[PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Refactor multiple structs that contain flexible-array members in the
middle by replacing them with unions.

These changes preserve the memory layout while effectively adjusting
it so that the flexible-array member is always treated as the last
member.

With these changes, 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]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v3:
 - Use union instead of DEFINE_RAW_FLEX().

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 | 132 +++++++++++++++++++++++++++++++-------
 1 file changed, 108 insertions(+), 24 deletions(-)

diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
index 3902759abcba..987d427ec2b6 100644
--- a/drivers/acpi/nfit/intel.c
+++ b/drivers/acpi/nfit/intel.c
@@ -55,9 +55,16 @@ static unsigned long intel_security_flags(struct nvdimm *nvdimm,
 {
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
 	unsigned long security_flags = 0;
-	struct {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_get_security_state cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_get_security_state cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
@@ -120,9 +127,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_freeze_lock cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_freeze_lock cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_FREEZE_LOCK,
@@ -153,9 +167,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_set_passphrase cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_set_passphrase cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_family = NVDIMM_FAMILY_INTEL,
@@ -195,9 +216,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_unlock_unit cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_unlock_unit cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_UNLOCK_UNIT,
@@ -234,9 +262,16 @@ static int intel_security_disable(struct nvdimm *nvdimm,
 {
 	int rc;
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
-	struct {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_disable_passphrase cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_disable_passphrase cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_DISABLE_PASSPHRASE,
@@ -277,9 +312,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_secure_erase cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_secure_erase cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_family = NVDIMM_FAMILY_INTEL,
@@ -318,9 +360,16 @@ static int __maybe_unused intel_security_query_overwrite(struct nvdimm *nvdimm)
 {
 	int rc;
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
-	struct {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_query_overwrite cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_query_overwrite cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_QUERY_OVERWRITE,
@@ -354,9 +403,16 @@ static int __maybe_unused intel_security_overwrite(struct nvdimm *nvdimm,
 {
 	int rc;
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
-	struct {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_overwrite cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_overwrite cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_OVERWRITE,
@@ -407,9 +463,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_bus_fw_activate_businfo cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_bus_fw_activate_businfo cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE_BUSINFO,
@@ -518,9 +581,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_bus_fw_activate cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_bus_fw_activate cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE,
@@ -582,9 +652,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_fw_activate_dimminfo cmd;
+		struct {
+			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
+			struct nd_intel_fw_activate_dimminfo cmd;
+		};
 	} nd_cmd = {
 		.pkg = {
 			.nd_command = NVDIMM_INTEL_FW_ACTIVATE_DIMMINFO,
@@ -688,9 +765,16 @@ 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 {
+	/*
+	 * This effectively creates a union between the flexible-array member
+	 * and any members after _offset_to_fam.
+	 */
+	union {
 		struct nd_cmd_pkg pkg;
-		struct nd_intel_fw_activate_arm cmd;
+		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,
-- 
2.43.0

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

Hi all,

Friendly ping: who can review or take this, please? :)

