On Wed, Jul 04, 2018 at 01:59:14PM +0200, Julia Lawall wrote:
>
>
> On Wed, 4 Jul 2018, Dan Carpenter wrote:
>
> > We accidentally removed the check for negative returns without
> > considering the issue of type promotion. The "if_version_length"
> > variable is type size_t so if __mei_cl_recv() returns a negative then
> > "bytes_recv" is type promoted to a high positive value and treated as
> > success.
> >
> > Fixes: 582ab27a063a ("mei: bus: fix received data size check in NFC fixup")
> > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> >
> > diff --git a/drivers/misc/mei/bus-fixup.c b/drivers/misc/mei/bus-fixup.c
> > index 0208c4b027c5..fa0236a5e59a 100644
> > --- a/drivers/misc/mei/bus-fixup.c
> > +++ b/drivers/misc/mei/bus-fixup.c
> > @@ -267,7 +267,7 @@ static int mei_nfc_if_version(struct mei_cl *cl,
> >
> > ret = 0;
> > bytes_recv = __mei_cl_recv(cl, (u8 *)reply, if_version_length, 0);
> > - if (bytes_recv < if_version_length) {
> > + if (bytes_recv < 0 || bytes_recv < if_version_length) {
>
> Is this preferred to adding an int cast?
I don't think it matters. I kind of like explicitly testing for
negative but maybe later people will just remove the check like we did
here? You could do it a bunch of different ways:
1: if (ret < 0 || ret < ARRAY_SIZE(xxx))
2: if (ret < (int)ARRAY_SIZE(xxx))
3: if (ret != ARRAY_SIZE(xxx))
They're all equivalent. I guess I don't like casting too much. My
first approach to fixing this was just to declare if_version_length as
an int, but then I saw that originally there was a "bytes_recv < 0"
check and decided to go that way instead.
regards,
dan carpenter
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