[PATCH 6.12.y] ASoC: SOF: ipc4-topology: Fix shift-out-of-bounds for aggregated ALH capture

[Sasha Levin <sashal@kernel.org>]

From: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

[ Upstream commit 746de48c3a250f0c264105dcbfcdf0c5001e970b ]

When ch_count is smaller than blob->alh_cfg.device_count (e.g. a mono
capture stream, such as a SmartMic, aggregated across multiple SDW
links), step = ch_count / blob->alh_cfg.device_count truncates to 0.
The subsequent GENMASK(step - 1, 0) then underflows step - 1 (u32) to
UINT_MAX, causing GENMASK()'s internal shift to use an out-of-bounds
exponent:

  UBSAN: shift-out-of-bounds in sound/soc/sof/ipc4-topology.c:2363:13
  shift exponent 18446744069414584384 is too large for 64-bit type 'long unsigned int'

Treat ch_count < device_count the same way as the existing "channels
equal to output reference channels" case: apply the same ch_mask to
every aggregated device instead of trying to split channels that
can't be evenly divided.

Fixes: 0390a102cc18 ("ASoC: SOF: ipc4-topology: use different channel mask for each sdw amp feedback")
Cc: stable@vger.kernel.org
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Link: https://patch.msgid.link/20261008090130.15135-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
[ sashal: used a standalone condition because the playback-specific channel check is absent ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 sound/soc/sof/ipc4-topology.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/sound/soc/sof/ipc4-topology.c b/sound/soc/sof/ipc4-topology.c
index 6af0cc154f3d7..5cf272fe93ff6 100644
--- a/sound/soc/sof/ipc4-topology.c
+++ b/sound/soc/sof/ipc4-topology.c
@@ -1973,8 +1973,20 @@ sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 				ch_map >>= 4;
 			}
 
-			step = ch_count / blob->alh_cfg.device_count;
-			mask =  GENMASK(step - 1, 0);
+			if (ch_count < blob->alh_cfg.device_count) {
+				/*
+				 * When there are fewer channels than aggregated devices
+				 * (e.g. a mono capture stream split across multiple links),
+				 * set step = 0 to ensure all the ch_mask is applied to all
+				 * alh mappings.
+				 */
+				mask = ch_mask;
+				step = 0;
+			} else {
+				step = ch_count / blob->alh_cfg.device_count;
+				mask =  GENMASK(step - 1, 0);
+			}
+
 			/*
 			 * Set each gtw_cfg.node_id to blob->alh_cfg.mapping[]
 			 * for all widgets with the same stream name
-- 
2.53.0