On Thu, 2024-04-04 at 12:49 -0400, Mimi Zohar wrote:
> Hi Gustavo,
>
> On Thu, 2024-04-04 at 09:00 -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;
> >
> > And similarly for `struct evm_ima_xattr_data`.
> >
> > 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` and `struct evm_xattr`.
> >
> > 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:64:32: warning: structure containing a flexible
> > array member is not at the end of another structure [-Wflex-array-member-
> > not-
> > at-end]
> > security/integrity/evm/../integrity.h:40:35: warning: structure containing a
> > flexible array member is not at the end of another structure [-Wflex-array-
> > member-not-at-end]
> > security/integrity/evm/../integrity.h:68:32: warning: structure containing a
> > flexible array member is not at the end of another structure [-Wflex-array-
> > member-not-at-end]
> > security/integrity/ima/../integrity.h:40:35: warning: structure containing a
> > flexible array member is not at the end of another structure [-Wflex-array-
> > member-not-at-end]
> > security/integrity/ima/../integrity.h:68:32: warning: structure containing a
> > flexible array member is not at the end of another structure [-Wflex-array-
> > member-not-at-end]
> > security/integrity/integrity.h:40:35: warning: structure containing a
> > flexible
> > array member is not at the end of another structure [-Wflex-array-member-
> > not-
> > at-end]
> > security/integrity/integrity.h:68:32: warning: structure containing a
> > flexible
> > array member is not at the end of another structure [-Wflex-array-member-
> > not-
> > at-end]
> > security/integrity/platform_certs/../integrity.h:40:35: warning: structure
> > containing a flexible array member is not at the end of another structure [-
> > Wflex-array-member-not-at-end]
> > security/integrity/platform_certs/../integrity.h:68:32: warning: structure
> > containing a flexible array member is not at the end of another structure [-
> > Wflex-array-member-not-at-end]
> >
> > Link: https://github.com/KSPP/linux/issues/202
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
>
> Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
>
> Thanks, Gustavo. I already applied and tested v4, but was trying to actually
> see the errors with before pushing it out.
With GCC-14, I'm seeing the "warning: structure containing a flexible array
member is not at the end of another structure [-Wflex-array-member-not-at-end]"
messages. As expected, with the patch no warnings.
"checkpatch.pl --strict" complains "CHECK: Alignment should match open
parenthesis". I'll queue the patch, but how about teaching checkpatch.pl to
ignore __struct_group()?
thanks,
Mimi
