Re: [PATCH][next] integrity: Avoid -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

On 20/03/24 19:19, Mimi Zohar wrote:
> Hi Gustavo,
>
> Sorry for the delay...

No worries. :)

> On Mon, 2024-03-04 at 11:52 -0600, Gustavo A. R. Silva wrote:
> > -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
> > ready to enable it globally.
> >
> > There is currently an object (`hdr)` in `struct ima_max_digest_data`
> > that contains a flexible structure (`struct ima_digest_data`):
> >
> >   struct ima_max_digest_data {
> > 	struct ima_digest_data hdr;
> >          u8 digest[HASH_MAX_DIGESTSIZE];
> >   } __packed;
> >
> > So, in order to avoid ending up with a flexible-array member in the
> > middle of another struct, we use the `struct_group_tagged()` helper to
> > separate the flexible array from the rest of the members in the flexible
> > structure:
> >
> > struct ima_digest_data {
> >          struct_group_tagged(ima_digest_data_hdr, hdr,
> >
> > 	... the rest of the members
> >
> >          );
> >          u8 digest[];
> > } __packed;
> >
> > With the change described above, we can now declare an object of the
> > type of the tagged struct, without embedding the flexible array in the
> > middle of another struct:
> >
> >   struct ima_max_digest_data {
> >          struct ima_digest_data_hdr hdr;
> >          u8 digest[HASH_MAX_DIGESTSIZE];
> >   } __packed;
> >
> > We also use `container_of()` whenever we need to retrieve a pointer to
> > the flexible structure.
>
> Nice!
>
> > So, with these changes, fix the following warnings:
> >
> > security/integrity/evm/evm.h:45:32: warning: structure containing a flexible
> > array member is not at the end of another structure [-Wflex-array-member-not-
> > at-end]
> > security/integrity/evm/evm.h:45:32: warning: structure containing a flexible
> > array member is not at the end of another structure [-Wflex-array-member-not-
> > at-end]
> > security/integrity/evm/evm.h:45:32: warning: structure containing a flexible
> > array member is not at the end of another structure [-Wflex-array-member-not-
> > at-end]
>
> A similar change would need to be made to struct evm_digest:
>
> struct evm_digest {
>          struct ima_digest_data hdr;
>          char digest[IMA_MAX_DIGEST_SIZE];
> } __packed;
>
> Is there are another patch?

Oh, I missed that one. I'll include it and send v2, shortly.

Thanks!
--
Gustavo