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Subject[PATCH] snd_pcm_oss_change_params is a stack offender
On Thu, Feb 20, 2003 at 08:54:55AM -0800, Linus Torvalds wrote:

> Ok, the 4kB stack definitely won't work in real life, but that's because
> we have some hopelessly bad stack users in the kernel. But the debugging
> part would be good to try (in fact, it might be a good idea to keep the
> 8kB stack, but with rather anal debugging. Just the "mcount" part should
> do that).
>
> A sorted list of bad stack users (more than 256 bytes) in my default build
> follows. Anybody can create their own with something like
>
> objdump -d linux/vmlinux |
> grep 'sub.*$0x...,.*esp' |
> awk '{ print $9,$1 }' |
> sort > bigstack
>
> and a script to look up the addresses.
>
[snipped]

> 0xc02ae062 <ide_unregister+8>: sub $0x8c4,%esp
> 0xc010535d <huft_build+9>: sub $0x5b0,%esp
> 0xc0326a53 <snd_pcm_oss_change_params+6>: sub $0x590,%esp

Here's a quick patch to fix the third worst offender,
snd_pcm_oss_change_params. Compiles fine but not tested yet.

# sound/core/oss/pcm_oss.c 1.20 -> 1.21
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/02/21 mulix@alhambra.mulix.org 1.1007
# snd_pcm_oss_change_params was a stack offender, having three large
# structs on the stack. Allocate those structs on the heap and change
# the code accordingly.
# --------------------------------------------
#
diff -Nru a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
--- a/sound/core/oss/pcm_oss.c Fri Feb 21 09:35:24 2003
+++ b/sound/core/oss/pcm_oss.c Fri Feb 21 09:35:24 2003
@@ -291,11 +291,51 @@
return snd_pcm_hw_param_near(substream, params, SNDRV_PCM_HW_PARAM_RATE, best_rate, 0);
}

+static int alloc_param_structs(snd_pcm_hw_params_t** params,
+ snd_pcm_hw_params_t** sparams,
+ snd_pcm_sw_params_t** sw_params)
+{
+ snd_pcm_hw_params_t* hwp;
+ snd_pcm_sw_params_t* swp;
+
+ if (!(hwp = kmalloc(sizeof(*hwp), GFP_KERNEL)))
+ goto out;
+
+ memset(hwp, 0, sizeof(*hwp));
+ *params = hwp;
+
+ if (!(hwp = kmalloc(sizeof(*hwp), GFP_KERNEL)))
+ goto free_params;
+
+ memset(hwp, 0, sizeof(*hwp));
+ *sparams = hwp;
+
+ if (!(swp = kmalloc(sizeof(*swp), GFP_KERNEL)))
+ goto free_sparams;
+
+ memset(swp, 0, sizeof(*swp));
+ *sw_params = swp;
+
+ return 0;
+
+ free_sparams:
+ kfree(*sparams);
+ *sparams = NULL;
+
+ free_params:
+ kfree(*params);
+ *params = NULL;
+
+ out:
+ return -ENOMEM;
+}
+
+
static int snd_pcm_oss_change_params(snd_pcm_substream_t *substream)
{
snd_pcm_runtime_t *runtime = substream->runtime;
- snd_pcm_hw_params_t params, sparams;
- snd_pcm_sw_params_t sw_params;
+ snd_pcm_hw_params_t *params, *sparams;
+ snd_pcm_sw_params_t *sw_params;
ssize_t oss_buffer_size, oss_period_size;
size_t oss_frame_size;
int err;
@@ -311,9 +351,14 @@
direct = (setup != NULL && setup->direct);
}

