FAILED: patch "[PATCH] ALSA: x86: hdmi: fix chmap array missing terminator entry" 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 f5e1a9a3fddab8421416b68bb132ae9626d07156
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026110457-overhung-helper-62a6@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From f5e1a9a3fddab8421416b68bb132ae9626d07156 Mon Sep 17 00:00:00 2001
From: Peter Ujfalusi <[email protected]>
Date: Thu, 8 Oct 2026 11:54:11 +0300
Subject: [PATCH] ALSA: x86: hdmi: fix chmap array missing terminator entry

had_build_channel_allocation_map() allocates a single struct snd_pcm_chmap_elem via kzalloc() and stores it as intelhaddata->chmap->chmap. struct snd_pcm_chmap.chmap is expected to be a zero-terminated array (see snd_pcm_std_chmaps[]), but had_register_chmap_ctls() never overrides the TLV callback installed by snd_pcm_add_chmap_ctls(), so the generic pcm_chmap_ctl_tlv() from ALSA core is left in place.

pcm_chmap_ctl_tlv() is reachable by any local user via SNDRV_CTL_IOCTL_TLV_READ on the "Playback Channel Map" control and walks the array with "for (map = info->chmap; map->channels; map++)". Since the driver's single element is never terminated, this walks past the allocation. The same pointer is also freed on hot-unplug and rebuilt on hot-plug under intelhaddata->mutex, while the TLV callback runs under card->controls_rwsem without that mutex, so the walk can also race a concurrent free of the array.

Fix this by allocating a second, zeroed element so the array is properly terminated, and by dropping the inherited TLV callback entirely at registration time, since the driver never implements one of its own.

index 9f67244d4946..542fc35ec9b7 100644
@@ -475,7 +475,8 @@ static void had_build_channel_allocation_map(struct snd_intelhad *intelhaddata)
 	kfree(intelhaddata->chmap->chmap);
 	intelhaddata->chmap->chmap = NULL;
 
-	chmap = kzalloc_obj(*chmap);
+	/* info->chmap must be zero-terminated; allocate a spare terminator entry */
+	chmap = kzalloc_objs(*chmap, 2);
 	if (!chmap)
 		return;
 

@@ -575,6 +576,12 @@ static int had_register_chmap_ctls(struct snd_intelhad *intelhaddata,
 	intelhaddata->chmap->kctl->info = had_chmap_ctl_info;
 	intelhaddata->chmap->kctl->get = had_chmap_ctl_get;
 	intelhaddata->chmap->chmap = NULL;
+
+	/* drop the inherited TLV read: it walks chmap without our mutex */
+	intelhaddata->chmap->kctl->tlv.c = NULL;
+	intelhaddata->chmap->kctl->vd[0].access &=
+		~(SNDRV_CTL_ELEM_ACCESS_TLV_READ | SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
+
 	return 0;
 }
 

From: Peter Ujfalusi <[email protected]>

[ Upstream commit f5e1a9a3fddab8421416b68bb132ae9626d07156 ]

had_build_channel_allocation_map() allocates a single struct snd_pcm_chmap_elem via kzalloc() and stores it as intelhaddata->chmap->chmap. struct snd_pcm_chmap.chmap is expected to be a zero-terminated array (see snd_pcm_std_chmaps[]), but had_register_chmap_ctls() never overrides the TLV callback installed by snd_pcm_add_chmap_ctls(), so the generic pcm_chmap_ctl_tlv() from ALSA core is left in place.

pcm_chmap_ctl_tlv() is reachable by any local user via SNDRV_CTL_IOCTL_TLV_READ on the "Playback Channel Map" control and walks the array with "for (map = info->chmap; map->channels; map++)". Since the driver's single element is never terminated, this walks past the allocation. The same pointer is also freed on hot-unplug and rebuilt on hot-plug under intelhaddata->mutex, while the TLV callback runs under card->controls_rwsem without that mutex, so the walk can also race a concurrent free of the array.

Fix this by allocating a second, zeroed element so the array is properly terminated, and by dropping the inherited TLV callback entirely at registration time, since the driver never implements one of its own.

---
 sound/x86/intel_hdmi_audio.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

index 8e2a007311d36..21ee9c9154804 100644
@@ -475,7 +475,8 @@ static void had_build_channel_allocation_map(struct snd_intelhad *intelhaddata)
 	kfree(intelhaddata->chmap->chmap);
 	intelhaddata->chmap->chmap = NULL;
 
-	chmap = kzalloc(sizeof(*chmap), GFP_KERNEL);
+	/* info->chmap must be zero-terminated; allocate a spare terminator entry */
+	chmap = kzalloc_objs(*chmap, 2);
 	if (!chmap)
 		return;
 

@@ -575,6 +576,12 @@ static int had_register_chmap_ctls(struct snd_intelhad *intelhaddata,
 	intelhaddata->chmap->kctl->info = had_chmap_ctl_info;
 	intelhaddata->chmap->kctl->get = had_chmap_ctl_get;
 	intelhaddata->chmap->chmap = NULL;
+
+	/* drop the inherited TLV read: it walks chmap without our mutex */
+	intelhaddata->chmap->kctl->tlv.c = NULL;
+	intelhaddata->chmap->kctl->vd[0].access &=
+		~(SNDRV_CTL_ELEM_ACCESS_TLV_READ | SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK);
+
 	return 0;
 }
 

2.53.0