Thanks!
-Gustavo

On 11/06/25 13:52, 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.
> 
> Refactor multiple structs that contain flexible-array members in the
> middle by replacing them with unions.
> 
> These changes preserve the memory layout while effectively adjusting
> it so that the flexible-array member is always treated as the last
> member.
> 
> With these changes, 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]
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes in v3:
>   - Use union instead of DEFINE_RAW_FLEX().
> 
> 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 | 132 +++++++++++++++++++++++++++++++-------
>   1 file changed, 108 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
> index 3902759abcba..987d427ec2b6 100644
> --- a/drivers/acpi/nfit/intel.c
> +++ b/drivers/acpi/nfit/intel.c
> @@ -55,9 +55,16 @@ static unsigned long intel_security_flags(struct nvdimm *nvdimm,
>   {
>   	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
>   	unsigned long security_flags = 0;
> -	struct {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_get_security_state cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_get_security_state cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
> @@ -120,9 +127,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_freeze_lock cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_freeze_lock cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_FREEZE_LOCK,
> @@ -153,9 +167,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_set_passphrase cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_set_passphrase cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_family = NVDIMM_FAMILY_INTEL,
> @@ -195,9 +216,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_unlock_unit cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_unlock_unit cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_UNLOCK_UNIT,
> @@ -234,9 +262,16 @@ static int intel_security_disable(struct nvdimm *nvdimm,
>   {
>   	int rc;
>   	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -	struct {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_disable_passphrase cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_disable_passphrase cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_DISABLE_PASSPHRASE,
> @@ -277,9 +312,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_secure_erase cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_secure_erase cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_family = NVDIMM_FAMILY_INTEL,
> @@ -318,9 +360,16 @@ static int __maybe_unused intel_security_query_overwrite(struct nvdimm *nvdimm)
>   {
>   	int rc;
>   	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -	struct {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_query_overwrite cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_query_overwrite cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_QUERY_OVERWRITE,
> @@ -354,9 +403,16 @@ static int __maybe_unused intel_security_overwrite(struct nvdimm *nvdimm,
>   {
>   	int rc;
>   	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> -	struct {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_overwrite cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_overwrite cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_OVERWRITE,
> @@ -407,9 +463,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_bus_fw_activate_businfo cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_bus_fw_activate_businfo cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE_BUSINFO,
> @@ -518,9 +581,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_bus_fw_activate cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_bus_fw_activate cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_BUS_INTEL_FW_ACTIVATE,
> @@ -582,9 +652,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_fw_activate_dimminfo cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_fw_activate_dimminfo cmd;
> +		};
>   	} nd_cmd = {
>   		.pkg = {
>   			.nd_command = NVDIMM_INTEL_FW_ACTIVATE_DIMMINFO,
> @@ -688,9 +765,16 @@ 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 {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>   		struct nd_cmd_pkg pkg;
> -		struct nd_intel_fw_activate_arm cmd;
> +		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,

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[Kees Cook]

On Wed, Jun 11, 2025 at 01:52:41PM -0600, 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.
> 
> Refactor multiple structs that contain flexible-array members in the
> middle by replacing them with unions.
> 
> These changes preserve the memory layout while effectively adjusting
> it so that the flexible-array member is always treated as the last
> member.
> 
> With these changes, 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]
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes in v3:
>  - Use union instead of DEFINE_RAW_FLEX().

I think your TRAILING_OVERLAP macro[1] is perfect here. I'll try to get that
landed for the next rc. Can you double-check that this works correctly
in these cases?

> @@ -55,9 +55,16 @@ static unsigned long intel_security_flags(struct nvdimm *nvdimm,
>  {
>  	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
>  	unsigned long security_flags = 0;
> -	struct {
> +	/*
> +	 * This effectively creates a union between the flexible-array member
> +	 * and any members after _offset_to_fam.
> +	 */
> +	union {
>  		struct nd_cmd_pkg pkg;
> -		struct nd_intel_get_security_state cmd;
> +		struct {
> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
> +			struct nd_intel_get_security_state cmd;
> +		};
>  	} nd_cmd = {
>  		.pkg = {
>  			.nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,

I think it would be a pretty small and direct replacement:

	TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
			 struct nd_intel_get_security_state cmd;
	) nd_cmd = {
		...

-Kees

[1] https://web.git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/kspp&id=29bb79e9dbf1ba100125e39deb7147acd490903f

-- 
Kees Cook

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

On 25/06/25 10:56, Kees Cook wrote:
> On Wed, Jun 11, 2025 at 01:52:41PM -0600, 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.
>>
>> Refactor multiple structs that contain flexible-array members in the
>> middle by replacing them with unions.
>>
>> These changes preserve the memory layout while effectively adjusting
>> it so that the flexible-array member is always treated as the last
>> member.
>>
>> With these changes, 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]
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>> Changes in v3:
>>   - Use union instead of DEFINE_RAW_FLEX().
> 
> I think your TRAILING_OVERLAP macro[1] is perfect here. I'll try to get that
> landed for the next rc. Can you double-check that this works correctly
> in these cases?

