[PATCH 5.10 048/132] ALSA: pcm: oss: Fix negative period/buffer sizes

Greg Kroah-Hartman
2021-12-13T10:08:07Z

From: Takashi Iwai <tiwai@suse.de>

commit 9d2479c960875ca1239bcb899f386970c13d9cfe upstream.

The period size calculation in OSS layer may receive a negative value
as an error, but the code there assumes only the positive values and
handle them with size_t. Due to that, a too big value may be passed
to the lower layers.

This patch changes the code to handle with ssize_t and adds the proper
error checks appropriately.

Reported-by: syzbot+bb348e9f9a954d42746f@syzkaller.appspotmail.com
Reported-by: Bixuan Cui <cuibixuan@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1638270978-42412-1-git-send-email-cuibixuan@linux.alibaba.com
Link: https://lore.kernel.org/r/20211201073606.11660-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/core/oss/pcm_oss.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -147,7 +147,7 @@ snd_pcm_hw_param_value_min(const struct
*
* Return the maximum value for field PAR.
*/
-static unsigned int
+static int
snd_pcm_hw_param_value_max(const struct snd_pcm_hw_params *params,
snd_pcm_hw_param_t var, int *dir)
{
@@ -682,18 +682,24 @@ static int snd_pcm_oss_period_size(struc
struct snd_pcm_hw_params *oss_params,
struct snd_pcm_hw_params *slave_params)
{
- size_t s;
- size_t oss_buffer_size, oss_period_size, oss_periods;
- size_t min_period_size, max_period_size;
+ ssize_t s;
+ ssize_t oss_buffer_size;
+ ssize_t oss_period_size, oss_periods;
+ ssize_t min_period_size, max_period_size;
struct snd_pcm_runtime *runtime = substream->runtime;
size_t oss_frame_size;

oss_frame_size = snd_pcm_format_physical_width(params_format(oss_params)) *
params_channels(oss_params) / 8;

+ oss_buffer_size = snd_pcm_hw_param_value_max(slave_params,
+ SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
+ NULL);
+ if (oss_buffer_size <= 0)
+ return -EINVAL;
oss_buffer_size = snd_pcm_plug_client_size(substream,
- snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_BUFFER_SIZE, NULL)) * oss_frame_size;
- if (!oss_buffer_size)
+ oss_buffer_size * oss_frame_size);
+ if (oss_buffer_size <= 0)
return -EINVAL;
oss_buffer_size = rounddown_pow_of_two(oss_buffer_size);
if (atomic_read(&substream->mmap_count)) {
@@ -730,7 +736,7 @@ static int snd_pcm_oss_period_size(struc

min_period_size = snd_pcm_plug_client_size(substream,
snd_pcm_hw_param_value_min(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
- if (min_period_size) {
+ if (min_period_size > 0) {
min_period_size *= oss_frame_size;
min_period_size = roundup_pow_of_two(min_period_size);
if (oss_period_size < min_period_size)
@@ -739,7 +745,7 @@ static int snd_pcm_oss_period_size(struc

max_period_size = snd_pcm_plug_client_size(substream,
snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, NULL));
- if (max_period_size) {
+ if (max_period_size > 0) {
max_period_size *= oss_frame_size;
max_period_size = rounddown_pow_of_two(max_period_size);
if (oss_period_size > max_period_size)
@@ -752,7 +758,7 @@ static int snd_pcm_oss_period_size(struc
oss_periods = substream->oss.setup.periods;

s = snd_pcm_hw_param_value_max(slave_params, SNDRV_PCM_HW_PARAM_PERIODS, NULL);
- if (runtime->oss.maxfrags && s > runtime->oss.maxfrags)
+ if (s > 0 && runtime->oss.maxfrags && s > runtime->oss.maxfrags)
s = runtime->oss.maxfrags;
if (oss_periods > s)
oss_periods = s;