[PATCH] ALSA: seq: Fix UMP group 16 filtering

[PATCH] ALSA: seq: Fix UMP group 16 filtering

[Cássio Gabriel]

The sequencer UAPI defines group_filter as an unsigned int bitmap.
Bit 0 filters groupless messages and bits 1-16 filter UMP groups 1-16.

The internal snd_seq_client storage is only unsigned short, so bit 16
is truncated when userspace sets the filter. The same truncation affects
the automatic UMP client filter used to avoid delivery to inactive
groups, so events for group 16 cannot be filtered.

Store the internal bitmap as unsigned int and keep both userspace-provided
and automatically generated values limited to the defined UAPI bits.

Fixes: d2b706077792 ("ALSA: seq: Add UMP group filter")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/core/seq/seq_clientmgr.c  | 2 +-
 sound/core/seq/seq_clientmgr.h  | 5 ++++-
 sound/core/seq/seq_ump_client.c | 2 +-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 75a7a2af9d8c..5719637575a9 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1253,7 +1253,7 @@ static int snd_seq_ioctl_set_client_info(struct snd_seq_client *client,
 	if (client->user_pversion >= SNDRV_PROTOCOL_VERSION(1, 0, 3))
 		client->midi_version = client_info->midi_version;
 	memcpy(client->event_filter, client_info->event_filter, 32);
-	client->group_filter = client_info->group_filter;
+	client->group_filter = client_info->group_filter & SND_SEQ_GROUP_FILTER_MASK;
 
 	/* notify the change */
 	snd_seq_system_client_ev_client_change(client->number);
diff --git a/sound/core/seq/seq_clientmgr.h b/sound/core/seq/seq_clientmgr.h
index ece02c58db70..feea8bb7d987 100644
--- a/sound/core/seq/seq_clientmgr.h
+++ b/sound/core/seq/seq_clientmgr.h
@@ -14,6 +14,9 @@
 
 /* client manager */
 
+#define SND_SEQ_GROUP_FILTER_MASK	GENMASK(SNDRV_UMP_MAX_GROUPS, 0)
+#define SND_SEQ_GROUP_FILTER_GROUPS	GENMASK(SNDRV_UMP_MAX_GROUPS, 1)
+
 struct snd_seq_user_client {
 	struct file *file;	/* file struct of client */
 	/* ... */
@@ -40,7 +43,7 @@ struct snd_seq_client {
 	int number;		/* client number */
 	unsigned int filter;	/* filter flags */
 	DECLARE_BITMAP(event_filter, 256);
-	unsigned short group_filter;
+	unsigned int group_filter;
 	snd_use_lock_t use_lock;
 	int event_lost;
 	/* ports */
diff --git a/sound/core/seq/seq_ump_client.c b/sound/core/seq/seq_ump_client.c
index fdc76f23e03f..9079ccfdc866 100644
--- a/sound/core/seq/seq_ump_client.c
+++ b/sound/core/seq/seq_ump_client.c
@@ -369,7 +369,7 @@ static void setup_client_group_filter(struct seq_ump_client *client)
 	cptr = snd_seq_kernel_client_get(client->seq_client);
 	if (!cptr)
 		return;
-	filter = ~(1U << 0); /* always allow groupless messages */
+	filter = SND_SEQ_GROUP_FILTER_GROUPS; /* always allow groupless messages */
 	for (p = 0; p < SNDRV_UMP_MAX_GROUPS; p++) {
 		if (client->ump->groups[p].active)
 			filter &= ~(1U << (p + 1));

---
base-commit: 0d672ef050d4e1c3891c9944f72c85769978bbee
change-id: 20260422-alsa-seq-ump-group16-filter-cd4c31a3066e

Best regards,
--  
Cássio Gabriel <cassiogabrielcontato@gmail.com>

Re: [PATCH] ALSA: seq: Fix UMP group 16 filtering

[Takashi Iwai]

On Wed, 06 May 2026 05:15:48 +0200,
Cássio Gabriel wrote:
> 
> The sequencer UAPI defines group_filter as an unsigned int bitmap.
> Bit 0 filters groupless messages and bits 1-16 filter UMP groups 1-16.
> 
> The internal snd_seq_client storage is only unsigned short, so bit 16
> is truncated when userspace sets the filter. The same truncation affects
> the automatic UMP client filter used to avoid delivery to inactive
> groups, so events for group 16 cannot be filtered.
> 
> Store the internal bitmap as unsigned int and keep both userspace-provided
> and automatically generated values limited to the defined UAPI bits.
> 
> Fixes: d2b706077792 ("ALSA: seq: Add UMP group filter")
> Cc: stable@vger.kernel.org
> Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>

A good catch!  Applied now.


thanks,

Takashi