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 3CDC73B42DC; Mon, 17 Aug 2026 14:26:25 +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=1786976786; cv=none; b=Z/WnrTLjyIief6Dr6M+8g7fuA/6IYwrnyatiYaeYaS9EpjM8/d6wm85bsej2fm0Y9iIVYyCVXHeGVbUrw65HC85HDkMowAOn1qhgTgXXg4T290y1lwE/fgg0zMJsWRYPcpd0badqVs3WIsv5C0djGSJTydxH+ua7oQoP9HujZ64= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786976786; c=relaxed/simple; bh=GALs1WfeOTy0isLWgrTr0i1PZYvNDgnUVz8o7+NmtV4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=O9x5TEfSHEg2RnOvUdoRJJJ+dbWegUInw3LmfyV4mmTnIX4GPLbBjbSRPjOXNOtYIZ1gjNkaF6hBweLXGqmqIFZjM+VNqqAncoqzIoj9kIi+ZFFXEpaiLPUq4Y8T1fXJQQXRcjeh1Aa8vzquPRmySTv2+aJxGkRTvJYrKC5JIGM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nSHfEcoV; 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="nSHfEcoV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 972191F000E9; Mon, 17 Aug 2026 14:26:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786976785; bh=uCaVh45dEb3CkXZ0lwqk1a0B35hmv8NE3BIz6E+9uxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nSHfEcoVzWOJQ51h+wSFtwbuC7ZH50EDV+WCucVoxRSS3RpEv1IOoG0Nv0OlUGS9Y cFWhBrf0mkEKD8BkpHUim2FPyUh+J+6wgy0YdkzbfLZE4cJmTnZT+PGf12DfICPAvC rDoQO+QSz7EYeclicPPt+6SSLXE0sAhbWJRVW3qk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Peter Chen , Melbin K Mathew Subject: [PATCH 5.15 064/456] usb: gadget: printer: fix infinite loop in printer_read() Date: Mon, 17 Aug 2026 15:27:34 +0200 Message-ID: <20260817132542.554549629@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132539.792407575@linuxfoundation.org> References: <20260817132539.792407575@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Melbin K Mathew commit c2e819be6a5c7f34344926b4bd7e3dfca58cf48a upstream. printer_read() uses the same variable for the requested copy size and the number of bytes actually copied to user space. copy_to_user() returns the number of bytes not copied, so when it fails to copy anything, the computed copied length becomes zero. In that case len, buf, current_rx_bytes and current_rx_buf are left unchanged. If RX data is available and the user buffer remains unwritable, the read loop can repeat indefinitely. Track the copied length separately and return -EFAULT, or the number of bytes already copied, if an iteration makes no progress. Fixes: b185f01a9ab7 ("usb: gadget: printer: factor out f_printer") Cc: stable Reviewed-by: Peter Chen Signed-off-by: Melbin K Mathew Link: https://patch.msgid.link/20260709205622.55700-1-mlbnkm1@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_printer.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) --- a/drivers/usb/gadget/function/f_printer.c +++ b/drivers/usb/gadget/function/f_printer.c @@ -430,7 +430,7 @@ printer_read(struct file *fd, char __use { struct printer_dev *dev = fd->private_data; unsigned long flags; - size_t size; + size_t size, not_copied, copied; size_t bytes_copied; struct usb_request *req; /* This is a pointer to the current USB rx request. */ @@ -523,10 +523,12 @@ printer_read(struct file *fd, char __use else size = len; - size -= copy_to_user(buf, current_rx_buf, size); - bytes_copied += size; - len -= size; - buf += size; + not_copied = copy_to_user(buf, current_rx_buf, size); + copied = size - not_copied; + + bytes_copied += copied; + len -= copied; + buf += copied; spin_lock_irqsave(&dev->lock, flags); @@ -541,6 +543,17 @@ printer_read(struct file *fd, char __use if (dev->interface < 0) goto out_disabled; + if (!copied) { + dev->current_rx_req = current_rx_req; + dev->current_rx_bytes = current_rx_bytes; + dev->current_rx_buf = current_rx_buf; + spin_unlock_irqrestore(&dev->lock, flags); + mutex_unlock(&dev->lock_printer_io); + return bytes_copied ? bytes_copied : -EFAULT; + } + + size = copied; + /* If we not returning all the data left in this RX request * buffer then adjust the amount of data left in the buffer. * Othewise if we are done with this RX request buffer then