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>
---
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);
--
2.34.1
