FAILED: patch "[PATCH] ASoC: SOF: ipc4-topology: Fix shift-out-of-bounds for" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 746de48c3a250f0c264105dcbfcdf0c5001e970b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026102124-wisdom-print-3a6c@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 746de48c3a250f0c264105dcbfcdf0c5001e970b Mon Sep 17 00:00:00 2001
From: Peter Ujfalusi <[email protected]>
Date: Thu, 8 Oct 2026 12:01:30 +0300
Subject: [PATCH] ASoC: SOF: ipc4-topology: Fix shift-out-of-bounds for
aggregated ALH capture

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.

index 24a1175dd690..22c15fbb93f2 100644
@@ -2458,11 +2458,14 @@ _sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 				ch_map >>= 4;
 			}
 
-			if (swidget->id == snd_soc_dapm_dai_in && ch_count == out_ref_channels) {
+			if ((swidget->id == snd_soc_dapm_dai_in && ch_count == out_ref_channels) ||
+			    ch_count < blob->alh_cfg.device_count) {
 				/*
 				 * For playback DAI widgets where the channel number is equal to
-				 * the output reference channels, set the step = 0 to ensure all
-				 * the ch_mask is applied to all alh mappings.
+				 * the output reference channels, or 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;

From: Peter Ujfalusi <[email protected]>

[ 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.

---
 sound/soc/sof/ipc4-topology.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

index 5701e4d1ac130..7178279ddfb77 100644
@@ -2286,8 +2286,20 @@ 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