From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2363F46F49E; Tue, 21 Jul 2026 17:58:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784656733; cv=none; b=WdudRk64c5/+ERW6kTMf7IGf2O2xFGv/8CrGvWvnviL59mh+AMqZU+2JpF1kaR7yn5iVqSQzCEBq2V/BYJr5Z5BmzDkLJacjNO8MgUk3bJu5Rl9RaDRQUrBh1qtiP24VhoJ4RBIp06akI5d4wePL6XadtXreInIC+eH+TCuP4jY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784656733; c=relaxed/simple; bh=M41NYwUwpXREeMx6LFWs5jlVm6SMBdHBawAYFIHlTs0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=s8MYmJ2bWMy43kSrRE7ceoNCmbK043+yn8CJTjCf0FdBesPlrrWWCXqMKTvB9t+rxGQsdvEO8Fkh/UDaws3i0lGX/r/aFLlBMO+0C9u8ivWET4XJKCEc+gTOaxq+kRN9Ff3mdxl2Ruhn1ix72vErfWkoNwipHFxOYMcdYR8At1E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=PyyaaUD/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="PyyaaUD/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 421411F00A3A; Tue, 21 Jul 2026 17:58:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784656731; bh=8noXbNhMyUF6OpF3Zvrx/mxCieVjaxKvCVS11Jwi6NY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PyyaaUD/TgP+zDWzRkLlKwfZBgydv1QRZhVc+94PKGIKuBTqVxc8uPmN0OBdrvsRY Ou0t0TErzuN8NCGEmvmWlp5UDp/+tefGBTgOeEB2531TfUbXz5w8fJU29oxaRSw/2d BFH8ZcSqPVjBuDkxatXtKIP1Msz+BTDkHH0YuycI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, HanQuan , Takashi Iwai , Sasha Levin Subject: [PATCH 6.18 0497/1611] ALSA: seq: Fix kernel heap address leak in bounce_error_event() Date: Tue, 21 Jul 2026 17:10:13 +0200 Message-ID: <20260721152526.522130669@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: HanQuan [ Upstream commit efc86691e4d8083d9e380ea95042c2cf679f65fd ] The comment above bounce_error_event() documents that user clients should receive SNDRV_SEQ_EVENT_BOUNCE with the original event embedded as variable-length data, while kernel clients should receive SNDRV_SEQ_EVENT_KERNEL_ERROR with a quoted kernel pointer. However, the implementation unconditionally uses SNDRV_SEQ_EVENT_KERNEL_ERROR with data.quote.event set to the raw struct snd_seq_event pointer for all clients. When a bounce error event is delivered to a USER_CLIENT via snd_seq_read(), the kernel heap address in data.quote.event is exposed to userspace through copy_to_user() in the fixed-length branch. This is a distinct leak path from the one addressed by commit 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read"), which sanitizes data.ext.ptr in the variable-length branch of snd_seq_read(). The bounce_error_event() leak uses fixed-length events that take the else branch where no sanitization occurs. Differentiate the bounce event by client type. For USER_CLIENT, send SNDRV_SEQ_EVENT_BOUNCE with SNDRV_SEQ_EVENT_LENGTH_VARIABLE and data.ext pointing to the original event. The variable-length path in snd_seq_event_dup() copies the event data into chained cells, and snd_seq_expand_var_event() copies only the content -- never the pointer -- to userspace. For KERNEL_CLIENT, keep the existing SNDRV_SEQ_EVENT_KERNEL_ERROR behavior with the quoted pointer. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: HanQuan Link: https://patch.msgid.link/20260612103222.2528305-1-eilaimemedsnaimel@gmail.com Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/core/seq/seq_clientmgr.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index b8b04fc79f489c..0c31b19dd948ba 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -538,16 +538,38 @@ static int bounce_error_event(struct snd_seq_client *client, /* set up quoted error */ memset(&bounce_ev, 0, sizeof(bounce_ev)); - bounce_ev.type = SNDRV_SEQ_EVENT_KERNEL_ERROR; - bounce_ev.flags = SNDRV_SEQ_EVENT_LENGTH_FIXED; + + if (client->type == USER_CLIENT) { + /* + * For user clients, send SNDRV_SEQ_EVENT_BOUNCE with the + * original event embedded as variable-length data. This + * avoids exposing data.quote.event (a kernel pointer) to + * userspace. The variable-length path in snd_seq_event_dup() + * copies the event data from data.ext.ptr into chained cells, + * and snd_seq_expand_var_event() copies only the data content + * -- never the pointer -- to userspace. + */ + bounce_ev.type = SNDRV_SEQ_EVENT_BOUNCE; + bounce_ev.flags = SNDRV_SEQ_EVENT_LENGTH_VARIABLE; + bounce_ev.data.ext.len = sizeof(struct snd_seq_event); + bounce_ev.data.ext.ptr = (char *)event; + } else { + /* + * For kernel clients, quote the event pointer directly. + * Kernel consumers can safely dereference the pointer. + */ + bounce_ev.type = SNDRV_SEQ_EVENT_KERNEL_ERROR; + bounce_ev.flags = SNDRV_SEQ_EVENT_LENGTH_FIXED; + bounce_ev.data.quote.origin = event->dest; + bounce_ev.data.quote.event = event; + bounce_ev.data.quote.value = -err; /* use positive value */ + } + bounce_ev.queue = SNDRV_SEQ_QUEUE_DIRECT; bounce_ev.source.client = SNDRV_SEQ_CLIENT_SYSTEM; bounce_ev.source.port = SNDRV_SEQ_PORT_SYSTEM_ANNOUNCE; bounce_ev.dest.client = client->number; bounce_ev.dest.port = event->source.port; - bounce_ev.data.quote.origin = event->dest; - bounce_ev.data.quote.event = event; - bounce_ev.data.quote.value = -err; /* use positive value */ result = snd_seq_deliver_single_event(NULL, &bounce_ev, atomic, hop + 1); if (result < 0) { client->event_lost++; -- 2.53.0