From: Takashi Iwai <tiwai@suse.de>
To: alsa-devel@alsa-project.org
Subject: [PATCH] ALSA: pcm: oss: Avoid plugin buffer overflow
Date: Mon, 9 Mar 2020 09:21:48 +0100 [thread overview]
Message-ID: <20200309082148.19855-1-tiwai@suse.de> (raw)
Each OSS PCM plugins allocate its internal buffer per pre-calculation
of the max buffer size through the chain of plugins (calling
src_frames and dst_frames callbacks). This works for most plugins,
but the rate plugin might behave incorrectly. The calculation in the
rate plugin involves with the fractional position, i.e. it may vary
depending on the input position. Since the buffer size
pre-calculation is always done with the offset zero, it may return a
shorter size than it might be; this may result in the out-of-bound
access as spotted by fuzzer.
This patch addresses those possible buffer overflow accesses by simply
setting the upper limit per the given buffer size for each plugin
before src_frames() and after dst_frames() calls.
Reported-by: syzbot+e1fe9f44fb8ecf4fb5dd@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/000000000000b25ea005a02bcf21@google.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/core/oss/pcm_plugin.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/sound/core/oss/pcm_plugin.c b/sound/core/oss/pcm_plugin.c
index 240e4702c098..c9401832967c 100644
--- a/sound/core/oss/pcm_plugin.c
+++ b/sound/core/oss/pcm_plugin.c
@@ -209,6 +209,8 @@ snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *plug, snd_p
if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
plugin = snd_pcm_plug_last(plug);
while (plugin && drv_frames > 0) {
+ if (drv_frames > plugin->buf_frames)
+ drv_frames = plugin->buf_frames;
plugin_prev = plugin->prev;
if (plugin->src_frames)
drv_frames = plugin->src_frames(plugin, drv_frames);
@@ -220,6 +222,8 @@ snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *plug, snd_p
plugin_next = plugin->next;
if (plugin->dst_frames)
drv_frames = plugin->dst_frames(plugin, drv_frames);
+ if (drv_frames > plugin->buf_frames)
+ drv_frames = plugin->buf_frames;
plugin = plugin_next;
}
} else
@@ -248,11 +252,15 @@ snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *plug, snd_pc
if (frames < 0)
return frames;
}
+ if (frames > plugin->buf_frames)
+ frames = plugin->buf_frames;
plugin = plugin_next;
}
} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
plugin = snd_pcm_plug_last(plug);
while (plugin) {
+ if (frames > plugin->buf_frames)
+ frames = plugin->buf_frames;
plugin_prev = plugin->prev;
if (plugin->src_frames) {
frames = plugin->src_frames(plugin, frames);
--
2.16.4
next reply other threads:[~2020-03-09 8:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 8:21 Takashi Iwai [this message]
2020-04-30 16:34 ` [PATCH] ALSA: pcm: oss: Avoid plugin buffer overflow Serge Belyshev
2020-04-30 16:44 ` Takashi Iwai
2020-04-30 17:35 ` Serge Belyshev
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