Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932507AbbFPIyu (ORCPT ); Tue, 16 Jun 2015 04:54:50 -0400 Received: from mail.kernel.org ([198.145.29.136]:57425 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756677AbbFPIu2 (ORCPT ); Tue, 16 Jun 2015 04:50:28 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Quentin Casasnovas , Phil Turnbull , Sergei Shtylyov , Oliver Neukum , Adam Lee , Greg Kroah-Hartman , Zefan Li Subject: [PATCH 3.4 168/172] cdc-acm: prevent infinite loop when parsing CDC headers. Date: Tue, 16 Jun 2015 16:37:02 +0800 Message-Id: <1434443826-4929-168-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434443587-4599-1-git-send-email-lizf@kernel.org> References: <1434443587-4599-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2222 Lines: 66 From: Quentin Casasnovas 3.4.108-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e upstream. Phil and I found out a problem with commit: 7e860a6e7aa6 ("cdc-acm: add sanity checks") It added some sanity checks to ignore potential garbage in CDC headers but also introduced a potential infinite loop. This can happen at the first loop iteration (elength = 0 in that case) if the description isn't a DT_CS_INTERFACE or later if 'buffer[0]' is zero. It should also be noted that the wrong length was being added to 'buffer' in case 'buffer[1]' was not a DT_CS_INTERFACE descriptor, since elength was assigned after that check in the loop. A specially crafted USB device could be used to trigger this infinite loop. Fixes: 7e860a6e7aa6 ("cdc-acm: add sanity checks") Signed-off-by: Phil Turnbull Signed-off-by: Quentin Casasnovas CC: Sergei Shtylyov CC: Oliver Neukum CC: Adam Lee Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zefan Li --- drivers/usb/class/cdc-acm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 57877a9..25bc1d6 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1044,11 +1044,16 @@ static int acm_probe(struct usb_interface *intf, } while (buflen > 0) { + elength = buffer[0]; + if (!elength) { + dev_err(&intf->dev, "skipping garbage byte\n"); + elength = 1; + goto next_desc; + } if (buffer[1] != USB_DT_CS_INTERFACE) { dev_err(&intf->dev, "skipping garbage\n"); goto next_desc; } - elength = buffer[0]; switch (buffer[2]) { case USB_CDC_UNION_TYPE: /* we've found it */ -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/