Messages in this thread | | | Date | Fri, 29 May 2015 14:36:36 +0200 | Subject | Re: [PATCH v3 1/4] ozwpan: Use proper check to prevent heap overflow | From | Frans Klaver <> |
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Hi,
On Fri, May 29, 2015 at 2:00 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote: > On Fri, May 29, 2015 at 01:06:58PM +0200, Jason A. Donenfeld wrote: >> --- a/drivers/staging/ozwpan/ozusbsvc1.c >> +++ b/drivers/staging/ozwpan/ozusbsvc1.c >> @@ -390,10 +390,15 @@ void oz_usb_rx(struct oz_pd *pd, struct oz_elt *elt) >> case OZ_GET_DESC_RSP: { >> struct oz_get_desc_rsp *body = >> (struct oz_get_desc_rsp *)usb_hdr; >> - int data_len = elt->length - >> - sizeof(struct oz_get_desc_rsp) + 1; >> - u16 offs = le16_to_cpu(get_unaligned(&body->offset)); >> - u16 total_size = >> + u16 offs, total_size; >> + u8 data_len; >> + >> + if (elt->length < sizeof(struct oz_get_desc_rsp) - 1) >> + break; >> + data_len = elt->length - >> + (sizeof(struct oz_get_desc_rsp) - 1); > > Gar... I'm really sorry. I wanted to Ack these and be done but why did > the + 1 change to a - 1? And I had the same question about the other > patch as well.
I would say that it is because part of the expression has been placed inside parentheses:
a - b + 1 == a - (b - 1)
Guess it makes the decision logic slightly more readable.
Frans
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