From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8D96D2BD030; Wed, 8 Apr 2026 18:47:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775674066; cv=none; b=qE4qe10n9utTW3n5ROyh3NzsXFzbqXNLKvoy25WiSSkTNOZktJuygG0HUOlw7ffo3y1+0M8gh0TeiD+fHRRmRMN7vOgE8gdKWSJiIU4ywIaTnVxHMq9GAPXUGT+DLlFw+QXRFwBLZ/8I1slpq97DnOVzi5povnvk0B+Kr6aZ9c0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775674066; c=relaxed/simple; bh=oT2lfgBoE/2Sm8iJZkNx/VDPIviN2sLhlE6qWeVx6Sk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uRObNsLBCDOLxRy0tMGYTtj1FE52F8/DvxgJjI3ZtvCWHlRFFFJOveMHMDVDAmcvo+7WXJ8AfAq6CNp0CCzCsatfd5+eB2hc8kBzyQwYm7uA2EtHyaDBWrHelWFdAqJWqfaLsfnGqBWofsh6RTISJJrP0ELj+gDbvmSyFjo7vQE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XflAaftn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XflAaftn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 23596C19421; Wed, 8 Apr 2026 18:47:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775674066; bh=oT2lfgBoE/2Sm8iJZkNx/VDPIviN2sLhlE6qWeVx6Sk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XflAaftnop3bbACymX/d/k7VW/Z2JwZyU0K+ylTDXDkjXbRooy61REC8JeswlVe4M ExPoe67sS6xWsOTNt0bHQdZ6lNU2hr8fywGnrnMeP6+BBeflOW5YcRiyFDDxEy6985 9Uz0+tHohdhl3l4rn4nBiH22udCDEMqKfxaseShE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sebastian Urban , stable , Alan Stern Subject: [PATCH 6.12 196/242] usb: gadget: dummy_hcd: fix premature URB completion when ZLP follows partial transfer Date: Wed, 8 Apr 2026 20:03:56 +0200 Message-ID: <20260408175934.419624467@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175927.064985309@linuxfoundation.org> References: <20260408175927.064985309@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: Sebastian Urban commit f50200dd44125e445a6164e88c217472fa79cdbc upstream. When a gadget request is only partially transferred in transfer() because the per-frame bandwidth budget is exhausted, the loop advances to the next queued request. If that next request is a zero-length packet (ZLP), len evaluates to zero and the code takes the unlikely(len == 0) path, which sets is_short = 1. This bypasses the bandwidth guard ("limit < ep->ep.maxpacket && limit < len") that lives in the else branch and would otherwise break out of the loop for non-zero requests. The is_short path then completes the URB before all data from the first request has been transferred. Reproducer (bulk IN, high speed): Device side (FunctionFS with Linux AIO): 1. Queue a 65024-byte write via io_submit (127 * 512, i.e. a multiple of the HS bulk max packet size). 2. Immediately queue a zero-length write (ZLP) via io_submit. Host side: 3. Submit a 65536-byte bulk IN URB. Expected: URB completes with actual_length = 65024. Actual: URB completes with actual_length = 53248, losing 11776 bytes that leak into subsequent URBs. At high speed the per-frame budget is 53248 bytes (512 * 13 * 8). The 65024-byte request exhausts this budget after 53248 bytes, leaving the request incomplete (req->req.actual < req->req.length). Neither the request nor the URB is finished, and rescan is 0, so the loop advances to the ZLP. For the ZLP, dev_len = 0, so len = min(12288, 0) = 0, taking the unlikely(len == 0) path and setting is_short = 1. The is_short handler then sets *status = 0, completing the URB with only 53248 of the expected 65024 bytes. Fix this by breaking out of the loop when the current request has remaining data (req->req.actual < req->req.length). The request resumes on the next timer tick, preserving correct data ordering. Signed-off-by: Sebastian Urban Cc: stable Reviewed-by: Alan Stern Link: https://patch.msgid.link/20260315151045.1155850-1-surban@surban.net Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/udc/dummy_hcd.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/usb/gadget/udc/dummy_hcd.c +++ b/drivers/usb/gadget/udc/dummy_hcd.c @@ -1537,6 +1537,12 @@ top: /* rescan to continue with any other queued i/o */ if (rescan) goto top; + + /* request not fully transferred; stop iterating to + * preserve data ordering across queued requests. + */ + if (req->req.actual < req->req.length) + break; } return sent; }