From d2d135cba85ba02da07f43b1f1d7d9fb3937a8f2 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 4 Dec 2019 15:48:24 +0100 Subject: [PATCH] ALSA: pcm: oss: Avoid potential buffer overflows commit 4cc8d6505ab82db3357613d36e6c58a297f57f7c upstream. syzkaller reported an invalid access in PCM OSS read, and this seems to be an overflow of the internal buffer allocated for a plugin. Since the rate plugin adjusts its transfer size dynamically, the calculation for the chained plugin might be bigger than the given buffer size in some extreme cases, which lead to such an buffer overflow as caught by KASAN. Fix it by limiting the max transfer size properly by checking against the destination size in each plugin transfer callback. Reported-by: syzbot+f153bde47a62e0b05f83@syzkaller.appspotmail.com Cc: Link: https://lore.kernel.org/r/20191204144824.17801-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/oss/linear.c | 2 ++ sound/core/oss/mulaw.c | 2 ++ sound/core/oss/route.c | 2 ++ 3 files changed, 6 insertions(+) diff --git a/sound/core/oss/linear.c b/sound/core/oss/linear.c index 2045697..797d838 100644 --- a/sound/core/oss/linear.c +++ b/sound/core/oss/linear.c @@ -107,6 +107,8 @@ static snd_pcm_sframes_t linear_transfer(struct snd_pcm_plugin *plugin, } } #endif + if (frames > dst_channels[0].frames) + frames = dst_channels[0].frames; convert(plugin, src_channels, dst_channels, frames); return frames; } diff --git a/sound/core/oss/mulaw.c b/sound/core/oss/mulaw.c index 7915564..3788906 100644 --- a/sound/core/oss/mulaw.c +++ b/sound/core/oss/mulaw.c @@ -269,6 +269,8 @@ static snd_pcm_sframes_t mulaw_transfer(struct snd_pcm_plugin *plugin, } } #endif + if (frames > dst_channels[0].frames) + frames = dst_channels[0].frames; data = (struct mulaw_priv *)plugin->extra_data; data->func(plugin, src_channels, dst_channels, frames); return frames; diff --git a/sound/core/oss/route.c b/sound/core/oss/route.c index c8171f5..72dea04 100644 --- a/sound/core/oss/route.c +++ b/sound/core/oss/route.c @@ -57,6 +57,8 @@ static snd_pcm_sframes_t route_transfer(struct snd_pcm_plugin *plugin, return -ENXIO; if (frames == 0) return 0; + if (frames > dst_channels[0].frames) + frames = dst_channels[0].frames; nsrcs = plugin->src_format.channels; ndsts = plugin->dst_format.channels; -- 2.7.4