On Fri, 2013-03-15 at 08:57 +0000, David Woodhouse wrote:
> On Fri, 2013-03-15 at 11:29 +0300, Dan Carpenter wrote:
> > Hello Matthew Garrett,
> >
> > The patch dd5fc854de5f: "EFI: Stash ROMs if they're not in the PCI
> > BAR" from Dec 5, 2012, leads to the following warning:
> > "arch/x86/boot/compressed/eboot.c:290 setup_efi_pci()
> > error: potentially dereferencing uninitialized 'pci_handle'."
> >
> > 254 static efi_status_t setup_efi_pci(struct boot_params *params)
> > 255 {
> > 256 efi_pci_io_protocol *pci;
> > 257 efi_status_t status;
> > 258 void **pci_handle;
> > 259 efi_guid_t pci_proto = EFI_PCI_IO_PROTOCOL_GUID;
> > 260 unsigned long nr_pci, size = 0;
> > 261 int i;
> > 262 struct setup_data *data;
> > 263
> > 264 data = (struct setup_data *)(unsigned long)params->hdr.setup_data;
> > 265
> > 266 while (data && data->next)
> > 267 data = (struct setup_data *)(unsigned long)data->next;
> > 268
> > 269 status = efi_call_phys5(sys_table->boottime->locate_handle,
> > 270 EFI_LOCATE_BY_PROTOCOL, &pci_proto,
> > 271 NULL, &size, pci_handle);
> > ^^^^^^^^^^
> > This hasn't been initialized yet.
>
> True. It probably doesn't *matter* because the size is zero so the
> firmware is just going to ignore the pointer anyway. Although in that
> case I wonder why we couldn't have just passed NULL. Perhaps we expected
> that some firmware might do some validation on the pointer before
> getting to the size check?
I doubt that the firmware checks the validity of pci_handle when size is
zero, and I agree it's worth passing NULL to silence the warning (which
is also more explicit that just initialising pci_handle), unless Matthew
knows of a reason we shouldn't do that?
--
Matt Fleming, Intel Open Source Technology Center
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