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 8D6603E5EC0; Mon, 17 Aug 2026 14:47:10 +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=1786978031; cv=none; b=jOdnJJySnthSdJskcImQ4nNsYHHxoOez1R6s1NEiFYM9L/6i4FE9uupYW1IWG1QkK53EwCDYbSwhMJFBbpIA1Ef6MAe1CJW/W/1VgdFBM6AB4i/hLLQ26AVeoi/PmFbBXeOICVAA1xvTtWWOy1psZVh4PtrDlHmoMAXftlL9dDY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786978031; c=relaxed/simple; bh=rNv3nDCTPuIbUV1c0ZtElBJQJjCyPzd4vDKdRyDD73U=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=h0ncjLXbh3C/nFllI6GQO7Ppvbr44phgGAIC+dPUlzYS7g3MBkQ7NTWFmc0HYy3Qb3ilorE+9DMyAedD7yBk1GjLch9XVn5V9X37mIWeCKCzqeiwxnqFxPJGdJBiLrhYQiewolB5VJU2+EKrSwWqSbS+6Ql+hkAav6+0h/TLxx8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JSD1pee9; 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="JSD1pee9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7F9E1F00A3A; Mon, 17 Aug 2026 14:47:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786978030; bh=PoVOGWCtbBv+E/lr07UGZ0AwS8dAKOjb/8HqhAQQIp8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JSD1pee9TpD9t7xgqn+f9o+dMiDELoPhbjzgSS8oBsMFWlbyH4H7bLd6DvMp8Cio3 Q9PIUL1MUlpkbW5U3Qv6785vwCihEw7O/4gvI5sviGNmYWatamZoJLStXxYEPkx4nS zhG3xQm/mhp40X+e8TtM56esIDhSh9XpRhpQfPmc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Federico Kirschbaum , Baul Lee , Takashi Iwai Subject: [PATCH 6.12 075/181] ALSA: usb-audio: fix OOB write on Type II inbound URBs Date: Mon, 17 Aug 2026 15:32:49 +0200 Message-ID: <20260817132538.400596221@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132535.394764707@linuxfoundation.org> References: <20260817132535.394764707@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Baul Lee commit 69ee44e1a23be62318189dc4b37fa4ad94053269 upstream. data_ep_set_params() sizes each URB transfer buffer before it adds the Format Type II transfer delimiter: u->packets = urb_packs; u->buffer_size = maxsize * u->packets; if (fmt->fmt_type == UAC_FORMAT_TYPE_II) u->packets++; /* for transfer delimiter */ u->urb = usb_alloc_urb(u->packets, GFP_KERNEL); buffer_size is computed from the pre-increment packet count and never recomputed, so for a Type II endpoint the buffer is one packet short of the packet count the URB is built with. prepare_inbound_urb() then lays out one iso frame per packet and never consults buffer_size: offs = 0; for (i = 0; i < urb_ctx->packets; i++) { urb->iso_frame_desc[i].offset = offs; urb->iso_frame_desc[i].length = ep->curpacksize; offs += ep->curpacksize; } urb->transfer_buffer_length = offs; urb->number_of_packets = urb_ctx->packets; The last descriptor therefore points one packet past the end of the transfer buffer, where the host controller writes device data on every inbound transfer. prepare_silent_urb() and prepare_playback_urb() bound their fill loops by ctx->buffer_size, so only capture is affected. fmt_type comes from the device's audio streaming descriptors, so any device advertising a Type II capture format hits this once userspace sets hw_params on the stream. KASAN on 7.2.0-rc5 (arm64) with a dummy_hcd/raw-gadget device, one report per inbound transfer: BUG: KASAN: slab-out-of-bounds in dummy_timer Write of size 64 at addr ffff0000186171c0 by task cons02/166 __asan_memcpy dummy_timer hrtimer_run_softirq Allocated by task 166: usb_alloc_coherent snd_usb_endpoint_set_params The buggy address is located 0 bytes to the right of allocated 64-byte region [ffff000018617180, ffff0000186171c0) Compute buffer_size after the delimiter packet has been accounted for, and bound the fill loop by buffer_size, as prepare_silent_urb() already does on the outbound side. This grows every Type II URB allocation by one maxsize packet. Discovered by XBOW, triaged by Baul Lee Fixes: 8fdff6a319e7 ("ALSA: snd-usb: implement new endpoint streaming model") Reported-by: Federico Kirschbaum Reported-by: Baul Lee Cc: stable@vger.kernel.org Signed-off-by: Baul Lee Link: https://patch.msgid.link/20260805013441.38245-1-baul.lee@xbow.com Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/usb/endpoint.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -388,13 +388,15 @@ static int prepare_inbound_urb(struct sn case SND_USB_ENDPOINT_TYPE_DATA: offs = 0; for (i = 0; i < urb_ctx->packets; i++) { + if (offs + ep->curpacksize > urb_ctx->buffer_size) + break; urb->iso_frame_desc[i].offset = offs; urb->iso_frame_desc[i].length = ep->curpacksize; offs += ep->curpacksize; } urb->transfer_buffer_length = offs; - urb->number_of_packets = urb_ctx->packets; + urb->number_of_packets = i; break; case SND_USB_ENDPOINT_TYPE_SYNC: @@ -1263,10 +1265,10 @@ static int data_ep_set_params(struct snd u->index = i; u->ep = ep; u->packets = urb_packs; - u->buffer_size = maxsize * u->packets; if (fmt->fmt_type == UAC_FORMAT_TYPE_II) u->packets++; /* for transfer delimiter */ + u->buffer_size = maxsize * u->packets; u->urb = usb_alloc_urb(u->packets, GFP_KERNEL); if (!u->urb) goto out_of_memory;