treewide: Replace zero-length arrays with flexible-array members

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

This code was transformed with the help of Coccinelle:
(next-20220214$ spatch --jobs $(getconf _NPROCESSORS_ONLN) --sp-file script.cocci --include-headers --dir . > output.patch)

@@
identifier S, member, array;
type T1, T2;
@@

struct S {
  ...
  T1 member;
  T2 array[
- 0
  ];
};

UAPI and wireless changes were intentionally excluded from this patch
and will be sent out separately.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/78
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

arch/alpha/include/asm/hwrpb.h

@@ -152,7 +152,7 @@ struct memdesc_struct {
 	unsigned long chksum;
 	unsigned long optional_pa;
 	unsigned long numclusters;
-	struct memclust_struct cluster[0];
+	struct memclust_struct cluster[];
 };
 
 struct dsr_struct {

arch/ia64/include/asm/sal.h

@@ -420,7 +420,7 @@ typedef struct sal_log_processor_info {
 	 * The rest of this structure consists of variable-length arrays, which can't be
 	 * expressed in C.
 	 */
-	sal_log_mod_error_info_t info[0];
+	sal_log_mod_error_info_t info[];
 	/*
 	 * This is what the rest looked like if C supported variable-length arrays:
 	 *

arch/s390/include/asm/ccwgroup.h

@@ -25,7 +25,7 @@ struct ccwgroup_device {
 	unsigned int count;
 	struct device	dev;
 	struct work_struct ungroup_work;
-	struct ccw_device *cdev[0];
+	struct ccw_device *cdev[];
 };
 
 /**

arch/s390/include/asm/chsc.h

@@ -63,7 +63,7 @@ struct chsc_pnso_area {
 	struct chsc_header response;
 	u32:32;
 	struct chsc_pnso_naihdr naihdr;
-	struct chsc_pnso_naid_l2 entries[0];
+	struct chsc_pnso_naid_l2 entries[];
 } __packed __aligned(PAGE_SIZE);
 
 #endif /* _ASM_S390_CHSC_H */

arch/s390/include/asm/eadm.h

@@ -78,7 +78,7 @@ struct aob {
 
 struct aob_rq_header {
 	struct scm_device *scmdev;
-	char data[0];
+	char data[];
 };
 
 struct scm_device {

arch/s390/include/asm/fcx.h

@@ -214,7 +214,7 @@ struct dcw_intrg_data {
 	u32 :32;
 	u64 time;
 	u64 prog_id;
-	u8  prog_data[0];
+	u8  prog_data[];
 } __attribute__ ((packed));
 
 #define DCW_FLAGS_CC		(1 << (7 - 1))
@@ -241,7 +241,7 @@ struct dcw {
 	u32 :8;
 	u32 cd_count:8;
 	u32 count;
-	u8 cd[0];
+	u8 cd[];
 } __attribute__ ((packed));
 
 #define TCCB_FORMAT_DEFAULT	0x7f

arch/s390/include/asm/idals.h

@@ -108,7 +108,7 @@ clear_normalized_cda(struct ccw1 * ccw)
 struct idal_buffer {
 	size_t size;
 	size_t page_order;
-	void *data[0];
+	void *data[];
 };
 
 /*

arch/s390/include/asm/sclp.h

@@ -112,7 +112,7 @@ struct zpci_report_error_header {
 			 *	(OpenCrypto Successful Diagnostics Execution)
 			 */
 	u16 length;	/* Length of Subsequent Data (up to 4K – SCLP header */
-	u8 data[0];	/* Subsequent Data passed verbatim to SCLP ET 24 */
+	u8 data[];	/* Subsequent Data passed verbatim to SCLP ET 24 */
 } __packed;
 
 extern char *sclp_early_sccb;

arch/s390/include/asm/sysinfo.h

@@ -67,12 +67,12 @@ struct sysinfo_1_2_2 {
 	unsigned short cpus_configured;
 	unsigned short cpus_standby;
 	unsigned short cpus_reserved;
-	unsigned short adjustment[0];
+	unsigned short adjustment[];
 };
 
 struct sysinfo_1_2_2_extension {
 	unsigned int alt_capability;
-	unsigned short alt_adjustment[0];
+	unsigned short alt_adjustment[];
 };
 
 struct sysinfo_2_2_1 {
@@ -181,7 +181,7 @@ struct sysinfo_15_1_x {
 	unsigned char reserved1;
 	unsigned char mnest;
 	unsigned char reserved2[4];
-	union topology_entry tle[0];
+	union topology_entry tle[];
 };
 
 int stsi(void *sysinfo, int fc, int sel1, int sel2);

arch/sh/include/asm/thread_info.h

@@ -33,7 +33,7 @@ struct thread_info {
 	mm_segment_t		addr_limit;	/* thread address space */
 	unsigned long		previous_sp;	/* sp of previous stack in case
 						   of nested IRQ stacks */
-	__u8			supervisor_stack[0];
+	__u8			supervisor_stack[];
 };
 
