linux-kernel - [RFC PATCH 1/3] module: Split module_enable_rodata

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Message-ID: <737f952790c96a09ad5e51689918b97ef9b29174.1731148254.git.christophe.leroy@csgroup.eu>
Date: Sat,  9 Nov 2024 11:35:35 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Luis Chamberlain <mcgrof@...nel.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Daniel Gomez <da.gomez@...sung.com>,
	Kees Cook <kees@...nel.org>,
	linux-modules@...r.kernel.org
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC PATCH 1/3] module: Split module_enable_rodata_ro()

module_enable_rodata_ro() is called twice, once before module init
to set rodata sections readonly and once after module init to set
rodata_after_init section readonly.

The second time, only the rodata_after_init section needs to be
set to read-only, no need to re-apply it to already set rodata.

Split module_enable_rodata_ro() in two.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 kernel/module/internal.h   |  3 ++-
 kernel/module/main.c       |  4 ++--
 kernel/module/strict_rwx.c | 13 +++++++++----
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index 2ebece8a789f..994f35a779dc 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -322,7 +322,8 @@ static inline struct module *mod_find(unsigned long addr, struct mod_tree_root *
 }
 #endif /* CONFIG_MODULES_TREE_LOOKUP */
 
-int module_enable_rodata_ro(const struct module *mod, bool after_init);
+int module_enable_rodata_ro(const struct module *mod);
+int module_enable_rodata_ro_after_init(const struct module *mod);
 int module_enable_data_nx(const struct module *mod);
 int module_enable_text_rox(const struct module *mod);
 int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 49b9bca9de12..2de4ad7af335 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2581,7 +2581,7 @@ static noinline int do_init_module(struct module *mod)
 	/* Switch to core kallsyms now init is done: kallsyms may be walking! */
 	rcu_assign_pointer(mod->kallsyms, &mod->core_kallsyms);
 #endif
-	ret = module_enable_rodata_ro(mod, true);
+	ret = module_enable_rodata_ro_after_init(mod);
 	if (ret)
 		goto fail_mutex_unlock;
 	mod_tree_remove_init(mod);
@@ -2751,7 +2751,7 @@ static int complete_formation(struct module *mod, struct load_info *info)
 	module_bug_finalize(info->hdr, info->sechdrs, mod);
 	module_cfi_finalize(info->hdr, info->sechdrs, mod);
 
-	err = module_enable_rodata_ro(mod, false);
+	err = module_enable_rodata_ro(mod);
 	if (err)
 		goto out_strict_rwx;
 	err = module_enable_data_nx(mod);
diff --git a/kernel/module/strict_rwx.c b/kernel/module/strict_rwx.c
index c45caa4690e5..f68c59974ae2 100644
--- a/kernel/module/strict_rwx.c
+++ b/kernel/module/strict_rwx.c
@@ -44,7 +44,7 @@ int module_enable_text_rox(const struct module *mod)
 	return 0;
 }
 
-int module_enable_rodata_ro(const struct module *mod, bool after_init)
+int module_enable_rodata_ro(const struct module *mod)
 {
 	int ret;
 
@@ -58,12 +58,17 @@ int module_enable_rodata_ro(const struct module *mod, bool after_init)
 	if (ret)
 		return ret;
 
-	if (after_init)
-		return module_set_memory(mod, MOD_RO_AFTER_INIT, set_memory_ro);
-
 	return 0;
 }
 
+int module_enable_rodata_ro_after_init(const struct module *mod)
+{
+	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX) || !rodata_enabled)
+		return 0;
+
+	return module_set_memory(mod, MOD_RO_AFTER_INIT, set_memory_ro);
+}
+
 int module_enable_data_nx(const struct module *mod)
 {
 	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
-- 
2.44.0