efi_loader: pkcs7_parse_message() returns error pointer

[Heinrich Schuchardt]

On 07.05.20 02:17, Patrick Wildt wrote:
> Since pkcs7_parse_message() returns an error pointer, we must not
> check for NULL.  We have to explicitly set msg to NULL in the error
> case, otherwise the call to pkcs7_free_message() on the goto err
> path will assume it's a valid object.
>
> Signed-off-by: Patrick Wildt <patrick at blueri.se>
>
> diff --git a/lib/efi_loader/efi_image_loader.c b/lib/efi_loader/efi_image_loader.c
> index 5a9a6424cc..43a53d3dd1 100644
> --- a/lib/efi_loader/efi_image_loader.c
> +++ b/lib/efi_loader/efi_image_loader.c
> @@ -538,8 +538,9 @@ static bool efi_image_authenticate(void *efi, size_t efi_size)
>  		}
>  		msg = pkcs7_parse_message((void *)wincert + sizeof(*wincert),
>  					  wincert->dwLength - sizeof(*wincert));
> -		if (!msg) {
> +		if (IS_ERR(msg)) {

Compiling with sandbox_defconfig results in:

lib/efi_loader/efi_image_loader.c: In function ‘efi_image_authenticate’:
lib/efi_loader/efi_image_loader.c:541:7: warning: implicit declaration
of function ‘IS_ERR’ [-Wimplicit-function-declaration]
  541 |   if (IS_ERR(msg)) {
      |       ^~~~~~


I will add the missing #include <linux/err.h> when merging.

Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

>  			debug("Parsing image's signature failed\n");
> +			msg = NULL;
>  			goto err;
>  		}
>
>