From: Takashi Iwai <tiwai@suse.de>
To: Yuanzhe Liu <25031212351@stu.xidian.edu.cn>
Cc: Takashi Iwai <tiwai@suse.com>, Jaroslav Kysela <perex@perex.cz>,
linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, Bin Yu <byu@xidian.edu.cn>,
Cheng Wen <wencheng@xidian.edu.cn>
Subject: Re: [PATCH] ALSA: line6: Clear prev_fbuf on capture buffer release
Date: Tue, 13 Oct 2026 09:08:52 +0200 [thread overview]
Message-ID: <87bj8yoz5n.wl-tiwai@suse.de> (raw)
In-Reply-To: <20261013063554.571-1-25031212351@stu.xidian.edu.cn>
On Tue, 13 Oct 2026 08:35:54 +0200,
Yuanzhe Liu wrote:
>
> From: YuanZhe Liu <25031212351@stu.xidian.edu.cn>
>
> 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().
>
> Fixes: 63e20df1e5b2 ("ALSA: line6: Reorganize PCM stream handling")
> Cc: stable@vger.kernel.org
> Co-developed-by: Bin Yu <byu@xidian.edu.cn>
> Signed-off-by: Bin Yu <byu@xidian.edu.cn>
> Co-developed-by: Cheng Wen <wencheng@xidian.edu.cn>
> Signed-off-by: Cheng Wen <wencheng@xidian.edu.cn>
> Signed-off-by: YuanZhe Liu <25031212351@stu.xidian.edu.cn>
Applied to for-next branch. Thanks.
Takashi
prev parent reply other threads:[~2026-10-13 7:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-13 6:35 [PATCH] ALSA: line6: Clear prev_fbuf on capture buffer release Yuanzhe Liu
2026-10-13 7:08 ` Takashi Iwai [this message]
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