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 0021842882B; Fri, 7 Aug 2026 15:07:48 +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=1786115270; cv=none; b=sLlKpLINNzIzHhd+NIku7GL0IrsLRIs8RshvVf3ohcfmnBZhI++Zv/izchZnK0NXWqavmeMowYJLdbjlbVGASGYZQvO47/7uJm5XhaCy9MI5VuGYthbuBYWfZGp27fM6TQs/pY/7dUGVnKtZV9CcnrTSrvicqKfwHmYeY38gw20= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786115270; c=relaxed/simple; bh=76Vqflt20/szlldkISE2v2Wn9DPR5kVgC3MCwZw4aGA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VU4b5itKqRzvRnGTUJu0CtW26kQFtvbTIqkneuLzNgZd5Or7cAZOD5Re2YDnsVtsGIujzOq6HDLbiA5BTHRli6BDYS9HiubKE3YBlg8R+Gg07DI+4M+cDsBE8avMtpk+0nQp1mQU8oHmJ7KjJHvxYhDilEob0XPIpj/r2OVtVY4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Yzni90gK; 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="Yzni90gK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D2081F000E9; Fri, 7 Aug 2026 15:07:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786115268; bh=XNMSWFEsnGBYIkEroV7WBcUcX05jwKFdKsOP+owf91k=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Yzni90gK8E2XWrCWLSJN1bX8U+qcIYL9IYvzDg5GhyDjW3JCK6WlI7pe2UMSXroOR Fs5YBLNziyfbmur/hrJ/En/HtjUa3JUGjXVDNY/FDBu8c6+BpDPDesvSurfCxjcZz2 Gh5e08PuDJ6nYxyVoX166rI/CYTQ4dXne9r4Pxnw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Takashi Iwai , Federico Kirschbaum , Baul Lee Subject: [PATCH 6.18 216/396] ALSA: usb-audio: fix OOB write in snd_usbmidi_akai_output() Date: Fri, 7 Aug 2026 16:36:16 +0200 Message-ID: <20260807143428.926746118@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143424.272339768@linuxfoundation.org> References: <20260807143424.272339768@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: Baul Lee commit 0970274613fb463d376211450cab066d34ebfe6a upstream. snd_usbmidi_akai_output() computes its fill-loop bound buf_end = ep->max_transfer - MAX_AKAI_SYSEX_LEN - 1; as a signed int, so a small device-advertised bulk-OUT max_transfer makes buf_end negative. The loop guard then compares the u32 urb->transfer_buffer_length against that negative int: the usual arithmetic conversion turns buf_end into a large unsigned value, so the guard stays true and each iteration keeps appending SysEx framing and payload bytes past the end of the URB transfer buffer, which is only max_transfer bytes long. A USB device that advertises a tiny bulk-OUT endpoint can therefore trigger an attacker-length- and content-controlled heap out-of-bounds write when a process writes to the created /dev/snd/midiC*D* node. Return early when there is no room for even one SysEx, so the loop is never entered with a bound that would wrap. The loop is the last statement of the function, so bailing out is equivalent to it not running. Discovered by XBOW, triaged by Baul Lee Fixes: 4434ade8c933 ("ALSA: usb-audio: add support for Akai MPD16") Suggested-by: Takashi Iwai Reported-by: Federico Kirschbaum Reported-by: Baul Lee Cc: stable@vger.kernel.org Signed-off-by: Baul Lee Link: https://patch.msgid.link/20260726074500.50145-1-baul.lee@xbow.com Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/usb/midi.c | 2 ++ 1 file changed, 2 insertions(+) --- a/sound/usb/midi.c +++ b/sound/usb/midi.c @@ -793,6 +793,8 @@ static void snd_usbmidi_akai_output(stru msg = urb->transfer_buffer + urb->transfer_buffer_length; buf_end = ep->max_transfer - MAX_AKAI_SYSEX_LEN - 1; + if (buf_end <= 0) + return; /* only try adding more data when there's space for at least 1 SysEx */ while (urb->transfer_buffer_length < buf_end) {