Messages in this thread |  | | Date | Mon, 13 Apr 2015 17:53:31 +0200 | From | Quentin Casasnovas <> | Subject | Re: [PATCH] cdc-acm: prevent infinite loop when parsing CDC headers. |
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Adding Greg on CC as suggested by Oliver.
On Mon, Apr 13, 2015 at 05:24:04PM +0200, Quentin Casasnovas wrote: > Phil and I found out a problem with commit: > > 7e860a6e ("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: 7e860a6e ("cdc-acm: add sanity checks") > Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com> > Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com> > CC: Oliver Neukum <oneukum@suse.de> > CC: Adam Lee <adam8157@gmail.com> > --- > drivers/usb/class/cdc-acm.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c > index 6836177..1ac4587 100644 > --- a/drivers/usb/class/cdc-acm.c > +++ b/drivers/usb/class/cdc-acm.c > @@ -1133,11 +1133,12 @@ static int acm_probe(struct usb_interface *intf, > } > > while (buflen > 0) { > + if ((elength = buffer[0]) == 0) > + break; > 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 */ > -- > 2.0.5 >
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