From:   Aaron Tomlin <atomlin@redhat.com>
To:     mcgrof@kernel.org
Cc:     cl@linux.com, pmladek@suse.com, mbenes@suse.cz,
        akpm@linux-foundation.org, jeyu@kernel.org,
        linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org,
        atomlin@atomlin.com, ghalat@redhat.com
Subject: [RFC PATCH 06/12] module: Move strict rwx support to a separate file
Date:   Tue, 28 Dec 2021 21:30:35 +0000
Message-Id: <20211228213041.1356334-7-atomlin@redhat.com>
In-Reply-To: <20211228213041.1356334-1-atomlin@redhat.com>
References: <YbKUUJUtjBk/n913@bombadil.infradead.org>
 <20211228213041.1356334-1-atomlin@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

No functional change.

This patch migrates code that makes module text
and rodata memory read-only and non-text memory
non-executable from core module code into
kernel/module/strict_rwx.c.

Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
---
 include/linux/module.h     | 18 ++++++++
 kernel/module/Makefile     |  1 +
 kernel/module/main.c       | 84 --------------------------------------
 kernel/module/strict_rwx.c | 83 +++++++++++++++++++++++++++++++++++++
 4 files changed, 102 insertions(+), 84 deletions(-)
 create mode 100644 kernel/module/strict_rwx.c

diff --git a/include/linux/module.h b/include/linux/module.h
index caa7212cf754..218ac6768433 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -354,6 +354,24 @@ extern void module_enable_x(const struct module *mod);
 static void module_enable_x(const struct module *mod) { }
 #endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
 
+#ifdef CONFIG_STRICT_MODULE_RWX
+extern void frob_rodata(const struct module_layout *layout, int (*set_memory)(unsigned long start, int num_pages));
+extern void frob_ro_after_init(const struct module_layout *layout, int (*set_memory)(unsigned long start, int num_pages));
+extern void frob_writable_data(const struct module_layout *layout, int (*set_memory)(unsigned long start, int num_pages));
+extern void module_enable_ro(const struct module *mod, bool after_init);
+extern void module_enable_nx(const struct module *mod);
+extern int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod);
+
+#else /* !CONFIG_STRICT_MODULE_RWX */
+static void module_enable_nx(const struct module *mod) { }
+static void module_enable_ro(const struct module *mod, bool after_init) {}
+static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
+				       char *secstrings, struct module *mod)
+{
+	return 0;
+}
+#endif /* CONFIG_STRICT_MODULE_RWX */
+
 #ifdef CONFIG_MODULES_TREE_LOOKUP
 struct mod_tree_root {
 	struct latch_tree_root root;
diff --git a/kernel/module/Makefile b/kernel/module/Makefile
index 95fad95a0549..795fe10ac530 100644
--- a/kernel/module/Makefile
+++ b/kernel/module/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_MODULE_SIG_FORMAT) += signature.o
 obj-$(CONFIG_LIVEPATCH) += livepatch.o
 obj-$(CONFIG_MODULES_TREE_LOOKUP) += tree_lookup.o
 obj-$(CONFIG_ARCH_HAS_STRICT_MODULE_RWX) += arch_strict_rwx.o
+obj-$(CONFIG_STRICT_MODULE_RWX) += strict_rwx.o
diff --git a/kernel/module/main.c b/kernel/module/main.c
index a0619256b343..c404d00f7958 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1774,90 +1774,6 @@ static void mod_sysfs_teardown(struct module *mod)
 	mod_sysfs_fini(mod);
 }
 
