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 4DB4A3A4505; Thu, 30 Jul 2026 15:02:13 +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=1785423734; cv=none; b=HStOPkNJfAPPEqcb8NWXAhZum+YkFZNmfyX8rcADuOXmeAEDGIgl7INsshKox9yHR8xBwre48uS0UH9fFqnEU9/H86MEfGNMobDuRnky12mVbuW8XUb/LaOsArevjGBR/9QYJLh6cR9Ls40FaujP6TnD3/MJ5bz7QBBpSxzHutg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423734; c=relaxed/simple; bh=5ps+wCAgyk/t62Z27BI6YrrZgDRE0HRVxuzn3u/kQ9E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DNHKjqSDhObt5OrpUfESYY3tJuMnEi9YS987sMUaPcXiCaIkooAZUcJkjP3nND6zDLYIgyuJaz43U9iMqokVBVfxBMyOhtd2S19XIhly2tqcCO6xjE3uuYLRhc5nQefOkje/s95vZ5LLyPYaPn5Wcqab9oEnMWcre0g+pBO0b0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=oVVhQut1; 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="oVVhQut1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2F821F000E9; Thu, 30 Jul 2026 15:02:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785423733; bh=V+Znt8nBO/jRr5RcFfgU6nPHCiLMR+d8d6dP+OtEPi4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=oVVhQut1ThhGlCHl6BWoOoXoR7gs45RASWm3yCcstGTLzCNA/Rmv6SdOBW+2cWp91 Mnhg0IXE8yv9FvP9gPGWJukz3c6hU+7MJgzKuKwRK7ZxZi6FsLuC6xzwy+lLD2rcpT Eph8Z/AmWe4tUeorteIPo9ZSh/3flr1mIOIKSCis= 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 6.18 147/675] usb: gadget: printer: fix infinite loop in printer_read() Date: Thu, 30 Jul 2026 16:07:57 +0200 Message-ID: <20260730141448.262498525@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@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: 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 @@ -431,7 +431,7 @@ 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. */ @@ -524,10 +524,12 @@ 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); @@ -542,6 +544,17 @@ 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