33ff0b68d37041adf1dea5533a5863cd31
  - >-
    Linux >= 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 <
    aa118c8f61d59387961d58ffae831c5259a9f222
  - Linux 4.0
published: '2026-11-07'
updated: '2026-11-07'
sourceUpdated: '2026-11-07T14:08:45.047Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99271'
references:
  - url: 'https://git.kernel.org/stable/c/862d9268f40a6e10cef24eb226e738fb69ce8aa7'
  - url: 'https://git.kernel.org/stable/c/22c82f33ff0b68d37041adf1dea5533a5863cd31'
  - url: 'https://git.kernel.org/stable/c/aa118c8f61d59387961d58ffae831c5259a9f222'
tags:
  - cve.org
ingestedAt: '2026-11-07T14:18:21.464Z'
---

## Overview

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

ALSA: line6: Clear prev_fbuf on capture buffer release

A KASAN slab-use-after-free read was reported in submit_audio_out_urb()
when generating an impulse test signal:

  BUG: KASAN: slab-use-after-free in create_impulse_test_signal sound/usb/line6/playback.c:76 [inline]
  BUG: KASAN: slab-use-after-free in submit_audio_out_urb+0x1848/0x1b20 sound/usb/line6/playback.c:249
  Read of size 2 at addr ffff888008d74870 by task syz.2.3214/7785

  Allocated by task 11:
   kmem_cache_alloc_noprof+0x2f0/0x390 mm/slub.c:4144
   line6_buffer_acquire+0x1a1/0x220 sound/usb/line6/pcm.c:158
   line6_pcm_acquire+0xb6/0x230 sound/usb/line6/pcm.c:329
   line6_startup_work+0x3c/0x50 sound/usb/line6/driver.c:728

  Freed by task 7785:
   kfree+0xf8/0x390 mm/slub.c:6566
   line6_buffer_release sound/usb/line6/pcm.c:176 [inline]
   line6_buffer_release+0xa5/0xf0 sound/usb/line6/pcm.c:170
   __line6_pcm_release sound/usb/line6/pcm.c:305 [inline]
   line6_pcm_release+0x5a/0x80 sound/usb/line6/pcm.c:313
   snd_toneport_monitor_put+0x11b/0x190 sound/usb/line6/toneport.c:183

line6pcm->prev_fbuf points into the capture PCM stream buffer
(line6pcm->in.buffer), which is updated during audio_in_callback() to
feed rate synchronization, software monitoring, and impulse test signal
generation on playback side.

When all capture streams are closed, line6_buffer_release() frees
pstr->buffer with kfree().  However, it does not clear line6pcm->prev_fbuf.
If playback is subsequently started (e.g. via impulse test signal
volume control snd_line6_impulse_volume_put()), submit_audio_out_urb()
dereferences the stale pointer line6pcm->prev_fbuf under in.lock,
resulting in a slab-use-after-free read.

Clear prev_fbuf and prev_fsize in line6_buffer_release() when releasing
the capture stream buffer under in.lock, ensuring that no stale buffer
pointer can be accessed by submit_audio_out_urb().

## Affected

- `Linux >= 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 < 862d9268f40a6e10cef24eb226e738fb69ce8aa7`
- `Linux >= 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 < 22c82f33ff0b68d37041adf1dea5533a5863cd31`
- `Linux >= 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 < aa118c8f61d59387961d58ffae831c5259a9f222`
- `Linux 4.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.