treewide: uapi: 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:
(linux-5.19-rc2$ 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
  ];
};

-fstrict-flex-arrays=3 is coming and we need to land these changes
to prevent issues like these in the short future:

../fs/minix/dir.c:337:3: warning: 'strcpy' will always overflow; destination buffer has size 0,
but the source string has length 2 (including NUL byte) [-Wfortify-source]
		strcpy(de3->name, ".");
		^

Since these are all [0] to [] changes, the risk to UAPI is nearly zero. If
this breaks anything, we can use a union with a new member name.

[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
Build-tested-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/62b675ec.wKX6AOZ6cbE71vtF%25lkp@intel.com/
Acked-by: Dan Williams <dan.j.williams@intel.com> # For ndctl.h
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

9 files changed, 17 insertions, 17 deletions

diff --git a/tools/include/uapi/drm/i915_drm.h b/tools/include/uapi/drm/i915_drm.h
index 05c3642aaece..239b91b13c60 100644
--- a/tools/include/uapi/drm/i915_drm.h
+++ b/tools/include/uapi/drm/i915_drm.h
@@ -2060,7 +2060,7 @@ struct i915_context_engines_load_balance {
 
 	__u64 mbz64; /* reserved for future use; must be zero */
 
-	struct i915_engine_class_instance engines[0];
+	struct i915_engine_class_instance engines[];
 } __attribute__((packed));
 
 #define I915_DEFINE_CONTEXT_ENGINES_LOAD_BALANCE(name__, N__) struct { \
@@ -2098,7 +2098,7 @@ struct i915_context_engines_bond {
 	__u64 flags; /* all undefined flags must be zero */
 	__u64 mbz64[4]; /* reserved for future use; must be zero */
 
-	struct i915_engine_class_instance engines[0];
+	struct i915_engine_class_instance engines[];
 } __attribute__((packed));
 
 #define I915_DEFINE_CONTEXT_ENGINES_BOND(name__, N__) struct { \
@@ -2225,7 +2225,7 @@ struct i915_context_engines_parallel_submit {
 	 * length = width (i) * num_siblings (j)
 	 * index = j + i * num_siblings
 	 */
-	struct i915_engine_class_instance engines[0];
+	struct i915_engine_class_instance engines[];
 
 } __packed;
 
diff --git a/tools/include/uapi/linux/fs.h b/tools/include/uapi/linux/fs.h
index bdf7b404b3e7..b7b56871029c 100644
--- a/tools/include/uapi/linux/fs.h
+++ b/tools/include/uapi/linux/fs.h
@@ -90,7 +90,7 @@ struct file_dedupe_range {
 	__u16 dest_count;	/* in - total elements in info array */
 	__u16 reserved1;	/* must be zero */
 	__u32 reserved2;	/* must be zero */
-	struct file_dedupe_range_info info[0];
+	struct file_dedupe_range_info info[];
 };
 
 /* And dynamically-tunable limits and defaults: */
diff --git a/tools/include/uapi/linux/if_tun.h b/tools/include/uapi/linux/if_tun.h
index 454ae31b93c7..2ec07de1d73b 100644
--- a/tools/include/uapi/linux/if_tun.h
+++ b/tools/include/uapi/linux/if_tun.h
@@ -108,7 +108,7 @@ struct tun_pi {
 struct tun_filter {
 	__u16  flags; /* TUN_FLT_ flags see above */
 	__u16  count; /* Number of addresses */
-	__u8   addr[0][ETH_ALEN];
+	__u8   addr[][ETH_ALEN];
 };
 
 #endif /* _UAPI__IF_TUN_H */
diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
index 6a184d260c7f..37ce8cbac322 100644
--- a/tools/include/uapi/linux/kvm.h
+++ b/tools/include/uapi/linux/kvm.h
@@ -539,7 +539,7 @@ struct kvm_coalesced_mmio {
 
 struct kvm_coalesced_mmio_ring {
 	__u32 first, last;
-	struct kvm_coalesced_mmio coalesced_mmio[0];
+	struct kvm_coalesced_mmio coalesced_mmio[];
 };
 
 #define KVM_COALESCED_MMIO_MAX \
@@ -618,7 +618,7 @@ struct kvm_clear_dirty_log {
 /* for KVM_SET_SIGNAL_MASK */
 struct kvm_signal_mask {
 	__u32 len;
-	__u8  sigset[0];
+	__u8  sigset[];
 };
 
