Re: [PATCH v3][next] integrity: Avoid -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

On 3/21/24 07:58, Mimi Zohar wrote:
> On Wed, 2024-03-20 at 22:11 -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 a struct, we use the `__struct_group()` helper to separate
> > the flexible array from the rest of the members in the flexible
> > structure:
> >
> > struct ima_digest_data {
> >          __struct_group(ima_digest_data_hdr, hdr, __packed,
> >
> > 	... 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 ima_digest_data_hdr`, 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;
>
> And similarly for 'struct evm_digest'.

Yes. :)

> > We also use `container_of()` whenever we need to retrieve a pointer to
> > the flexible structure.
> >
> > 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]
>
> I assume these messages are gone.

Yes. :)

Thanks
--
Gustavo