Messages in this thread | | | Date | Tue, 14 Apr 2015 14:01:57 +0300 | From | Sergei Shtylyov <> | Subject | Re: [PATCH] cdc-acm: prevent infinite loop when parsing CDC headers. |
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Hello.
On 4/13/2015 7:20 PM, Sergei Shtylyov 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")
> 12-digit SHA1 hash is required here.
>> 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)
> Please run your patches thru scripts/checkpatch.pl. Assignments in the > *if* operator are not allowed.
s/operator/statement/, of course. :-)
> [...]
WBR, Sergei
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