On Thu, Sep 21, 2017 at 03:51:44PM +0200, Andrey Konovalov wrote: > On Thu, Sep 21, 2017 at 10:04 AM, Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Sep 21, 2017 at 09:31:54AM +0200, Greg Kroah-Hartman wrote: > >> On Wed, Sep 20, 2017 at 04:45:08PM +0200, Andrey Konovalov wrote: > >> > Hi! > >> > > >> > I've got the following crash while fuzzing the kernel with syzkaller. > >> > > >> > On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18). > >> > > >> > It looks like cdc_parse_cdc_header() doesn't validate buflen before > >> > accessing buffer[1], buffer[2] and so on. The only check present is > >> > while (buflen > 0). > >> > >> Ugh, you are right, let me go work on a patch, thanks for the report... > > > > Here's a first cut at a fix for this. I think this should solve it, but > > it's early and my coffee has not fully kicked in... > > > > thanks, > > > > greg k-h > > ----------------- > > > > diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c > > index 4c38ea41ae96..028feaf01aa5 100644 > > --- a/drivers/usb/core/message.c > > +++ b/drivers/usb/core/message.c > > @@ -2069,6 +2069,10 @@ int cdc_parse_cdc_header(struct usb_cdc_parsed_header *hdr, > > elength = 1; > > goto next_desc; > > } > > + if ((buflen < elength) || (elength < 2)) { > > Hi Greg, > > I think this should check (elength < 3), since we access both > buffer[1] and buffer[2] after this check. {sigh} yes, you are right, counted this one wrong. With this patch, updated one below, does it fix your crash? thanks, greg k-h diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c index 4c38ea41ae96..028feaf01aa5 100644 --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -2069,6 +2069,10 @@ int cdc_parse_cdc_header(struct usb_cdc_parsed_header *hdr, elength = 1; goto next_desc; } + if ((buflen < elength) || (elength < 3)) { + dev_err(&intf->dev, "invalid descriptor buffer length\n"); + break; + } if (buffer[1] != USB_DT_CS_INTERFACE) { dev_err(&intf->dev, "skipping garbage\n"); goto next_desc; -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html