ipc/msg: replace one-element array with flexible array member

Replace the deprecated one-element array with a modern flexible array
member in the struct compat_msgbuf.

There are no binary differences after this conversion.

Link: https://github.com/KSPP/linux/issues/79
Link: https://lkml.kernel.org/r/20240930195824.153648-2-thorsten.blum@linux.dev


Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Cc: "Sun, Jiebin" <jiebin.sun@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

ipc/msg.c

@@ -978,7 +978,7 @@ SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 
 struct compat_msgbuf {
 	compat_long_t mtype;
-	char mtext[1];
+	char mtext[];
 };
 
 long compat_ksys_msgsnd(int msqid, compat_uptr_t msgp,