On 11/24/23 12:01, Krzysztof Kozlowski wrote:
> If bus is marked as multi_link, but number of masters in the stream is
> not higher than bus->hw_sync_min_links (bus->multi_link && m_rt_count >=
> bus->hw_sync_min_links), bank switching should not happen. The first
> part of do_bank_switch() code properly takes these conditions into
> account, but second part (sdw_ml_sync_bank_switch()) relies purely on
> bus->multi_link property. This is not balanced and leads to NULL
> pointer dereference:
>
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> ...
> Call trace:
> wait_for_completion_timeout+0x124/0x1f0
> do_bank_switch+0x370/0x6f8
> sdw_prepare_stream+0x2d0/0x438
> qcom_snd_sdw_prepare+0xa0/0x118
> sm8450_snd_prepare+0x128/0x148
> snd_soc_link_prepare+0x5c/0xe8
> __soc_pcm_prepare+0x28/0x1ec
> dpcm_be_dai_prepare+0x1e0/0x2c0
> dpcm_fe_dai_prepare+0x108/0x28c
> snd_pcm_do_prepare+0x44/0x68
> snd_pcm_action_single+0x54/0xc0
> snd_pcm_action_nonatomic+0xe4/0xec
> snd_pcm_prepare+0xc4/0x114
> snd_pcm_common_ioctl+0x1154/0x1cc0
> snd_pcm_ioctl+0x54/0x74
>
> Fixes: ce6e74d008ff ("soundwire: Add support for multi link bank switch")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
LGTM, thanks for the patch.
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> ---
> drivers/soundwire/stream.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 9dc6399f206a..f9c0adc0738d 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -742,14 +742,15 @@ static int sdw_bank_switch(struct sdw_bus *bus, int m_rt_count)
> * sdw_ml_sync_bank_switch: Multilink register bank switch
> *
> * @bus: SDW bus instance
> + * @multi_link: whether this is a multi-link stream with hardware-based sync
> *
> * Caller function should free the buffers on error
> */
> -static int sdw_ml_sync_bank_switch(struct sdw_bus *bus)
> +static int sdw_ml_sync_bank_switch(struct sdw_bus *bus, bool multi_link)
> {
> unsigned long time_left;
>
> - if (!bus->multi_link)
> + if (!multi_link)
> return 0;
>
> /* Wait for completion of transfer */
> @@ -847,7 +848,7 @@ static int do_bank_switch(struct sdw_stream_runtime *stream)
> bus->bank_switch_timeout = DEFAULT_BANK_SWITCH_TIMEOUT;
>
> /* Check if bank switch was successful */
> - ret = sdw_ml_sync_bank_switch(bus);
> + ret = sdw_ml_sync_bank_switch(bus, multi_link);
> if (ret < 0) {
> dev_err(bus->dev,
> "multi link bank switch failed: %d\n", ret);