Absolutely. If people prefer that route I'm happy to wait for the helper to
land in linus' tree.

> 
>> @@ -55,9 +55,16 @@ static unsigned long intel_security_flags(struct nvdimm *nvdimm,
>>   {
>>   	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
>>   	unsigned long security_flags = 0;
>> -	struct {
>> +	/*
>> +	 * This effectively creates a union between the flexible-array member
>> +	 * and any members after _offset_to_fam.
>> +	 */
>> +	union {
>>   		struct nd_cmd_pkg pkg;
>> -		struct nd_intel_get_security_state cmd;
>> +		struct {
>> +			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
>> +			struct nd_intel_get_security_state cmd;
>> +		};
>>   	} nd_cmd = {
>>   		.pkg = {
>>   			.nd_command = NVDIMM_INTEL_GET_SECURITY_STATE,
> 
> I think it would be a pretty small and direct replacement:
> 
> 	TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> 			 struct nd_intel_get_security_state cmd;
> 	) nd_cmd = {
> 		...

Yes, this works. Hopefully, maintainers will comment on this and let us
know what they prefer. :)

Thanks!
-Gustavo

> 
> -Kees
> 
> [1] https://web.git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/kspp&id=29bb79e9dbf1ba100125e39deb7147acd490903f
> 

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[dan.j.williams]

Gustavo A. R. Silva wrote:
[..]
> > I think it would be a pretty small and direct replacement:
> > 
> > 	TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> > 			 struct nd_intel_get_security_state cmd;
> > 	) nd_cmd = {
> > 		...
> 
> Yes, this works. Hopefully, maintainers will comment on this and let us
> know what they prefer. :)

Hey Gustavo, apologies for the latency here. I think TRAILING_OVERLAP()
looks lovely for this if only because I can read that and have an idea
what it means vs wondering what this _offset_to_fam is about and needing
to read the comment.

If you can get me that patch on top of the TRAILING_OVERLAP() branch I
can test it out and ack it to let it do in through the KSPP tree.

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[dan.j.williams]

dan.j.williams@ wrote:
> Gustavo A. R. Silva wrote:
> [..]
> > > I think it would be a pretty small and direct replacement:
> > > 
> > > 	TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> > > 			 struct nd_intel_get_security_state cmd;
> > > 	) nd_cmd = {
> > > 		...
> > 
> > Yes, this works. Hopefully, maintainers will comment on this and let us
> > know what they prefer. :)
> 
> Hey Gustavo, apologies for the latency here. I think TRAILING_OVERLAP()
> looks lovely for this if only because I can read that and have an idea
> what it means vs wondering what this _offset_to_fam is about and needing
> to read the comment.
> 
> If you can get me that patch on top of the TRAILING_OVERLAP() branch I
> can test it out and ack it to let it do in through the KSPP tree.

Just to move this along, I gave this conversion a try and all looks good
here. So feel free to fold this in and add:

Acked-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>

...and take it through the KSPP tree with the TRAILING_OVERLAP() merge.

-- 8< --
diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
index 987d427ec2b6..c88647428715 100644
--- a/drivers/acpi/nfit/intel.c
+++ b/drivers/acpi/nfit/intel.c
@@ -55,17 +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;
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -127,17 +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);
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -167,17 +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;
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -216,17 +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);
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -262,17 +230,9 @@ static int intel_security_disable(struct nvdimm *nvdimm,
 {
 	int rc;
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -312,17 +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;
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -360,17 +312,9 @@ static int __maybe_unused intel_security_query_overwrite(struct nvdimm *nvdimm)
 {
 	int rc;
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -403,17 +347,9 @@ static int __maybe_unused intel_security_overwrite(struct nvdimm *nvdimm,
 {
 	int rc;
 	struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -463,17 +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)
 {
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -581,17 +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);
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -652,17 +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)
 {
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	union {
-		struct nd_cmd_pkg pkg;
-		struct {
-			u8 _offset_to_fam[offsetof(struct nd_cmd_pkg, nd_payload)];
-			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,
@@ -765,17 +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;
-	/*
-	 * This effectively creates a union between the flexible-array member
-	 * and any members after _offset_to_fam.
-	 */
-	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 = {
+	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,

