Messages in this thread Patch in this message | | | Date | Sat, 7 Oct 2017 11:14:33 -0700 | From | Dmitry Torokhov <> | Subject | Re: usb/misc/ims-pcu: slab-out-of-bounds in ims_pcu_parse_cdc_data |
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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 <dmitry.torokhov@gmail.com>
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 <andreyknvl@google.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> --- 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;
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