Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix a dozen instances of
> the following type of warning:
> 
> drivers/acpi/nfit/intel.c:692:35: warning: structure containing a flexible 
> array member is not at the end of another structure 
> [-Wflex-array-member-not-at-end]
> 
> Acked-by: Dan Williams <[email protected]>
> Tested-by: Dan Williams <[email protected]>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> This patch should go through:
> https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/ 
> (for-next/hardening)
> 
> Changes in v4:
>  - Use the new TRAILING_OVERLAP() helper.
> 
> Changes in v3:
>  - Use union instead of DEFINE_RAW_FLEX().
>  - Link: https://lore.kernel.org/linux-hardening/aEneid7gdAZr1_kR@kspp/
> 
> Changes in v2:
>  - Use DEFINE_RAW_FLEX() instead of __struct_group().
>  - Link: https://lore.kernel.org/linux-hardening/Z-QpUcxFCRByYcTA@kspp/ 
> 
> v1:
>  - Link: https://lore.kernel.org/linux-hardening/Z618ILbAR8YAvTkd@kspp/
> 
>  drivers/acpi/nfit/intel.c | 84 +++++++++++++++++----------------------
>  1 file changed, 36 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
> index 3902759abcba..d0b72e906428 100644
> --- a/drivers/acpi/nfit/intel.c
> +++ b/drivers/acpi/nfit/intel.c
> @@ -55,10 +55,9 @@ static unsigned long intel_security_flags(struct nvdimm 
> *nvdimm,
>  {
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
>       unsigned long security_flags = 0;
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_get_security_state cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_get_security_state cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -120,10 +119,9 @@ static unsigned long intel_security_flags(struct nvdimm 
> *nvdimm,
>  static int intel_security_freeze(struct nvdimm *nvdimm)
>  {
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_freeze_lock cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_freeze_lock cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_FREEZE_LOCK,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -153,10 +151,9 @@ static int intel_security_change_key(struct nvdimm 
> *nvdimm,
>       unsigned int cmd = ptype == NVDIMM_MASTER ?
>               NVDIMM_INTEL_SET_MASTER_PASSPHRASE :
>               NVDIMM_INTEL_SET_PASSPHRASE;
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_set_passphrase cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_set_passphrase cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_family = NVDIMM_FAMILY_INTEL,
>                       .nd_size_in = ND_INTEL_PASSPHRASE_SIZE * 2,
> @@ -195,10 +192,9 @@ static int __maybe_unused intel_security_unlock(struct 
> nvdimm *nvdimm,
>               const struct nvdimm_key_data *key_data)
>  {
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_unlock_unit cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_unlock_unit cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_UNLOCK_UNIT,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -234,10 +230,9 @@ static int intel_security_disable(struct nvdimm *nvdimm,
>  {
>       int rc;
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_disable_passphrase cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_disable_passphrase cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_DISABLE_PASSPHRASE,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -277,10 +272,9 @@ static int __maybe_unused intel_security_erase(struct 
> nvdimm *nvdimm,
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
>       unsigned int cmd = ptype == NVDIMM_MASTER ?
>               NVDIMM_INTEL_MASTER_SECURE_ERASE : NVDIMM_INTEL_SECURE_ERASE;
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_secure_erase cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_secure_erase cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_family = NVDIMM_FAMILY_INTEL,
>                       .nd_size_in = ND_INTEL_PASSPHRASE_SIZE,
> @@ -318,10 +312,9 @@ static int __maybe_unused 
> intel_security_query_overwrite(struct nvdimm *nvdimm)
>  {
>       int rc;
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_query_overwrite cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_query_overwrite cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_QUERY_OVERWRITE,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -354,10 +347,9 @@ static int __maybe_unused 
> intel_security_overwrite(struct nvdimm *nvdimm,
>  {
>       int rc;
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_overwrite cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_overwrite cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_OVERWRITE,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -407,10 +399,9 @@ const struct nvdimm_security_ops *intel_security_ops = 
> &__intel_security_ops;
>  static int intel_bus_fwa_businfo(struct nvdimm_bus_descriptor *nd_desc,
>               struct nd_intel_bus_fw_activate_businfo *info)
>  {
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_bus_fw_activate_businfo cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_bus_fw_activate_businfo cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE_BUSINFO,
>                       .nd_family = NVDIMM_BUS_FAMILY_INTEL,
> @@ -518,10 +509,9 @@ static enum nvdimm_fwa_capability 
> intel_bus_fwa_capability(
>  static int intel_bus_fwa_activate(struct nvdimm_bus_descriptor *nd_desc)
>  {
>       struct acpi_nfit_desc *acpi_desc = to_acpi_desc(nd_desc);
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_bus_fw_activate cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_bus_fw_activate cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE,
>                       .nd_family = NVDIMM_BUS_FAMILY_INTEL,
> @@ -582,10 +572,9 @@ const struct nvdimm_bus_fw_ops *intel_bus_fw_ops = 
> &__intel_bus_fw_ops;
>  static int intel_fwa_dimminfo(struct nvdimm *nvdimm,
>               struct nd_intel_fw_activate_dimminfo *info)
>  {
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_fw_activate_dimminfo cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_fw_activate_dimminfo cmd;
> +     ) nd_cmd = {
>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_FW_ACTIVATE_DIMMINFO,
>                       .nd_family = NVDIMM_FAMILY_INTEL,
> @@ -688,10 +677,9 @@ static int intel_fwa_arm(struct nvdimm *nvdimm, enum 
> nvdimm_fwa_trigger arm)
>  {
>       struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
>       struct acpi_nfit_desc *acpi_desc = nfit_mem->acpi_desc;
> -     struct {
> -             struct nd_cmd_pkg pkg;
> -             struct nd_intel_fw_activate_arm cmd;
> -     } nd_cmd = {
> +     TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> +                      struct nd_intel_fw_activate_arm cmd;
> +     ) nd_cmd = {

