From: Kyle Zeng Date: Fri, 5 Jun 2026 08:02:04 +0000 (-0700) Subject: ALSA: seq: dummy: fix UMP event stack overread X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=2b5ff4db5d7aa5b981d966df02e687f79ad7b311;p=thirdparty%2Fkernel%2Flinux.git ALSA: seq: dummy: fix UMP event stack overread The dummy sequencer port forwards events by copying an incoming struct snd_seq_event into a stack temporary, rewriting source and destination, and dispatching the temporary to subscribers. That legacy event storage is smaller than struct snd_seq_ump_event. When a UMP event reaches the dummy client, the copy leaves the UMP flag set but only provides legacy-sized stack storage. The subscriber delivery path then uses snd_seq_event_packet_size() and copies a UMP-sized packet from that stack object, reading past the end of the temporary. Use the existing union __snd_seq_event storage and copy the packet size reported for the incoming event before rewriting the common routing fields. This preserves the full UMP packet for UMP events while keeping legacy event handling unchanged. Fixes: 32cb23a0f911 ("ALSA: seq: dummy: Allow UMP conversion") Signed-off-by: Kyle Zeng Link: https://patch.msgid.link/20260605080204.32045-1-kylebot@openai.com Signed-off-by: Takashi Iwai --- diff --git a/sound/core/seq/seq_dummy.c b/sound/core/seq/seq_dummy.c index af45f328ae990..8abe80985dadd 100644 --- a/sound/core/seq/seq_dummy.c +++ b/sound/core/seq/seq_dummy.c @@ -9,6 +9,7 @@ #include #include #include "seq_clientmgr.h" +#include "seq_memory.h" #include #include @@ -81,19 +82,21 @@ dummy_input(struct snd_seq_event *ev, int direct, void *private_data, int atomic, int hop) { struct snd_seq_dummy_port *p; - struct snd_seq_event tmpev; + union __snd_seq_event tmpev; + size_t size; p = private_data; if (ev->source.client == SNDRV_SEQ_CLIENT_SYSTEM || ev->type == SNDRV_SEQ_EVENT_KERNEL_ERROR) return 0; /* ignore system messages */ - tmpev = *ev; + size = snd_seq_event_packet_size(ev); + memcpy(&tmpev, ev, size); if (p->duplex) - tmpev.source.port = p->connect; + tmpev.legacy.source.port = p->connect; else - tmpev.source.port = p->port; - tmpev.dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS; - return snd_seq_kernel_client_dispatch(p->client, &tmpev, atomic, hop); + tmpev.legacy.source.port = p->port; + tmpev.legacy.dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS; + return snd_seq_kernel_client_dispatch(p->client, &tmpev.legacy, atomic, hop); } /*