efi_loader: efi_variable_parse_signature() returns NULL on error

[Patrick Wildt]

On Thu, May 07, 2020 at 03:53:29PM +0200, Heinrich Schuchardt wrote:
> On 07.05.20 09:15, AKASHI Takahiro wrote:
> > On Thu, May 07, 2020 at 02:13:18AM +0200, Patrick Wildt wrote:
> >> efi_variable_parse_signature() returns NULL on error, so IS_NULL()
> 
> IS_NULL() seems to be a typo. I will replace it by IS_ERR() when merging.

Hi,

Yes, sorry.

> >> is an incorrect check.  The goto err leads to pkcs7_free_message(),
> >> which works fine on a NULL ptr.
> >>
> >> Signed-off-by: Patrick Wildt <patrick at blueri.se>
> >
> > Reviewed-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> 
> Hello Takahiro,
> 
> there is a second instance of the same error:
> 
> lib/efi_loader/efi_variable.c:412:
> 
>         msg = pkcs7_parse_message(ebuf, ebuflen);
>         free(ebuf);
> out:
>         if (IS_ERR(msg))
>                 return NULL;
> 
> Please, send a patch for that one too.
> 
> Best regards
> 
> Heinrich

No, that is ok.  pkcs7_parse_message() returns an ERR_PTR() on failure,
as you saw in my other diff.  That's why IS_ERR(msg) is fine here, and
we can return NULL.

Best regards,
Patrick

> >
> >>
> >> diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> >> index 58f8fae358..c5fe896de2 100644
> >> --- a/lib/efi_loader/efi_variable.c
> >> +++ b/lib/efi_loader/efi_variable.c
> >> @@ -519,9 +519,8 @@ static efi_status_t efi_variable_authenticate(u16 *variable,
> >>  	var_sig = efi_variable_parse_signature(auth->auth_info.cert_data,
> >>  					       auth->auth_info.hdr.dwLength
> >>  						   - sizeof(auth->auth_info));
> >> -	if (IS_ERR(var_sig)) {
> >> +	if (!var_sig) {
> >>  		debug("Parsing variable's signature failed\n");
> >> -		var_sig = NULL;
> >>  		goto err;
> >>  	}
> >>
>