The regression is here.


>               .pkg = {
>                       .nd_command = NVDIMM_INTEL_FW_ACTIVATE_ARM,
>                       .nd_family = NVDIMM_FAMILY_INTEL,

So the full context is this:

        union {
                struct nd_cmd_pkg pkg;
                struct {
                        u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, 
nd_payload)];
                        struct nd_intel_fw_activate_arm cmd;
                };
        } nd_cmd = {
                .pkg = {
                        .nd_command = NVDIMM_INTEL_FW_ACTIVATE_ARM,
                        .nd_family = NVDIMM_FAMILY_INTEL,
                        .nd_size_in = sizeof(nd_cmd.cmd.activate_arm),
                        .nd_size_out =
                                sizeof(struct nd_intel_fw_activate_arm),
                        .nd_fw_size =
                                sizeof(struct nd_intel_fw_activate_arm),
                },
                .cmd = {
                        .activate_arm = arm == NVDIMM_FWA_ARM
                                ? ND_INTEL_DIMM_FWA_ARM
                                : ND_INTEL_DIMM_FWA_DISARM,
                },
        };

The problem is that the designated initialization of .cmd zeroes out the
.pkg portion of the union. This incremental change works, and with it
folded you can keep my Acked-by and Tested-by on v5.

You might want to remind folks about this designated initializer trap in
the kdoc for TRAILING_OVERLAP().

