proc: fold kmalloc() + strcpy() into kmemdup()

strcpy() will recalculate string length second time which is
unnecessary in this case.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Link: https://lore.kernel.org/r/90af27c1-0b86-47a6-a6c8-61a58b8aa747@p183
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Alexey Dobriyan

fs/proc/generic.c

@@ -464,9 +464,9 @@ struct proc_dir_entry *proc_symlink(const char *name,
 			  (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);
 
 	if (ent) {
-		ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
+		ent->size = strlen(dest);
+		ent->data = kmemdup(dest, ent->size + 1, GFP_KERNEL);
 		if (ent->data) {
-			strcpy((char*)ent->data,dest);
 			ent->proc_iops = &proc_link_inode_operations;
 			ent = proc_register(parent, ent);
 		} else {