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>

4 files changed, 7 insertions, 7 deletions

diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h
index 76b7c3f6cd0d..c917c53070d5 100644
--- a/include/uapi/linux/usb/audio.h
+++ b/include/uapi/linux/usb/audio.h
@@ -341,7 +341,7 @@ struct uac_feature_unit_descriptor {
 	__u8 bUnitID;
 	__u8 bSourceID;
 	__u8 bControlSize;
-	__u8 bmaControls[0]; /* variable length */
+	__u8 bmaControls[]; /* variable length */
 } __attribute__((packed));
 
 static inline __u8 uac_feature_unit_iFeature(struct uac_feature_unit_descriptor *desc)
diff --git a/include/uapi/linux/usb/cdc.h b/include/uapi/linux/usb/cdc.h
index 6d61550959ef..acf3852bb676 100644
--- a/include/uapi/linux/usb/cdc.h
+++ b/include/uapi/linux/usb/cdc.h
@@ -171,7 +171,7 @@ struct usb_cdc_mdlm_detail_desc {
 
 	/* type is associated with mdlm_desc.bGUID */
 	__u8	bGuidDescriptorType;
-	__u8	bDetailData[0];
+	__u8	bDetailData[];
 } __attribute__ ((packed));
 
 /* "OBEX Control Model Functional Descriptor" */
@@ -379,7 +379,7 @@ struct usb_cdc_ncm_ndp16 {
 	__le32	dwSignature;
 	__le16	wLength;
 	__le16	wNextNdpIndex;
-	struct	usb_cdc_ncm_dpe16 dpe16[0];
+	struct	usb_cdc_ncm_dpe16 dpe16[];
 } __attribute__ ((packed));
 
 /* 32-bit NCM Datagram Pointer Entry */
@@ -395,7 +395,7 @@ struct usb_cdc_ncm_ndp32 {
 	__le16	wReserved6;
 	__le32	dwNextNdpIndex;
 	__le32	dwReserved12;
-	struct	usb_cdc_ncm_dpe32 dpe32[0];
+	struct	usb_cdc_ncm_dpe32 dpe32[];
 } __attribute__ ((packed));
 
 /* CDC NCM subclass 3.2.1 and 3.2.2 */
diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
index 17ce56198c9a..31fcfa084e63 100644
--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -818,7 +818,7 @@ struct usb_key_descriptor {
 
 	__u8  tTKID[3];
 	__u8  bReserved;
-	__u8  bKeyData[0];
+	__u8  bKeyData[];
 } __attribute__((packed));
 
 /*-------------------------------------------------------------------------*/
diff --git a/include/uapi/linux/usb/raw_gadget.h b/include/uapi/linux/usb/raw_gadget.h
index 0be685272eb1..c7d2199134d7 100644
--- a/include/uapi/linux/usb/raw_gadget.h
+++ b/include/uapi/linux/usb/raw_gadget.h
@@ -60,7 +60,7 @@ enum usb_raw_event_type {
 struct usb_raw_event {
 	__u32		type;
 	__u32		length;
-	__u8		data[0];
+	__u8		data[];
 };
 
 #define USB_RAW_IO_FLAGS_ZERO	0x0001
@@ -90,7 +90,7 @@ struct usb_raw_ep_io {
 	__u16		ep;
 	__u16		flags;
 	__u32		length;
-	__u8		data[0];
+	__u8		data[];
 };
 
 /* Maximum number of non-control endpoints in struct usb_raw_eps_info. */