On Tue, 30 Nov 2021 12:39:27 +0100,
Takashi Iwai wrote:
On Tue, 30 Nov 2021 12:16:18 +0100,
Bixuan Cui wrote:
The commit 7661809d493b ("mm: don't allow oversized kvmalloc()
calls") limits the max allocatable memory via kvzalloc() to MAX_INT.
Reported-by:syzbot+bb348e9f9a954d42746f@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Bixuan Cui<cuibixuan@xxxxxxxxxxxxxxxxx>
We should check the allocation size a lot earlier than here.
IOW, such a big size shouldn't have been passed to this function but
it should have been handled as an error in the caller side
(snd_pcm_oss_change_params*()).
Could you give the reproducer?
I'm asking it because the patch like below might cover the case.
Takashi
-- 8< --
From: Takashi Iwai<tiwai@xxxxxxx>
Subject: [PATCH] ALSA: pcm: oss: Fix negative period/buffer sizes
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.
Signed-off-by: Takashi Iwai<tiwai@xxxxxxx>
---
sound/core/oss/pcm_oss.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 82a818734a5f..bec7590bc84b 100644
--- 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 snd_pcm_hw_params *params,
*
* 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(struct snd_pcm_substream *substream,
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(struct snd_pcm_substream *substream,
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(struct snd_pcm_substream *substream,
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(struct snd_pcm_substream *substream,
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;
