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SubjectRe: [INTERNAL][PATCH 4/7] ASoC: stm32: sai: fix stop management in isr
On Thu, 19 Oct 2017 15:03:20 +0200,
Olivier Moysan wrote:
>
> Add check on substream validity.
>
> Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
> ---
> sound/soc/stm/stm32_sai_sub.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
> index 2af397d..815ef10 100644
> --- a/sound/soc/stm/stm32_sai_sub.c
> +++ b/sound/soc/stm/stm32_sai_sub.c
> @@ -184,7 +184,6 @@ static bool stm32_sai_sub_writeable_reg(struct device *dev, unsigned int reg)
> static irqreturn_t stm32_sai_isr(int irq, void *devid)
> {
> struct stm32_sai_sub_data *sai = (struct stm32_sai_sub_data *)devid;
> - struct snd_pcm_substream *substream = sai->substream;
> struct platform_device *pdev = sai->pdev;
> unsigned int sr, imr, flags;
> snd_pcm_state_t status = SNDRV_PCM_STATE_RUNNING;
> @@ -199,6 +198,11 @@ static irqreturn_t stm32_sai_isr(int irq, void *devid)
> regmap_update_bits(sai->regmap, STM_SAI_CLRFR_REGX, SAI_XCLRFR_MASK,
> SAI_XCLRFR_MASK);
>
> + if (!sai->substream) {
> + dev_err(&pdev->dev, "Device stopped. Spurious IRQ 0x%x\n", sr);
> + return IRQ_NONE;
> + }
> +
> if (flags & SAI_XIMR_OVRUDRIE) {
> dev_err(&pdev->dev, "IRQ %s\n",
> STM_SAI_IS_PLAYBACK(sai) ? "underrun" : "overrun");
> @@ -227,9 +231,9 @@ static irqreturn_t stm32_sai_isr(int irq, void *devid)
> }
>
> if (status != SNDRV_PCM_STATE_RUNNING) {
> - snd_pcm_stream_lock(substream);
> - snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
> - snd_pcm_stream_unlock(substream);
> + snd_pcm_stream_lock(sai->substream);
> + snd_pcm_stop(sai->substream, SNDRV_PCM_STATE_XRUN);
> + snd_pcm_stream_unlock(sai->substream);

Actually changing to sai->substream opens a race, so this chunk is a
bad move, at least. We have no protection of sai->substream in this
context, thus it can hit a NULL dereference...


thanks,

Takashi

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