- _snd_pcm_hw_params_any(&sparams);
- _snd_pcm_hw_param_setinteger(&sparams, SNDRV_PCM_HW_PARAM_PERIODS);
- _snd_pcm_hw_param_min(&sparams, SNDRV_PCM_HW_PARAM_PERIODS, 2, 0);
+ if ((err = alloc_param_structs(&params, &sparams, &sw_params))) {
+ snd_printd("out of memory\n");
+ return err;
+ }
+
+ _snd_pcm_hw_params_any(sparams);
+ _snd_pcm_hw_param_setinteger(sparams, SNDRV_PCM_HW_PARAM_PERIODS);
+ _snd_pcm_hw_param_min(sparams, SNDRV_PCM_HW_PARAM_PERIODS, 2, 0);
snd_mask_none(&mask);
if (atomic_read(&runtime->mmap_count))
snd_mask_set(&mask, SNDRV_PCM_ACCESS_MMAP_INTERLEAVED);
@@ -322,17 +367,17 @@
if (!direct)
snd_mask_set(&mask, SNDRV_PCM_ACCESS_RW_NONINTERLEAVED);
}
- err = snd_pcm_hw_param_mask(substream, &sparams, SNDRV_PCM_HW_PARAM_ACCESS, &mask);
+ err = snd_pcm_hw_param_mask(substream, sparams, SNDRV_PCM_HW_PARAM_ACCESS, &mask);
if (err < 0) {
snd_printd("No usable accesses\n");
return -EINVAL;
}
- choose_rate(substream, &sparams, runtime->oss.rate);
- snd_pcm_hw_param_near(substream, &sparams, SNDRV_PCM_HW_PARAM_CHANNELS, runtime->oss.channels, 0);
+ choose_rate(substream, sparams, runtime->oss.rate);
+ snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_CHANNELS, runtime->oss.channels, 0);

format = snd_pcm_oss_format_from(runtime->oss.format);

- sformat_mask = *hw_param_mask(&sparams, SNDRV_PCM_HW_PARAM_FORMAT);
+ sformat_mask = *hw_param_mask(sparams, SNDRV_PCM_HW_PARAM_FORMAT);
if (direct)
sformat = format;
else
@@ -349,46 +394,46 @@
return -EINVAL;
}
}
- err = _snd_pcm_hw_param_set(&sparams, SNDRV_PCM_HW_PARAM_FORMAT, sformat, 0);
+ err = _snd_pcm_hw_param_set(sparams, SNDRV_PCM_HW_PARAM_FORMAT, sformat, 0);
snd_assert(err >= 0, return err);

if (direct) {
- params = sparams;
+ memcpy(params, sparams, sizeof(*params));
} else {
- _snd_pcm_hw_params_any(&params);
- _snd_pcm_hw_param_set(&params, SNDRV_PCM_HW_PARAM_ACCESS,
+ _snd_pcm_hw_params_any(params);
+ _snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_ACCESS,
SNDRV_PCM_ACCESS_RW_INTERLEAVED, 0);
- _snd_pcm_hw_param_set(&params, SNDRV_PCM_HW_PARAM_FORMAT,
+ _snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_FORMAT,
snd_pcm_oss_format_from(runtime->oss.format), 0);
- _snd_pcm_hw_param_set(&params, SNDRV_PCM_HW_PARAM_CHANNELS,
+ _snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_CHANNELS,
runtime->oss.channels, 0);
- _snd_pcm_hw_param_set(&params, SNDRV_PCM_HW_PARAM_RATE,
+ _snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_RATE,
runtime->oss.rate, 0);
pdprintf("client: access = %i, format = %i, channels = %i, rate = %i\n",
- params_access(&params), params_format(&params),
- params_channels(&params), params_rate(&params));
+ params_access(params), params_format(params),
+ params_channels(params), params_rate(params));
}
pdprintf("slave: access = %i, format = %i, channels = %i, rate = %i\n",
- params_access(&sparams), params_format(&sparams),
- params_channels(&sparams), params_rate(&sparams));
+ params_access(sparams), params_format(sparams),
+ params_channels(sparams), params_rate(sparams));

- oss_frame_size = snd_pcm_format_physical_width(params_format(&params)) *
- params_channels(&params) / 8;
+ oss_frame_size = snd_pcm_format_physical_width(params_format(params)) *
+ params_channels(params) / 8;

snd_pcm_oss_plugin_clear(substream);
if (!direct) {
/* add necessary plugins */
snd_pcm_oss_plugin_clear(substream);
if ((err = snd_pcm_plug_format_plugins(substream,
- &params,
- &sparams)) < 0) {
+ params,
+ sparams)) < 0) {
snd_printd("snd_pcm_plug_format_plugins failed: %i\n", err);
snd_pcm_oss_plugin_clear(substream);
return err;
}
if (runtime->oss.plugin_first) {
snd_pcm_plugin_t *plugin;
- if ((err = snd_pcm_plugin_build_io(substream, &sparams, &plugin)) < 0) {
+ if ((err = snd_pcm_plugin_build_io(substream, sparams, &plugin)) < 0) {
snd_printd("snd_pcm_plugin_build_io failed: %i\n", err);
snd_pcm_oss_plugin_clear(substream);
return err;
@@ -405,51 +450,50 @@
}
}

