From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: usb/misc/ims-pcu: slab-out-of-bounds in ims_pcu_parse_cdc_data Date: Sat, 7 Oct 2017 11:14:33 -0700 Message-ID: <20171007181433.GA14355@dtor-ws> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pg0-f68.google.com ([74.125.83.68]:37238 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbdJGSOh (ORCPT ); Sat, 7 Oct 2017 14:14:37 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Andrey Konovalov Cc: Johan Hovold , Arvind Yadav , linux-input@vger.kernel.org, LKML , Dmitry Vyukov , Kostya Serebryany , syzkaller On Thu, Sep 28, 2017 at 01:35:51PM +0200, Andrey Konovalov wrote: > Hi! > > I've got the following report while fuzzing the kernel with syzkaller. > > On commit dc972a67cc54585bd83ad811c4e9b6ab3dcd427e (4.14-rc2+). > > There's no check that the length of intf->altsetting->extra is big > enough to hold usb_cdc_union_desc struct. Can you please tell me if the following works for you? Thanks! -- Dmitry Input: ims-psu - check if CDC union descriptor is sane From: Dmitry Torokhov Before trying to use CDC union descriptor, try to validate whether that it is sane by checking that intf->altsetting->extra is big enough and that descriptor bLength is not too big and not too small. Reported-by: Andrey Konovalov Signed-off-by: Dmitry Torokhov --- drivers/input/misc/ims-pcu.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c index 6bf82ea8c918..ae473123583b 100644 --- a/drivers/input/misc/ims-pcu.c +++ b/drivers/input/misc/ims-pcu.c @@ -1635,13 +1635,25 @@ ims_pcu_get_cdc_union_desc(struct usb_interface *intf) return NULL; } - while (buflen > 0) { + while (buflen >= sizeof(*union_desc)) { union_desc = (struct usb_cdc_union_desc *)buf; + if (union_desc->bLength > buflen) { + dev_err(&intf->dev, "Too large descriptor\n"); + return NULL; + } + if (union_desc->bDescriptorType == USB_DT_CS_INTERFACE && union_desc->bDescriptorSubType == USB_CDC_UNION_TYPE) { dev_dbg(&intf->dev, "Found union header\n"); - return union_desc; + + if (union_desc->bLength >= sizeof(*union_desc)) + return union_desc; + + dev_err(&intf->dev, + "Union descriptor to short (%d vs %zd\n)", + union_desc->bLength, sizeof(*union_desc)); + return NULL; } buflen -= union_desc->bLength;