From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-99271: ALSA: line6: Clear prev_fbuf on capture buffer release
Date: Sat, 7 Nov 2026 09:08:51 -0500 [thread overview]
Message-ID: <2026110751-CVE-2026-99271-e93e@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
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().
The Linux kernel CVE team has assigned CVE-2026-99271 to this issue.
Affected and fixed versions
===========================
Issue introduced in 4.0 with commit 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 and fixed in 6.18.61 with commit 862d9268f40a6e10cef24eb226e738fb69ce8aa7
Issue introduced in 4.0 with commit 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 and fixed in 7.3.2 with commit 22c82f33ff0b68d37041adf1dea5533a5863cd31
Issue introduced in 4.0 with commit 63e20df1e5b2ef8d871ecbdb6c038d554ed1ca74 and fixed in 7.4-rc1 with commit aa118c8f61d59387961d58ffae831c5259a9f222
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-99271
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
sound/usb/line6/pcm.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/862d9268f40a6e10cef24eb226e738fb69ce8aa7
https://git.kernel.org/stable/c/22c82f33ff0b68d37041adf1dea5533a5863cd31
https://git.kernel.org/stable/c/aa118c8f61d59387961d58ffae831c5259a9f222
reply other threads:[~2026-11-07 15:33 UTC|newest]
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