-- 8< --
diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
index c88647428715..c63284ce9a87 100644
--- a/drivers/acpi/nfit/intel.c
+++ b/drivers/acpi/nfit/intel.c
@@ -511,29 +511,27 @@ static int intel_bus_fwa_activate(struct 
nvdimm_bus_descriptor *nd_desc)
        struct acpi_nfit_desc *acpi_desc = to_acpi_desc(nd_desc);
         TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
                          struct nd_intel_bus_fw_activate cmd;
-        ) nd_cmd = {
-               .pkg = {
-                       .nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE,
-                       .nd_family = NVDIMM_BUS_FAMILY_INTEL,
-                       .nd_size_in = sizeof(nd_cmd.cmd.iodev_state),
-                       .nd_size_out =
-                               sizeof(struct nd_intel_bus_fw_activate),
-                       .nd_fw_size =
-                               sizeof(struct nd_intel_bus_fw_activate),
-               },
+        ) nd_cmd;
+       int rc;
+
+       nd_cmd.pkg = (struct nd_cmd_pkg) {
+               .nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE,
+               .nd_family = NVDIMM_BUS_FAMILY_INTEL,
+               .nd_size_in = sizeof(nd_cmd.cmd.iodev_state),
+               .nd_size_out = sizeof(struct nd_intel_bus_fw_activate),
+               .nd_fw_size = sizeof(struct nd_intel_bus_fw_activate),
+       };
+       nd_cmd.cmd = (struct nd_intel_bus_fw_activate) {
                /*
                 * Even though activate is run from a suspended context,
                 * for safety, still ask platform firmware to force
                 * quiesce devices by default. Let a module
                 * parameter override that policy.
                 */
-               .cmd = {
-                       .iodev_state = acpi_desc->fwa_noidle
-                               ? ND_INTEL_BUS_FWA_IODEV_OS_IDLE
-                               : ND_INTEL_BUS_FWA_IODEV_FORCE_IDLE,
-               },
+               .iodev_state = acpi_desc->fwa_noidle ?
+                                      ND_INTEL_BUS_FWA_IODEV_OS_IDLE :
+                                      ND_INTEL_BUS_FWA_IODEV_FORCE_IDLE,
        };
-       int rc;
 
        switch (intel_bus_fwa_state(nd_desc)) {
        case NVDIMM_FWA_ARMED:
@@ -679,24 +677,22 @@ static int intel_fwa_arm(struct nvdimm *nvdimm, enum 
nvdimm_fwa_trigger arm)
        struct acpi_nfit_desc *acpi_desc = nfit_mem->acpi_desc;
        TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
                         struct nd_intel_fw_activate_arm cmd;
-       ) nd_cmd = {
-               .pkg = {
-                       .nd_command = NVDIMM_INTEL_FW_ACTIVATE_ARM,
-                       .nd_family = NVDIMM_FAMILY_INTEL,
-                       .nd_size_in = sizeof(nd_cmd.cmd.activate_arm),
-                       .nd_size_out =
-                               sizeof(struct nd_intel_fw_activate_arm),
-                       .nd_fw_size =
-                               sizeof(struct nd_intel_fw_activate_arm),
-               },
-               .cmd = {
-                       .activate_arm = arm == NVDIMM_FWA_ARM
-                               ? ND_INTEL_DIMM_FWA_ARM
-                               : ND_INTEL_DIMM_FWA_DISARM,
-               },
-       };
+       ) nd_cmd;
        int rc;
 
+       nd_cmd.pkg = (struct nd_cmd_pkg) {
+               .nd_command = NVDIMM_INTEL_FW_ACTIVATE_ARM,
+               .nd_family = NVDIMM_FAMILY_INTEL,
+               .nd_size_in = sizeof(nd_cmd.cmd.activate_arm),
+               .nd_size_out = sizeof(struct nd_intel_fw_activate_arm),
+               .nd_fw_size = sizeof(struct nd_intel_fw_activate_arm),
+       };
+       nd_cmd.cmd = (struct nd_intel_fw_activate_arm) {
+               .activate_arm = arm == NVDIMM_FWA_ARM ?
+                                       ND_INTEL_DIMM_FWA_ARM :
+                                       ND_INTEL_DIMM_FWA_DISARM,
+       };
+
        switch (intel_fwa_state(nvdimm)) {
        case NVDIMM_FWA_INVALID:
                return -ENXIO;

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