[PATCH 4.14 142/159] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Jiada Wang 


[ Upstream commit 33f801366bdf3f8b67dfe325b84f4051a090d01e ]

Currently there is race condition between set of byte_pos and wrap
it around when new buffer starts. If .pointer is called in-between
it will result in inconsistent pointer position be returned
from .pointer callback.

This patch increments buffer pointer atomically to avoid this issue.

Signed-off-by: Jiada Wang 
Reviewed-by: Takashi Sakamoto 
Acked-by: Kuninori Morimoto 
Signed-off-by: Mark Brown 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman 
---
 sound/soc/sh/rcar/ssi.c |   16 ++--
 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/sound/soc/sh/rcar/ssi.c
+++ b/sound/soc/sh/rcar/ssi.c
@@ -449,25 +449,29 @@ static bool rsnd_ssi_pointer_update(stru
int byte)
 {
struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
+   bool ret = false;
+   int byte_pos;
 
-   ssi->byte_pos += byte;
+   byte_pos = ssi->byte_pos + byte;
 
-   if (ssi->byte_pos >= ssi->next_period_byte) {
+   if (byte_pos >= ssi->next_period_byte) {
struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
 
ssi->period_pos++;
ssi->next_period_byte += ssi->byte_per_period;
 
if (ssi->period_pos >= runtime->periods) {
-   ssi->byte_pos = 0;
+   byte_pos = 0;
ssi->period_pos = 0;
ssi->next_period_byte = ssi->byte_per_period;
}
 
-   return true;
+   ret = true;
}
 
-   return false;
+   WRITE_ONCE(ssi->byte_pos, byte_pos);
+
+   return ret;
 }
 
 /*
@@ -838,7 +842,7 @@ static int rsnd_ssi_pointer(struct rsnd_
struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
 
-   *pointer = bytes_to_frames(runtime, ssi->byte_pos);
+   *pointer = bytes_to_frames(runtime, READ_ONCE(ssi->byte_pos));
 
return 0;
 }

[PATCH 4.14 142/159] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

--

From: Jiada Wang 


[ Upstream commit 33f801366bdf3f8b67dfe325b84f4051a090d01e ]

Currently there is race condition between set of byte_pos and wrap
it around when new buffer starts. If .pointer is called in-between
it will result in inconsistent pointer position be returned
from .pointer callback.

This patch increments buffer pointer atomically to avoid this issue.

Signed-off-by: Jiada Wang 
Reviewed-by: Takashi Sakamoto 
Acked-by: Kuninori Morimoto 
Signed-off-by: Mark Brown 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman 
---
 sound/soc/sh/rcar/ssi.c |   16 ++--
 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/sound/soc/sh/rcar/ssi.c
+++ b/sound/soc/sh/rcar/ssi.c
@@ -449,25 +449,29 @@ static bool rsnd_ssi_pointer_update(stru
int byte)
 {
struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
+   bool ret = false;
+   int byte_pos;
 
-   ssi->byte_pos += byte;
+   byte_pos = ssi->byte_pos + byte;
 
-   if (ssi->byte_pos >= ssi->next_period_byte) {
+   if (byte_pos >= ssi->next_period_byte) {
struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
 
ssi->period_pos++;
ssi->next_period_byte += ssi->byte_per_period;
 
if (ssi->period_pos >= runtime->periods) {
-   ssi->byte_pos = 0;
+   byte_pos = 0;
ssi->period_pos = 0;
ssi->next_period_byte = ssi->byte_per_period;
}
 
-   return true;
+   ret = true;
}
 
-   return false;
+   WRITE_ONCE(ssi->byte_pos, byte_pos);
+
+   return ret;
 }
 
 /*
@@ -838,7 +842,7 @@ static int rsnd_ssi_pointer(struct rsnd_
struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
 
-   *pointer = bytes_to_frames(runtime, ssi->byte_pos);
+   *pointer = bytes_to_frames(runtime, READ_ONCE(ssi->byte_pos));
 
return 0;
 }