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>

1 files changed, 5 insertions, 5 deletions

diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
index 17e02b64ea2e..73516e263627 100644
--- a/include/uapi/linux/ndctl.h
+++ b/include/uapi/linux/ndctl.h
@@ -30,25 +30,25 @@ struct nd_cmd_get_config_data_hdr {
 	__u32 in_offset;
 	__u32 in_length;
 	__u32 status;
-	__u8 out_buf[0];
+	__u8 out_buf[];
 } __packed;
 
 struct nd_cmd_set_config_hdr {
 	__u32 in_offset;
 	__u32 in_length;
-	__u8 in_buf[0];
+	__u8 in_buf[];
 } __packed;
 
 struct nd_cmd_vendor_hdr {
 	__u32 opcode;
 	__u32 in_length;
-	__u8 in_buf[0];
+	__u8 in_buf[];
 } __packed;
 
 struct nd_cmd_vendor_tail {
 	__u32 status;
 	__u32 out_length;
-	__u8 out_buf[0];
+	__u8 out_buf[];
 } __packed;
 
 struct nd_cmd_ars_cap {
@@ -86,7 +86,7 @@ struct nd_cmd_ars_status {
 		__u32 reserved;
 		__u64 err_address;
 		__u64 length;
-	} __packed records[0];
+	} __packed records[];
 } __packed;
 
 struct nd_cmd_clear_error {