kbuild: Do modversions checks on module structure

Checks the module structure itself when CONFIG_MODVERSIONS is set.

kernel/module.c

@@ -771,6 +771,18 @@ static int check_version(Elf_Shdr *sechdrs,
 	return 1;
 }
 
+static inline int check_modstruct_version(Elf_Shdr *sechdrs,
+					  unsigned int versindex,
+					  struct module *mod)
+{
+	unsigned int i;
+	struct kernel_symbol_group *ksg;
+
+	if (!__find_symbol("struct_module", &ksg, &i, 1))
+		BUG();
+	return check_version(sechdrs, versindex, "struct_module", mod, ksg, i);
+}
+
 /* First part is kernel version, which we ignore. */
 static inline int same_magic(const char *amagic, const char *bmagic)
 {
@@ -789,6 +801,13 @@ static inline int check_version(Elf_Shdr *sechdrs,
 	return 1;
 }
 
+static inline int check_modstruct_version(Elf_Shdr *sechdrs,
+					  unsigned int versindex,
+					  struct module *mod)
+{
+	return 1;
+}
+
 static inline int same_magic(const char *amagic, const char *bmagic)
 {
 	return strcmp(amagic, bmagic) == 0;
@@ -1185,6 +1204,12 @@ static struct module *load_module(void *umod,
 	}
 	mod = (void *)sechdrs[modindex].sh_addr;
 
+	/* Check module struct version now, before we try to use module. */
+	if (!check_modstruct_version(sechdrs, versindex, mod)) {
+		err = -ENOEXEC;
+		goto free_hdr;
+	}
+
 	/* This is allowed: modprobe --force will invalidate it. */
 	if (!vmagindex) {
 		tainted |= TAINT_FORCED_MODULE;
@@ -1630,3 +1655,9 @@ static int __init symbols_init(void)
 }
 
 __initcall(symbols_init);
+
+#ifdef CONFIG_MODVERSIONS
+/* Generate the signature for struct module here, too, for modversions. */
+void struct_module(struct module *mod) { return; }
+EXPORT_SYMBOL(struct_module);
+#endif

scripts/modpost.c

@@ -308,6 +308,7 @@ read_symbols(char *modname)
 	const char *symname;
 	struct module *mod;
 	struct elf_info info = { };
+	struct symbol *s;
 	Elf_Sym *sym;
 
 	/* When there's no vmlinux, don't print warnings about
@@ -326,6 +327,17 @@ read_symbols(char *modname)
 		handle_moddevtable(mod, &info, sym, symname);
 	}
 	parse_elf_finish(&info);
+
+	/* Our trick to get versioning for struct_module - it's
+	 * never passed as an argument to an exported function, so
+	 * the automatic versioning doesn't pick it up, but it's really
+	 * important anyhow */
+	if (modversions) {
+		s = alloc_symbol("struct_module");
+		/* add to list */
+		s->next = mod->unres;
+		mod->unres = s;
+	}
 }
 
 #define SZ 500
@@ -502,6 +514,7 @@ main(int argc, char **argv)
 {
 	struct module *mod;
 	struct buffer buf = { };
+	struct symbol *s;
 	char fname[SZ];
 
 	for (; argv[1]; argv++) {