- err = snd_pcm_oss_period_size(substream, &params, &sparams);
+ err = snd_pcm_oss_period_size(substream, params, sparams);
if (err < 0)
return err;

n = snd_pcm_plug_slave_size(substream, runtime->oss.period_bytes / oss_frame_size);
- err = snd_pcm_hw_param_near(substream, &sparams, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, n, 0);
+ err = snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_PERIOD_SIZE, n, 0);
snd_assert(err >= 0, return err);

- err = snd_pcm_hw_param_near(substream, &sparams, SNDRV_PCM_HW_PARAM_PERIODS,
+ err = snd_pcm_hw_param_near(substream, sparams, SNDRV_PCM_HW_PARAM_PERIODS,
runtime->oss.periods, 0);
snd_assert(err >= 0, return err);

snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, 0);

- if ((err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_HW_PARAMS, &sparams)) < 0) {
+ if ((err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_HW_PARAMS, sparams)) < 0) {
snd_printd("HW_PARAMS failed: %i\n", err);
return err;
}

- memset(&sw_params, 0, sizeof(sw_params));
if (runtime->oss.trigger) {
- sw_params.start_threshold = 1;
+ sw_params->start_threshold = 1;
} else {
- sw_params.start_threshold = runtime->boundary;
+ sw_params->start_threshold = runtime->boundary;
}
if (atomic_read(&runtime->mmap_count))
- sw_params.stop_threshold = runtime->boundary;
+ sw_params->stop_threshold = runtime->boundary;
else
- sw_params.stop_threshold = runtime->buffer_size;
- sw_params.tstamp_mode = SNDRV_PCM_TSTAMP_NONE;
- sw_params.period_step = 1;
- sw_params.sleep_min = 0;
- sw_params.avail_min = runtime->period_size;
- sw_params.xfer_align = 1;
- sw_params.silence_threshold = 0;
- sw_params.silence_size = 0;
+ sw_params->stop_threshold = runtime->buffer_size;
+ sw_params->tstamp_mode = SNDRV_PCM_TSTAMP_NONE;
+ sw_params->period_step = 1;
+ sw_params->sleep_min = 0;
+ sw_params->avail_min = runtime->period_size;
+ sw_params->xfer_align = 1;
+ sw_params->silence_threshold = 0;
+ sw_params->silence_size = 0;

- if ((err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_SW_PARAMS, &sw_params)) < 0) {
+ if ((err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_SW_PARAMS, sw_params)) < 0) {
snd_printd("SW_PARAMS failed: %i\n", err);
return err;
}
runtime->control->avail_min = runtime->period_size;

- runtime->oss.periods = params_periods(&sparams);
- oss_period_size = snd_pcm_plug_client_size(substream, params_period_size(&sparams));
+ runtime->oss.periods = params_periods(sparams);
+ oss_period_size = snd_pcm_plug_client_size(substream, params_period_size(sparams));
snd_assert(oss_period_size >= 0, return -EINVAL);
if (runtime->oss.plugin_first) {
err = snd_pcm_plug_alloc(substream, oss_period_size);
@@ -468,12 +512,12 @@
runtime->oss.period_bytes,
runtime->oss.buffer_bytes);
pdprintf("slave: period_size = %i, buffer_size = %i\n",
- params_period_size(&sparams),
- params_buffer_size(&sparams));
+ params_period_size(sparams),
+ params_buffer_size(sparams));

- runtime->oss.format = snd_pcm_oss_format_to(params_format(&params));
- runtime->oss.channels = params_channels(&params);
- runtime->oss.rate = params_rate(&params);
+ runtime->oss.format = snd_pcm_oss_format_to(params_format(params));
+ runtime->oss.channels = params_channels(params);
+ runtime->oss.rate = params_rate(params);

runtime->oss.params = 0;
runtime->oss.prepare = 1;

--
Muli Ben-Yehuda
http://www.mulix.org

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