ALSA: oss: Fix PCM OSS buffer allocation overflow

commit efb6402c3c4a7c26d97c92d70186424097b6e366 upstream.

We've got syzbot reports hitting INT_MAX overflow at vmalloc()
allocation that is called from snd_pcm_plug_alloc().  Although we
apply the restrictions to input parameters, it's based only on the
hw_params of the underlying PCM device.  Since the PCM OSS layer
allocates a temporary buffer for the data conversion, the size may
become unexpectedly large when more channels or higher rates is given;
in the reported case, it went over INT_MAX, hence it hits WARN_ON().

This patch is an attempt to avoid such an overflow and an allocation
for too large buffers.  First off, it adds the limit of 1MB as the
upper bound for period bytes.  This must be large enough for all use
cases, and we really don't want to handle a larger temporary buffer
than this size.  The size check is performed at two places, where the
original period bytes is calculated and where the plugin buffer size
is calculated.

In addition, the driver uses array_size() and array3_size() for
multiplications to catch overflows for the converted period size and
buffer bytes.

Reported-by: syzbot+72732c532ac1454eeee9@syzkaller.appspotmail.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/00000000000085b1b305da5a66f3@google.com
Link: https://lore.kernel.org/r/20220318082036.29699-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index cd68a0ae82d311fe341f379ad1d0197e0dd43587..c85fa85285d93e627e784a1b20856b96dc526674 100644 (file)
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -789,6 +789,11 @@ static int snd_pcm_oss_period_size(struct snd_pcm_substream *substream,
 
        if (oss_period_size < 16)
                return -EINVAL;
+
+       /* don't allocate too large period; 1MB period must be enough */
+       if (oss_period_size > 1024 * 1024)
+               return -ENOMEM;
+
        runtime->oss.period_bytes = oss_period_size;
        runtime->oss.period_frames = 1;
        runtime->oss.periods = oss_periods;
@@ -1060,10 +1065,9 @@ static int snd_pcm_oss_change_params_locked(struct snd_pcm_substream *substream)
                        goto failure;
        }
 #endif
-       oss_period_size *= oss_frame_size;
-
-       oss_buffer_size = oss_period_size * runtime->oss.periods;
-       if (oss_buffer_size < 0) {
+       oss_period_size = array_size(oss_period_size, oss_frame_size);
+       oss_buffer_size = array_size(oss_period_size, runtime->oss.periods);
+       if (oss_buffer_size <= 0) {
                err = -EINVAL;
                goto failure;
        }

diff --git a/sound/core/oss/pcm_plugin.c b/sound/core/oss/pcm_plugin.c
index da400da1fafe6758d3bda4e004a980c52756c048..8b7bbabeea24b31bddf6195844b520c9a1f8e1c8 100644 (file)
--- a/sound/core/oss/pcm_plugin.c
+++ b/sound/core/oss/pcm_plugin.c
@@ -61,7 +61,10 @@ static int snd_pcm_plugin_alloc(struct snd_pcm_plugin *plugin, snd_pcm_uframes_t
        }
        if ((width = snd_pcm_format_physical_width(format->format)) < 0)
                return width;
-       size = frames * format->channels * width;
+       size = array3_size(frames, format->channels, width);
+       /* check for too large period size once again */
+       if (size > 1024 * 1024)
+               return -ENOMEM;
        if (snd_BUG_ON(size % 8))
                return -ENXIO;
        size /= 8;