From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794369684; b=xvqqxoeJzTn56uOEC0eLyRmcNy7hPe2nhJrpAkOwp+RJ2qSMFvrv1SIzLsvcPwEV8czg rOC+DHqp25KYBjEKB8NhURUwSJD0dzuD0gFE9h4kpZ6s85LZXVpBIf/VBoiB6Gvdx1J3+ 5zeBJ0U4vwoNATL00iJ0dbikvmIonBQsPhNVI2gKAUy1gk3/SLCRjLsyjxbhcxGF9+LBA BPmdsBpBXrCBU1NsRMZrmL/qdJIhNmybeXKVX0odezZ9FE3cbLR42I6azbMB/0214T2XO CDDgBCUaibt4OucNuQAcDpl8zWGINBQn6k8ebm92qVThVoZRufSQ9MuoBiZ7mVXkTUQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794369684; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=J07IkmirLsFUQkkNriM2aGVqXZNRX/3/ujBseBrSD+M=; b=N17kYZcwSKko/4tWv+nEfJ+4RYKIgORb2Cmn0ABDsez40xYwk9eJhnflaufzFq6TEXrA 0fFTHrQhFPgnL5HU9gUOQZPlCV5lL6bWd+miCd3zZQmYu64j+rNjMP99USQ4cI0T40Vom /BgdNh7/Iu1VubUbKz2vltLCaCBWETyaB/Hym9R8JX4Fof5Mv1jCNICqudirX7+YzuQzW 3WrmMX/B3vAoGIFt97iFmbXkD2hyqjQJQ6n2V1UcND47UyHrE6RiY1gmUcHomcT2VthFP 2mRhnTUNbopk/F25Og3iqji01w5uBuzQ36QCjPzRQfPiOmbYEa74UCMo59whw4Y3L4w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ccxhw2kV; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44D9B606A320 for ; Wed, 11 Nov 2026 04:01:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ccxhw2kV Received: by smtp.kernel.org (Postfix) with ESMTPSA id 661C91F0089F; Wed, 11 Nov 2026 04:01:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794369683; bh=J07IkmirLsFUQkkNriM2aGVqXZNRX/3/ujBseBrSD+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ccxhw2kVZ9BEtPb17q+2UkpOWUT7kgb30YInrkPUw3JKzmp9YfIh4KjXppdCe5/if nbWd0LHebdBXWIc08BhVItNJVVe1Z0/WURUhbW50+R9PAgPuNx+G0Naz7hN4Vl/VIk PVfyg1561fNtBANtrlcMU9lCBK8+7tAohVXhRGUQymjHmJ7hMsP6nKW6ZyZK8D1/AJ C4lUfpVNQ84cCnNQe81mx1QxiBQlBD040DlM5kYG0eMEf4MR2hqMhHvMHLN0HZa+3c awGem4MVZgsu2XDGXNnw1ExspbaRH+V4H5OIwNeKe2q9X9yu04UCwu/tmxgTOrjsrq tr678mQ8Fqbhg== From: Sasha Levin To: stable@vger.kernel.org Cc: Sinan Turunc , Takashi Iwai , Sasha Levin Subject: [PATCH 5.15.y] ALSA: usb-audio: Bound packet copies by the PCM buffer size Date: Tue, 10 Nov 2026 23:01:22 -0500 Message-ID: <20261111040046.1014701-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107061244-failed-5.15-06be918062ad@kernel.org> References: <20261107061244-failed-5.15-06be918062ad@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Sinan Turunc [ Upstream commit 06be918062adc1a5a76dc346803b136b20bdb5ae ] retire_capture_urb() and prepare_playback_urb() assume that one USB packet never carries more data than the whole ALSA ring buffer. Nothing enforces that: the packet size comes from the device (wMaxPacketSize, and curpacksize == maxpacksize when the class-specific endpoint descriptor sets MaxPacketsOnly), while the PCM hardware constraints only require 64-byte periods, two periods and a period time of one data interval. An 8 kHz mono U8 stream on a 128-byte buffer is legal, and a full-speed device can send 1023-byte packets into it. On the first oversized packet hwptr_done is wrapped once and stays beyond buffer_bytes (895 for 1023 bytes into 128). On the next packet the wrap arithmetic in the copy path computes bytes1 = subs->buffer_bytes - oldptr with oldptr > buffer_bytes, so bytes1 wraps to about 4 GB and memcpy() runs off the end of the URB buffer and of the vmalloc'd DMA buffer: BUG: KASAN: slab-out-of-bounds in retire_capture_urb+0x251/0x870 Read of size 4294966529 at addr ffff88800c1e2800 by task vhci_rx/82 and for playback, where copy_to_urb() has the same shape: BUG: KASAN: vmalloc-out-of-bounds in copy_to_urb.isra.0+0x188/0x430 Read of size 4294966529 at addr ffffc9000004537f by task vhci_rx/79 prepare_playback_urb+0x98a/0x1fc0 Truncate an oversized capture packet to the buffer size, and stop filling a playback URB once it holds a whole buffer. With bytes <= buffer_bytes the single wrap of hwptr_done and the two-part memcpy() in both copy paths stay inside the buffer. A device whose packets do not fit the buffer at all was never going to play correctly anyway. Reproduced on 7.3-rc7 with a USB/IP device (dummy_hcd cannot carry isochronous data) advertising a UAC1 endpoint with MaxPacketsOnly and wMaxPacketSize 1023, and a PCM client using period_size 64, periods 2. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Sinan Turunc Signed-off-by: Takashi Iwai Link: https://patch.msgid.link/20261026223543.620-2-enscrpt@pm.me [ sashal: added the missing ctx->buffer_size check that was already present upstream ] Signed-off-by: Sasha Levin --- sound/usb/pcm.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index 737302cfede8f..2f3fadeeb3a38 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -1228,6 +1228,18 @@ static void retire_capture_urb(struct snd_usb_substream *subs, bytes -= adj; subs->stream_offset_adj -= adj; } + /* + * A packet can be as large as the endpoint's maxpacksize, which + * the device chooses, while the ring buffer can be as small as + * two 64-byte periods. The hwptr_done wrap below handles one + * wrap only, so never take more than one buffer from a packet. + */ + if (unlikely(bytes > subs->buffer_bytes)) { + dev_warn_ratelimited(&subs->dev->dev, + "%u-byte packet exceeds %u-byte buffer, truncating\n", + bytes, subs->buffer_bytes); + bytes = subs->buffer_bytes; + } frames = bytes / stride; if (!subs->txfr_quirk) bytes = frames * stride; @@ -1441,7 +1453,14 @@ static int prepare_playback_urb(struct snd_usb_substream *subs, for (i = 0; i < ctx->packets; i++) { counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, avail); - if (counts < 0) + /* + * Bound by the ring buffer as well as by the URB: + * copy_to_urb() wraps hwptr_done once, so one URB must + * never carry more than the whole buffer. + */ + if (counts < 0 || + (frames + counts) * stride > ctx->buffer_size || + (frames + counts) * stride > subs->buffer_bytes) break; /* set up descriptor */ urb->iso_frame_desc[i].offset = frames * stride; -- 2.53.0