Re: [PATCH] efi_loader: Set variable attributes when EFI_BUFFER_TOO_SMALL is returned

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

On Wed, Mar 16, 2022 at 02:40:20PM +0100, Heinrich Schuchardt wrote:
> On 3/16/22 13:55, Ilias Apalodimas wrote:
> > Starting UEFI Spec 2.8 we must fill in the variable attributes when
> > GetVariable() returns EFI_BUFFER_TOO_SMALL and Attributes is non-NULL.
> > 
> > This code was written with 2.7 in mind so let's move the code around a
> > bit and fill in the attributes EFI_BUFFER_TOO_SMALL is returned
> 
> In the UEFI spec changelog:
> 
> 1954 set (*Attributes) when GetVariable() returns EFI_BUFFER_TOO_SMALL
> and Attributes is non-NULL
> 
> In efi_get_variable_mem() this already works correctly.
> 
> > 
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> > ---
> >   lib/efi_loader/efi_variable_tee.c | 27 ++++++++++++++++++---------
> >   1 file changed, 18 insertions(+), 9 deletions(-)
> > 
> > diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
> > index 58931c4efd74..33c7dfc53d14 100644
> > --- a/lib/efi_loader/efi_variable_tee.c
> > +++ b/lib/efi_loader/efi_variable_tee.c
> > @@ -408,22 +408,31 @@ efi_status_t efi_get_variable_int(const u16 *variable_name,
> >   	/* Communicate */
> >   	ret = mm_communicate(comm_buf, payload_size);
> >   	if (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL) {
> 
> You could make the code easier to read with:
> 
> if (ret != EFI_SUCCESS && ret != EFI_BUFFER_TOO_SMALL)
> 	goto out;
> 

Sure

> > +		int tmp;
> >   		/* Update with reported data size for trimmed case */
> >   		*data_size = var_acc->data_size;
> > +		/*
> > +		 * UEFI > 2.7 needs the attributes set even if the buffer is
> > +		 * smaller
> > +		 */
> > +		tmp = get_property_int(variable_name, name_size, vendor,
> > +				       &var_property);
> 
> Why call get_property_int() if (!attributes)?
> You don't use the data in this case.
> 

Good point.  I just moved the code around, but i'll fix that along the way

Thanks
/Ilias
> Best regards
> 
> Heinrich
> 
> > +		if (tmp != EFI_SUCCESS) {
> > +			ret = tmp;
> > +			goto out;
> > +		}
> > +
> > +		if (attributes) {
> > +			*attributes = var_acc->attr;
> > +			if (var_property.property &
> > +			    VAR_CHECK_VARIABLE_PROPERTY_READ_ONLY)
> > +				*attributes |= EFI_VARIABLE_READ_ONLY;
> > +		}
> >   	}
> > -	if (ret != EFI_SUCCESS)
> > -		goto out;
> > 
> > -	ret = get_property_int(variable_name, name_size, vendor, &var_property);
> >   	if (ret != EFI_SUCCESS)
> >   		goto out;
> > 
> > -	if (attributes) {
> > -		*attributes = var_acc->attr;
> > -		if (var_property.property & VAR_CHECK_VARIABLE_PROPERTY_READ_ONLY)
> > -			*attributes |= EFI_VARIABLE_READ_ONLY;
> > -	}
> > -
> >   	if (data)
> >   		memcpy(data, (u8 *)var_acc->name + var_acc->name_size,
> >   		       var_acc->data_size);
>