[U-Boot] [PATCH] Loop block device for sandbox

Marek Vasut
2012-08-31T16:02:22Z

Dear Pavel Herrmann,

> On Friday 31 of August 2012 14:57:41 Marek Vasut wrote:
> > > > > > > > > +lbaint_t sata_read(int dev, lbaint_t start, lbaint_t
> > > > > > > > > blkcnt, void *buffer)
> > > > > > > > > +{
> > > > > > > > > + block_dev_desc_t *pdev = &(sata_dev_desc[dev]);
> > > > > > > > > + int fd = (long) pdev->priv;
> > > > > > > >
> > > > > > > > If pdev is NULL, this will crash
> > > > > > >
> > > > > > > well, it isn't, at least not from the command - thats why you
> > > > > > > define the number of ports in advance, you get "dev" already
> > > > > > > range-checked
> > > > > >
> > > > > > Range check is fine, but will pdev be inited? It's a pointer from
> > > > > > some array.
> > > > >
> > > > > init_sata is called first, so pdev is inited (see cmd_sata.c)
> > > >
> > > > Unless it fails. Then what ?
> > >
> > > the only way init can "fail" is if it gets a wrong device number (which
> > > should not happen), or if it cannot open the file, in which case it
> > > still sets pdev as -1.
> >
> > If pdev is -1, then this explodes for certain, on unaligned access and on
> > wrong ptr deref.
>
> again, no
>
> there is no pointer in this, pdev->priv is actually an int stored as void*,
> pdev itself is pointer to a global array.
> which one does explode in your case?

pdev, but given that the pointer is inited, I see the issue at hand now.

> > > > > > > > > + memcpy(pdev->product, filenames[dev], namelen);
> > > > > > > > > + pdev->product[20] = 0;
> > > > > > > > > +
> > > > > > > > > + if (fd != -1) {
> > > > > > > >
> > > > > > > > And if "fd" is -1 ?
> > > > > > >
> > > > > > > then all defaults to an invalid device, because you failed to
> > > > > > > open the file, for whatever the reason.
> > > > > >
> > > > > > At least the printf below will choke, since pdev->lba is uninited
> > > > >
> > > > > not the case. sata_dev_desc is inited in cmd_sata.c, and therefore
> > > > > by not doing anything we get an empty device
> > > >
> > > > I see ... shall we also move all these memcpy() calls in to if (fd !=
> > > > -1)
> > > > then?
> > >
> > > I'd like to know that the device is a loopback, and what filename, not
> > > just
> > > that it failed to init
> >
> > But are such data used somewhere further down the road?
>
> yes, "sata info" for example

And how does it determine that the init failed?

I think we're almost clear on these things.

> Pavel Herrmann

Best regards,
Marek Vasut