[PATCH 6/7] ASoC: stm32: i2s: fix race condition in irq handler

From: Olivier Moysan
Date: Tue Feb 26 2019 - 08:51:46 EST


When snd_pcm_stop_xrun() is called in interrupt routine,
substream context may have already been released.
Add protection on substream context.

Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxx>
---
sound/soc/stm/stm32_i2s.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/sound/soc/stm/stm32_i2s.c b/sound/soc/stm/stm32_i2s.c
index 9edb753ffa1b..42ce87a35104 100644
--- a/sound/soc/stm/stm32_i2s.c
+++ b/sound/soc/stm/stm32_i2s.c
@@ -201,6 +201,7 @@ enum i2s_datlen {
* @base: mmio register base virtual address
* @phys_addr: I2S registers physical base address
* @lock_fd: lock to manage race conditions in full duplex mode
+ * @irq_lock: prevent race condition with IRQ
* @dais_name: DAI name
* @mclk_rate: master clock frequency (Hz)
* @fmt: DAI protocol
@@ -222,6 +223,7 @@ struct stm32_i2s_data {
void __iomem *base;
dma_addr_t phys_addr;
spinlock_t lock_fd; /* Manage race conditions for full duplex */
+ spinlock_t irq_lock; /* used to prevent race condition with IRQ */
char dais_name[STM32_I2S_DAI_NAME_SIZE];
unsigned int mclk_rate;
unsigned int fmt;
@@ -263,8 +265,10 @@ static irqreturn_t stm32_i2s_isr(int irq, void *devid)
if (flags & I2S_SR_TIFRE)
dev_dbg(&pdev->dev, "Frame error\n");

- if (err)
+ spin_lock(&i2s->irq_lock);
+ if (err && i2s->substream)
snd_pcm_stop_xrun(i2s->substream);
+ spin_unlock(&i2s->irq_lock);

return IRQ_HANDLED;
}
@@ -540,9 +544,12 @@ static int stm32_i2s_startup(struct snd_pcm_substream *substream,
struct snd_soc_dai *cpu_dai)
{
struct stm32_i2s_data *i2s = snd_soc_dai_get_drvdata(cpu_dai);
+ unsigned long flags;
int ret;

+ spin_lock_irqsave(&i2s->irq_lock, flags);
i2s->substream = substream;
+ spin_unlock_irqrestore(&i2s->irq_lock, flags);

ret = clk_prepare_enable(i2s->i2sclk);
if (ret < 0) {
@@ -673,13 +680,16 @@ static void stm32_i2s_shutdown(struct snd_pcm_substream *substream,
struct snd_soc_dai *cpu_dai)
{
struct stm32_i2s_data *i2s = snd_soc_dai_get_drvdata(cpu_dai);
-
- i2s->substream = NULL;
+ unsigned long flags;

regmap_update_bits(i2s->regmap, STM32_I2S_CGFR_REG,
I2S_CGFR_MCKOE, (unsigned int)~I2S_CGFR_MCKOE);

clk_disable_unprepare(i2s->i2sclk);
+
+ spin_lock_irqsave(&i2s->irq_lock, flags);
+ i2s->substream = NULL;
+ spin_unlock_irqrestore(&i2s->irq_lock, flags);
}

static int stm32_i2s_dai_probe(struct snd_soc_dai *cpu_dai)
@@ -874,6 +884,7 @@ static int stm32_i2s_probe(struct platform_device *pdev)
i2s->pdev = pdev;
i2s->ms_flg = I2S_MS_NOT_SET;
spin_lock_init(&i2s->lock_fd);
+ spin_lock_init(&i2s->irq_lock);
platform_set_drvdata(pdev, i2s);

ret = stm32_i2s_dais_init(pdev, i2s);
--
2.7.4