From 95b2e0361c88753afa030c10698be0a1a5b67650 Mon Sep 17 00:00:00 2001 From: Kyle Zeng Date: Thu, 17 Sep 2026 12:56:43 +0200 Subject: [PATCH] ALSA: seq: Serialize compat port-info ioctls The native sequencer ioctl path serializes handler calls with client->ioctl_mutex, but the translated port-info compat path invokes the same handlers through snd_seq_kernel_client_ctl() without taking that mutex. This lets concurrent compat CREATE_PORT requests pass the port-count check before any request reaches the serialized insertion. The computed integer port index can then exceed the address field range and wrap to an existing index. Subsequent subscriber teardown can resolve the duplicate address to the wrong port and access a freed subscriber. Take ioctl_mutex while dispatching converted port-info requests, matching the native ioctl path. All translated port-info commands share this helper, so their accesses to the client port state are serialized as well. Fixes: b3defb791b26 ("ALSA: seq: Make ioctls race-free") Cc: stable@vger.kernel.org Assisted-by: Codex:gpt-5.6-sol gpt-6-astra Signed-off-by: Kyle Zeng Signed-off-by: Bruno Produit Link: https://patch.msgid.link/20260917105643.90102-1-bruno.produit@trailofbits.com Signed-off-by: Takashi Iwai --- sound/core/seq/seq_compat.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/sound/core/seq/seq_compat.c b/sound/core/seq/seq_compat.c index 22679dca9aae..80110501da6f 100644 --- a/sound/core/seq/seq_compat.c +++ b/sound/core/seq/seq_compat.c @@ -44,7 +44,9 @@ static int snd_seq_call_port_info_ioctl(struct snd_seq_client *client, unsigned return -EFAULT; data->kernel = NULL; - err = snd_seq_kernel_client_ctl(client->number, cmd, data); + scoped_guard(mutex, &client->ioctl_mutex) { + err = snd_seq_kernel_client_ctl(client->number, cmd, data); + } if (err < 0) return err;