The struct describes a bounce payload of an error code followed by the
original event and its external data.  No kernel has ever sent that.
Before commit efc86691e4d8 ("ALSA: seq: Fix kernel heap address leak in
bounce_error_event()") the kernel emitted no SNDRV_SEQ_EVENT_BOUNCE at
all, and since then it sends the event record alone.

Nothing has ever read it either.  Its only accessor,
snd_seq_event_bounce_ext_data(), has had no caller for the whole git
history, and it did not even compile until commit c7e0b5bf9fff ("[ALSA]
Remove xxx_t typedefs: Sequencer") incidentally repaired the type name
it referred to, three years after the git import.  Drop the accessor
along with the struct.

This removes a definition from a UAPI header.  Since no kernel ever
produced the layout, nothing can have parsed it, but a program that
merely names the type will need to stop.

Suggested-by: Takashi Iwai <tiwai@suse.de>
Assisted-by: Claude:claude-opus-5
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
---
 include/sound/asequencer.h      |  3 ---
 include/uapi/sound/asequencer.h | 10 ----------
 sound/core/seq/seq_clientmgr.c  |  5 ++---
 3 files changed, 2 insertions(+), 16 deletions(-)

diff --git a/include/sound/asequencer.h b/include/sound/asequencer.h
index ddbb6bf801bb..efad366736a4 100644
--- a/include/sound/asequencer.h
+++ b/include/sound/asequencer.h
@@ -11,9 +11,6 @@
 #include <sound/asound.h>
 #include <uapi/sound/asequencer.h>
 
-/* helper macro */
-#define snd_seq_event_bounce_ext_data(ev) ((void*)((char *)(ev)->data.ext.ptr + sizeof(struct snd_seq_event_bounce)))
-
 /*
  * type check macros
  */
diff --git a/include/uapi/sound/asequencer.h b/include/uapi/sound/asequencer.h
index a5c41f771e05..3deba3965ca5 100644
--- a/include/uapi/sound/asequencer.h
+++ b/include/uapi/sound/asequencer.h
@@ -308,16 +308,6 @@ struct snd_seq_ump_event {
 	};
 };
 
-/*
- * bounce event - stored as variable size data
- */
-struct snd_seq_event_bounce {
-	int err;
-	struct snd_seq_event event;
-	/* external data follows here. */
-};
-
-
 	/* system information */
 struct snd_seq_system_info {
 	int queues;			/* maximum queues count */
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 11fa7e825819..5b86e75c2658 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -530,9 +530,8 @@ static struct snd_seq_client *get_event_dest_client(struct snd_seq_event *event)
  * Return the error event.
  *
  * If the receiver client is a user client, the original event is
- * encapsulated in SNDRV_SEQ_EVENT_BOUNCE as variable length event.  If
- * the original event is also variable length, the external data is
- * copied after the event record. 
+ * encapsulated in SNDRV_SEQ_EVENT_BOUNCE as variable length event.  The
+ * external data of a variable length event is not copied along.
  * If the receiver client is a kernel client, the original event is
  * quoted in SNDRV_SEQ_EVENT_KERNEL_ERROR, since this requires no extra
  * kmalloc.
-- 
2.43.0

On Wed, 12 Aug 2026 16:15:06 +0200,
HyeongJun An wrote:
> 
> The struct describes a bounce payload of an error code followed by the
> original event and its external data.  No kernel has ever sent that.
> Before commit efc86691e4d8 ("ALSA: seq: Fix kernel heap address leak in
> bounce_error_event()") the kernel emitted no SNDRV_SEQ_EVENT_BOUNCE at
> all, and since then it sends the event record alone.
> 
> Nothing has ever read it either.  Its only accessor,
> snd_seq_event_bounce_ext_data(), has had no caller for the whole git
> history, and it did not even compile until commit c7e0b5bf9fff ("[ALSA]
> Remove xxx_t typedefs: Sequencer") incidentally repaired the type name
> it referred to, three years after the git import.  Drop the accessor
> along with the struct.
> 
> This removes a definition from a UAPI header.  Since no kernel ever
> produced the layout, nothing can have parsed it, but a program that
> merely names the type will need to stop.
> 
> Suggested-by: Takashi Iwai <tiwai@suse.de>
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: HyeongJun An <sammiee5311@gmail.com>

Applied to for-next branch now.  Thanks.


Takashi