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staging: line6: alloc/free buffers in hw_params/hw_free 

It is unsafe to free buffers in line6_pcm_stop(), which is not allowed
to sleep, since urbs cannot be killed completely there and only
unlinked.  This means I/O may still be in progress and the URB
completion function still gets invoked.  This may result in memory
corruption when buffer_in is freed but I/O is still pending.

Additionally, line6_pcm_start() is not supposed to sleep so it should
not use kmalloc(GFP_KERNEL).

These issues can be resolved by performing buffer allocation/freeing in
the .hw_params/.hw_free callbacks instead.  The ALSA documentation also
recommends doing buffer allocation/freeing in these callbacks.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Stefan Hajnoczi 2011-11-23 08:20:45 +00:00 committed by Greg Kroah-Hartman
parent 3b08db37cb
commit 140e28b83c
3 changed files with 30 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/staging/line6/capture.c
View File

@ -9,6 +9,7 @@
*
*/
#include <linux/slab.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
@ -319,6 +320,15 @@ static int snd_line6_capture_hw_params(struct snd_pcm_substream *substream,
}
/* -- [FD] end */
line6pcm->buffer_in = kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
line6pcm->max_packet_size, GFP_KERNEL);
if (!line6pcm->buffer_in) {
dev_err(line6pcm->line6->ifcdev,
"cannot malloc capture buffer\n");
return -ENOMEM;
}
ret = snd_pcm_lib_malloc_pages(substream,
params_buffer_bytes(hw_params));
if (ret < 0)
@ -331,6 +341,11 @@ static int snd_line6_capture_hw_params(struct snd_pcm_substream *substream,
/* hw_free capture callback */
static int snd_line6_capture_hw_free(struct snd_pcm_substream *substream)
{
struct snd_line6_pcm *line6pcm = snd_pcm_substream_chip(substream);
line6_unlink_wait_clear_audio_in_urbs(line6pcm);
kfree(line6pcm->buffer_in);
line6pcm->buffer_in = NULL;
return snd_pcm_lib_free_pages(substream);
}

24
drivers/staging/line6/pcm.c
View File

@ -119,16 +119,6 @@ int line6_pcm_start(struct snd_line6_pcm *line6pcm, int channels)
if (line6pcm->active_urb_in | line6pcm->unlink_urb_in)
return -EBUSY;
line6pcm->buffer_in =
kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
line6pcm->max_packet_size, GFP_KERNEL);
if (!line6pcm->buffer_in) {
dev_err(line6pcm->line6->ifcdev,
"cannot malloc capture buffer\n");
return -ENOMEM;
}
line6pcm->count_in = 0;
line6pcm->prev_fsize = 0;
err = line6_submit_audio_in_all_urbs(line6pcm);
@ -147,16 +137,6 @@ int line6_pcm_start(struct snd_line6_pcm *line6pcm, int channels)
if (line6pcm->active_urb_out | line6pcm->unlink_urb_out)
return -EBUSY;
line6pcm->buffer_out =
kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
line6pcm->max_packet_size, GFP_KERNEL);
if (!line6pcm->buffer_out) {
dev_err(line6pcm->line6->ifcdev,
"cannot malloc playback buffer\n");
return -ENOMEM;
}
line6pcm->count_out = 0;
err = line6_submit_audio_out_all_urbs(line6pcm);
@ -178,15 +158,11 @@ int line6_pcm_stop(struct snd_line6_pcm *line6pcm, int channels)
if (((flags_old & MASK_CAPTURE) != 0) &&
((flags_new & MASK_CAPTURE) == 0)) {
line6_unlink_audio_in_urbs(line6pcm);
kfree(line6pcm->buffer_in);
line6pcm->buffer_in = NULL;
}
if (((flags_old & MASK_PLAYBACK) != 0) &&
((flags_new & MASK_PLAYBACK) == 0)) {
line6_unlink_audio_out_urbs(line6pcm);
kfree(line6pcm->buffer_out);
line6pcm->buffer_out = NULL;
}
#if LINE6_BACKUP_MONITOR_SIGNAL
kfree(line6pcm->prev_fbuf);

15
drivers/staging/line6/playback.c
View File

@ -9,6 +9,7 @@
*
*/
#include <linux/slab.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
@ -469,6 +470,15 @@ static int snd_line6_playback_hw_params(struct snd_pcm_substream *substream,
}
/* -- [FD] end */
line6pcm->buffer_out = kmalloc(LINE6_ISO_BUFFERS * LINE6_ISO_PACKETS *
line6pcm->max_packet_size, GFP_KERNEL);
if (!line6pcm->buffer_out) {
dev_err(line6pcm->line6->ifcdev,
"cannot malloc playback buffer\n");
return -ENOMEM;
}
ret = snd_pcm_lib_malloc_pages(substream,
params_buffer_bytes(hw_params));
if (ret < 0)
@ -481,6 +491,11 @@ static int snd_line6_playback_hw_params(struct snd_pcm_substream *substream,
/* hw_free playback callback */
static int snd_line6_playback_hw_free(struct snd_pcm_substream *substream)
{
struct snd_line6_pcm *line6pcm = snd_pcm_substream_chip(substream);
line6_unlink_wait_clear_audio_out_urbs(line6pcm);
kfree(line6pcm->buffer_out);
line6pcm->buffer_out = NULL;
return snd_pcm_lib_free_pages(substream);
}