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

On 25/06/25 15:08, dan.j.williams@intel.com wrote:
> dan.j.williams@ wrote:
>> Gustavo A. R. Silva wrote:
>> [..]
>>>> I think it would be a pretty small and direct replacement:
>>>>
>>>> 	TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
>>>> 			 struct nd_intel_get_security_state cmd;
>>>> 	) nd_cmd = {
>>>> 		...
>>>
>>> Yes, this works. Hopefully, maintainers will comment on this and let us
>>> know what they prefer. :)
>>
>> Hey Gustavo, apologies for the latency here. I think TRAILING_OVERLAP()
>> looks lovely for this if only because I can read that and have an idea
>> what it means vs wondering what this _offset_to_fam is about and needing
>> to read the comment.
>>
>> If you can get me that patch on top of the TRAILING_OVERLAP() branch I
>> can test it out and ack it to let it do in through the KSPP tree.
> 
> Just to move this along, I gave this conversion a try and all looks good
> here. So feel free to fold this in and add:
> 
> Acked-by: Dan Williams <dan.j.williams@intel.com>
> Tested-by: Dan Williams <dan.j.williams@intel.com>
> 
> ...and take it through the KSPP tree with the TRAILING_OVERLAP() merge.

Thank you, Dan! :)

-Gustavo

Re: [PATCH v3][next] acpi: nfit: intel: avoid multiple -Wflex-array-member-not-at-end warnings

[dan.j.williams]

Gustavo A. R. Silva wrote:
> 
> 
> On 25/06/25 15:08, dan.j.williams@intel.com wrote:
> > dan.j.williams@ wrote:
> >> Gustavo A. R. Silva wrote:
> >> [..]
> >>>> I think it would be a pretty small and direct replacement:
> >>>>
> >>>> 	TRAILING_OVERLAP(struct nd_cmd_pkg, pkg, nd_payload,
> >>>> 			 struct nd_intel_get_security_state cmd;
> >>>> 	) nd_cmd = {
> >>>> 		...
> >>>
> >>> Yes, this works. Hopefully, maintainers will comment on this and let us
> >>> know what they prefer. :)
> >>
> >> Hey Gustavo, apologies for the latency here. I think TRAILING_OVERLAP()
> >> looks lovely for this if only because I can read that and have an idea
> >> what it means vs wondering what this _offset_to_fam is about and needing
> >> to read the comment.
> >>
> >> If you can get me that patch on top of the TRAILING_OVERLAP() branch I
> >> can test it out and ack it to let it do in through the KSPP tree.
> > 
> > Just to move this along, I gave this conversion a try and all looks good
> > here. So feel free to fold this in and add:
> > 
> > Acked-by: Dan Williams <dan.j.williams@intel.com>
> > Tested-by: Dan Williams <dan.j.williams@intel.com>
> > 
> > ...and take it through the KSPP tree with the TRAILING_OVERLAP() merge.
> 
> Thank you, Dan! :)

Uh oh, I spoke too soon. I saw most of the tests pass when I sent that
mail, but the firmware-update.sh regresses. It passes on vanilla
v6.16-rc3 and fails with both the original open-coded _offset_to_fam[]
approach and TRAILING_OVERLAP() conversion.

Let me try to get some more debug info.

The test is:

meson test -C build firmware-update.sh 

...from the ndctl project:

https://github.com/pmem/ndctl