Re: efi_loader: pkcs7_parse_message() returns error pointer

[AKASHI Takahiro]

Heinrich,

On Thu, May 07, 2020 at 04:47:22PM +0200, Heinrich Schuchardt wrote:
> 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.
> 
> @Takahiro
> I think we should start documenting the library functions properly. The

Generally I agree, but

> description in lib/crypto/pkcs7_parser.c does not conform to
> https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#function-documentation
> Especially we should describe how errors are returned.

Remember that this file, as well as others under lib/crypto, was
imported from linux kernel source.
I made a minimum set of changes to align it with U-Boot code.
So I'm rather reluctant to modify the file.

Thanks,
-Takahiro Akashi

> Best regards
> 
> Heinrich
> 
> >
> > Signed-off-by: Patrick Wildt 
> >
> > 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)) {
> > debug("Parsing image's signature failed\n");
> > +   msg = NULL;
> > goto err;
> > }
> >
> >
> 

Re: 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 
>
> 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  when merging.

Reviewed-by: Heinrich Schuchardt 

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

Re: 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.

@Takahiro
I think we should start documenting the library functions properly. The
description in lib/crypto/pkcs7_parser.c does not conform to
https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#function-documentation
Especially we should describe how errors are returned.

Best regards

Heinrich

>
> Signed-off-by: Patrick Wildt 
>
> 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)) {
>   debug("Parsing image's signature failed\n");
> + msg = NULL;
>   goto err;
>   }
>
>

efi_loader: pkcs7_parse_message() returns error pointer

[Patrick Wildt]

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 

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