Bug 2568634 (CVE-2026-99271)

Summary:	CVE-2026-99271 kernel: kernel: Denial of service via use-after-free in ALSA Line 6 audio driver
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Advanced Linux Sound Architecture (ALSA) Line 6 USB audio driver. When releasing audio capture buffers, the driver fails to clear an internal buffer pointer, leaving a stale reference to freed memory. A local user can exploit this issue by triggering audio playback after closing a capture stream, resulting in a use-after-free condition that may lead to a denial of service (system crash) or unauthorized memory disclosure.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-11-07 14:22:21 UTC

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().