 #endif

arch/sparc/include/asm/vio.h

@@ -70,7 +70,7 @@ struct vio_dring_register {
 #define VIO_RX_DRING_DATA	0x0004
 	u16			resv;
 	u32			num_cookies;
-	struct ldc_trans_cookie	cookies[0];
+	struct ldc_trans_cookie	cookies[];
 };
 
 struct vio_dring_unregister {
@@ -161,7 +161,7 @@ struct vio_disk_desc {
 	u64			size;
 	u32			ncookies;
 	u32			resv2;
-	struct ldc_trans_cookie	cookies[0];
+	struct ldc_trans_cookie	cookies[];
 };
 
 #define VIO_DISK_VNAME_LEN	8
@@ -200,13 +200,13 @@ struct vio_disk_devid {
 	u16			resv;
 	u16			type;
 	u32			len;
-	char			id[0];
+	char			id[];
 };
 
 struct vio_disk_efi {
 	u64			lba;
 	u64			len;
-	char			data[0];
+	char			data[];
 };
 
 /* VIO net specific structures and defines */
@@ -246,7 +246,7 @@ struct vio_net_desc {
 	struct vio_dring_hdr	hdr;
 	u32			size;
 	u32			ncookies;
-	struct ldc_trans_cookie	cookies[0];
+	struct ldc_trans_cookie	cookies[];
 };
 
 struct vio_net_dext {

arch/um/include/shared/net_kern.h

@@ -39,7 +39,7 @@ struct uml_net_private {
 
 	void (*add_address)(unsigned char *, unsigned char *, void *);
 	void (*delete_address)(unsigned char *, unsigned char *, void *);
-	char user[0];
+	char user[];
 };
 
 struct net_kern_info {

arch/x86/include/asm/microcode_amd.h

@@ -38,7 +38,7 @@ struct microcode_header_amd {
 
 struct microcode_amd {
 	struct microcode_header_amd	hdr;
-	unsigned int			mpb[0];
+	unsigned int			mpb[];
 };
 
 #define PATCH_MAX_SIZE (3 * PAGE_SIZE)

arch/x86/include/asm/microcode_intel.h

@@ -19,7 +19,7 @@ struct microcode_header_intel {
 
 struct microcode_intel {
 	struct microcode_header_intel hdr;
-	unsigned int            bits[0];
+	unsigned int            bits[];
 };
 
 /* microcode format is extended from prescott processors */
@@ -33,7 +33,7 @@ struct extended_sigtable {
 	unsigned int            count;
 	unsigned int            cksum;
 	unsigned int            reserved[3];
-	struct extended_signature sigs[0];
+	struct extended_signature sigs[];
 };
 
 #define DEFAULT_UCODE_DATASIZE	(2000)

arch/x86/include/asm/pci.h

@@ -135,7 +135,7 @@ struct pci_setup_rom {
 	unsigned long bus;
 	unsigned long device;
 	unsigned long function;
-	uint8_t romdata[0];
+	uint8_t romdata[];
 };
 
 #endif /* _ASM_X86_PCI_H */

arch/x86/include/asm/pci_x86.h

@@ -87,7 +87,7 @@ struct irq_routing_table {
 	u32 miniport_data;		/* Crap */
 	u8 rfu[11];
 	u8 checksum;			/* Modulo 256 checksum must give 0 */
-	struct irq_info slots[0];
+	struct irq_info slots[];
 } __attribute__((packed));
 
 extern unsigned int pcibios_irq_mask;

arch/xtensa/include/asm/bootparam.h

@@ -34,7 +34,7 @@
 typedef struct bp_tag {
 	unsigned short id;	/* tag id */
 	unsigned short size;	/* size of this record excluding the structure*/
-	unsigned long data[0];	/* data */
+	unsigned long data[];	/* data */
 } bp_tag_t;
 
 struct bp_meminfo {

drivers/crypto/caam/pdb.h

@@ -144,7 +144,7 @@ struct ipsec_encap_pdb {
 	};
 	u32 spi;
 	u32 ip_hdr_len;
-	u32 ip_hdr[0];
+	u32 ip_hdr[];
 };
 
 /**

drivers/gpu/drm/i915/gt/uc/intel_guc_ads.c

@@ -51,7 +51,7 @@ struct __guc_ads_blob {
 	struct guc_gt_system_info system_info;
 	struct guc_engine_usage engine_usage;
 	/* From here on, location is dynamic! Refer to above diagram. */
-	struct guc_mmio_reg regset[0];
+	struct guc_mmio_reg regset[];
 } __packed;
 
 static u32 guc_ads_regset_size(struct intel_guc *guc)

drivers/gpu/drm/nouveau/include/nvfw/hs.h

@@ -23,7 +23,7 @@ struct nvfw_hs_load_header {
 	u32 data_dma_base;
 	u32 data_size;
 	u32 num_apps;
-	u32 apps[0];
+	u32 apps[];
 };
 
 const struct nvfw_hs_load_header *