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@xxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
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;
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
