From: Stefan Hajnoczi <stefanha@xxxxxxxxx>
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.
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@xxxxxxxxx>
---
capture.c | 15 +++++++++++++++
pcm.c | 24 ------------------------
playback.c | 15 +++++++++++++++
3 files changed, 30 insertions(+), 24 deletions(-)
diff --git a/capture.c b/capture.c
index 9647154..d9da7ed 100644
--- a/capture.c
+++ b/capture.c
@@ -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);
}
diff --git a/pcm.c b/pcm.c
index a8bdc6d..7e3a5f0 100644
--- a/pcm.c
+++ b/pcm.c
@@ -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_ATOMIC);
-
- 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_ATOMIC);
-
- 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);
diff --git a/playback.c b/playback.c
index 10c5438..b344527 100644
--- a/playback.c
+++ b/playback.c
@@ -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);
}
--
1.7.7.1
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