ASoC: stm32: spdifrx: fix race condition in irq handler

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

Fixes: 03e4d5d5 ("ASoC: stm32: Add SPDIFRX support")
Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Link: https://lore.kernel.org/r/20191204154333.7152-3-olivier.moysan@st.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/stm/stm32_spdifrx.c

@@ -220,6 +220,7 @@
  * @slave_config: dma slave channel runtime config pointer
  * @phys_addr: SPDIFRX registers physical base address
  * @lock: synchronization enabling lock
+ * @irq_lock: prevent race condition with IRQ on stream state
  * @cs: channel status buffer
  * @ub: user data buffer
  * @irq: SPDIFRX interrupt line
@@ -240,6 +241,7 @@ struct stm32_spdifrx_data {
 	struct dma_slave_config slave_config;
 	dma_addr_t phys_addr;
 	spinlock_t lock;  /* Sync enabling lock */
+	spinlock_t irq_lock; /* Prevent race condition on stream state */
 	unsigned char cs[SPDIFRX_CS_BYTES_NB];
 	unsigned char ub[SPDIFRX_UB_BYTES_NB];
 	int irq;
@@ -667,7 +669,6 @@ static const struct regmap_config stm32_h7_spdifrx_regmap_conf = {
 static irqreturn_t stm32_spdifrx_isr(int irq, void *devid)
 {
 	struct stm32_spdifrx_data *spdifrx = (struct stm32_spdifrx_data *)devid;
-	struct snd_pcm_substream *substream = spdifrx->substream;
 	struct platform_device *pdev = spdifrx->pdev;
 	unsigned int cr, mask, sr, imr;
 	unsigned int flags, sync_state;
@@ -747,14 +748,19 @@ static irqreturn_t stm32_spdifrx_isr(int irq, void *devid)
 			return IRQ_HANDLED;
 		}
 
-		if (substream)
-			snd_pcm_stop(substream, SNDRV_PCM_STATE_DISCONNECTED);
+		spin_lock(&spdifrx->irq_lock);
+		if (spdifrx->substream)
+			snd_pcm_stop(spdifrx->substream,
+				     SNDRV_PCM_STATE_DISCONNECTED);
+		spin_unlock(&spdifrx->irq_lock);
 
 		return IRQ_HANDLED;
 	}
 
-	if (err_xrun && substream)
-		snd_pcm_stop_xrun(substream);
+	spin_lock(&spdifrx->irq_lock);
+	if (err_xrun && spdifrx->substream)
+		snd_pcm_stop_xrun(spdifrx->substream);
+	spin_unlock(&spdifrx->irq_lock);
 
 	return IRQ_HANDLED;
 }
@@ -763,9 +769,12 @@ static int stm32_spdifrx_startup(struct snd_pcm_substream *substream,
 				 struct snd_soc_dai *cpu_dai)
 {
 	struct stm32_spdifrx_data *spdifrx = snd_soc_dai_get_drvdata(cpu_dai);
+	unsigned long flags;
 	int ret;
 
+	spin_lock_irqsave(&spdifrx->irq_lock, flags);
 	spdifrx->substream = substream;
+	spin_unlock_irqrestore(&spdifrx->irq_lock, flags);
 
 	ret = clk_prepare_enable(spdifrx->kclk);
 	if (ret)
@@ -841,8 +850,12 @@ static void stm32_spdifrx_shutdown(struct snd_pcm_substream *substream,
 				   struct snd_soc_dai *cpu_dai)
 {
 	struct stm32_spdifrx_data *spdifrx = snd_soc_dai_get_drvdata(cpu_dai);
+	unsigned long flags;
 
+	spin_lock_irqsave(&spdifrx->irq_lock, flags);
 	spdifrx->substream = NULL;
+	spin_unlock_irqrestore(&spdifrx->irq_lock, flags);
+
 	clk_disable_unprepare(spdifrx->kclk);
 }
 
@@ -946,6 +959,7 @@ static int stm32_spdifrx_probe(struct platform_device *pdev)
 	spdifrx->pdev = pdev;
 	init_completion(&spdifrx->cs_completion);
 	spin_lock_init(&spdifrx->lock);
+	spin_lock_init(&spdifrx->irq_lock);
 
 	platform_set_drvdata(pdev, spdifrx);