 /* for KVM_TPR_ACCESS_REPORTING */
@@ -1216,7 +1216,7 @@ struct kvm_irq_routing_entry {
 struct kvm_irq_routing {
 	__u32 nr;
 	__u32 flags;
-	struct kvm_irq_routing_entry entries[0];
+	struct kvm_irq_routing_entry entries[];
 };
 
 #endif
@@ -1335,7 +1335,7 @@ struct kvm_dirty_tlb {
 
 struct kvm_reg_list {
 	__u64 n; /* number of regs */
-	__u64 reg[0];
+	__u64 reg[];
 };
 
 struct kvm_one_reg {
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index d37629dbad72..4653834f078f 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -491,7 +491,7 @@ struct perf_event_query_bpf {
 	/*
 	 * User provided buffer to store program ids
 	 */
-	__u32	ids[0];
+	__u32	ids[];
 };
 
 /*
diff --git a/tools/include/uapi/linux/pkt_cls.h b/tools/include/uapi/linux/pkt_cls.h
index 12153771396a..3faee0199a9b 100644
--- a/tools/include/uapi/linux/pkt_cls.h
+++ b/tools/include/uapi/linux/pkt_cls.h
@@ -180,7 +180,7 @@ struct tc_u32_sel {
 
 	short			hoff;
 	__be32			hmask;
-	struct tc_u32_key	keys[0];
+	struct tc_u32_key	keys[];
 };
 
 struct tc_u32_mark {
@@ -192,7 +192,7 @@ struct tc_u32_mark {
 struct tc_u32_pcnt {
 	__u64 rcnt;
 	__u64 rhit;
-	__u64 kcnts[0];
+	__u64 kcnts[];
 };
 
 /* Flags */
diff --git a/tools/include/uapi/linux/seg6.h b/tools/include/uapi/linux/seg6.h
index 286e8d6a8e98..f94baf154c47 100644
--- a/tools/include/uapi/linux/seg6.h
+++ b/tools/include/uapi/linux/seg6.h
@@ -30,7 +30,7 @@ struct ipv6_sr_hdr {
 	__u8	flags;
 	__u16	tag;
 
-	struct in6_addr segments[0];
+	struct in6_addr segments[];
 };
 
 #define SR6_FLAG1_PROTECTED	(1 << 6)
@@ -49,7 +49,7 @@ struct ipv6_sr_hdr {
 struct sr6_tlv {
 	__u8 type;
 	__u8 len;
-	__u8 data[0];
+	__u8 data[];
 };
 
 #endif
diff --git a/tools/include/uapi/linux/usbdevice_fs.h b/tools/include/uapi/linux/usbdevice_fs.h
index cf525cddeb94..74a84e02422a 100644
--- a/tools/include/uapi/linux/usbdevice_fs.h
+++ b/tools/include/uapi/linux/usbdevice_fs.h
@@ -131,7 +131,7 @@ struct usbdevfs_urb {
 	unsigned int signr;	/* signal to be sent on completion,
 				  or 0 if none should be sent. */
 	void __user *usercontext;
-	struct usbdevfs_iso_packet_desc iso_frame_desc[0];
+	struct usbdevfs_iso_packet_desc iso_frame_desc[];
 };
 
 /* ioctls for talking directly to drivers */
@@ -176,7 +176,7 @@ struct usbdevfs_disconnect_claim {
 struct usbdevfs_streams {
 	unsigned int num_streams; /* Not used by USBDEVFS_FREE_STREAMS */
 	unsigned int num_eps;
-	unsigned char eps[0];
+	unsigned char eps[];
 };
 
 /*
diff --git a/tools/include/uapi/sound/asound.h b/tools/include/uapi/sound/asound.h
index 2d3e5df39a59..3974a2a911cc 100644
--- a/tools/include/uapi/sound/asound.h
+++ b/tools/include/uapi/sound/asound.h
@@ -1106,7 +1106,7 @@ struct snd_ctl_elem_value {
 struct snd_ctl_tlv {
 	unsigned int numid;	/* control element numeric identification */
 	unsigned int length;	/* in bytes aligned to 4 */
-	unsigned int tlv[0];	/* first TLV */
+	unsigned int tlv[];	/* first TLV */
 };
 
 #define SNDRV_CTL_IOCTL_PVERSION	_IOR('U', 0x00, int)