-#ifdef CONFIG_STRICT_MODULE_RWX
-static void frob_rodata(const struct module_layout *layout,
-			int (*set_memory)(unsigned long start, int num_pages))
-{
-	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
-	set_memory((unsigned long)layout->base + layout->text_size,
-		   (layout->ro_size - layout->text_size) >> PAGE_SHIFT);
-}
-
-static void frob_ro_after_init(const struct module_layout *layout,
-				int (*set_memory)(unsigned long start, int num_pages))
-{
-	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
-	set_memory((unsigned long)layout->base + layout->ro_size,
-		   (layout->ro_after_init_size - layout->ro_size) >> PAGE_SHIFT);
-}
-
-static void frob_writable_data(const struct module_layout *layout,
-			       int (*set_memory)(unsigned long start, int num_pages))
-{
-	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
-	BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1));
-	set_memory((unsigned long)layout->base + layout->ro_after_init_size,
-		   (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
-}
-
-static void module_enable_ro(const struct module *mod, bool after_init)
-{
-	if (!rodata_enabled)
-		return;
-
-	set_vm_flush_reset_perms(mod->core_layout.base);
-	set_vm_flush_reset_perms(mod->init_layout.base);
-	frob_text(&mod->core_layout, set_memory_ro);
-
-	frob_rodata(&mod->core_layout, set_memory_ro);
-	frob_text(&mod->init_layout, set_memory_ro);
-	frob_rodata(&mod->init_layout, set_memory_ro);
-
-	if (after_init)
-		frob_ro_after_init(&mod->core_layout, set_memory_ro);
-}
-
-static void module_enable_nx(const struct module *mod)
-{
-	frob_rodata(&mod->core_layout, set_memory_nx);
-	frob_ro_after_init(&mod->core_layout, set_memory_nx);
-	frob_writable_data(&mod->core_layout, set_memory_nx);
-	frob_rodata(&mod->init_layout, set_memory_nx);
-	frob_writable_data(&mod->init_layout, set_memory_nx);
-}
-
-static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
-				       char *secstrings, struct module *mod)
-{
-	const unsigned long shf_wx = SHF_WRITE|SHF_EXECINSTR;
-	int i;
-
-	for (i = 0; i < hdr->e_shnum; i++) {
-		if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
-			pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
-				mod->name, secstrings + sechdrs[i].sh_name, i);
-			return -ENOEXEC;
-		}
-	}
-
-	return 0;
-}
-
-#else /* !CONFIG_STRICT_MODULE_RWX */
-static void module_enable_nx(const struct module *mod) { }
-static void module_enable_ro(const struct module *mod, bool after_init) {}
-static int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
-				       char *secstrings, struct module *mod)
-{
-	return 0;
-}
-#endif /*  CONFIG_STRICT_MODULE_RWX */
-
 void __weak module_memfree(void *module_region)
 {
 	/*
diff --git a/kernel/module/strict_rwx.c b/kernel/module/strict_rwx.c
new file mode 100644
index 000000000000..8a513ced02c6
--- /dev/null
+++ b/kernel/module/strict_rwx.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * kernel/module/strict_rwx.c - module strict rwx
+ *
+ * Copyright (C) 2015 Rusty Russell
+ */
+
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+#include <linux/set_memory.h>
+
+void frob_rodata(const struct module_layout *layout,
+			int (*set_memory)(unsigned long start, int num_pages))
+{
+	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
+	BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
+	BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
+	set_memory((unsigned long)layout->base + layout->text_size,
+		   (layout->ro_size - layout->text_size) >> PAGE_SHIFT);
+}
+
+void frob_ro_after_init(const struct module_layout *layout,
+				int (*set_memory)(unsigned long start, int num_pages))
+{
+	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
+	BUG_ON((unsigned long)layout->ro_size & (PAGE_SIZE-1));
+	BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
+	set_memory((unsigned long)layout->base + layout->ro_size,
+		   (layout->ro_after_init_size - layout->ro_size) >> PAGE_SHIFT);
+}
+
+void frob_writable_data(const struct module_layout *layout,
+			       int (*set_memory)(unsigned long start, int num_pages))
+{
+	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
+	BUG_ON((unsigned long)layout->ro_after_init_size & (PAGE_SIZE-1));
+	BUG_ON((unsigned long)layout->size & (PAGE_SIZE-1));
+	set_memory((unsigned long)layout->base + layout->ro_after_init_size,
+		   (layout->size - layout->ro_after_init_size) >> PAGE_SHIFT);
+}
+
+void module_enable_ro(const struct module *mod, bool after_init)
+{
+	if (!rodata_enabled)
+		return;
+
+	set_vm_flush_reset_perms(mod->core_layout.base);
+	set_vm_flush_reset_perms(mod->init_layout.base);
+	frob_text(&mod->core_layout, set_memory_ro);
+
+	frob_rodata(&mod->core_layout, set_memory_ro);
+	frob_text(&mod->init_layout, set_memory_ro);
+	frob_rodata(&mod->init_layout, set_memory_ro);
+
+	if (after_init)
+		frob_ro_after_init(&mod->core_layout, set_memory_ro);
+}
+
+void module_enable_nx(const struct module *mod)
+{
+	frob_rodata(&mod->core_layout, set_memory_nx);
+	frob_ro_after_init(&mod->core_layout, set_memory_nx);
+	frob_writable_data(&mod->core_layout, set_memory_nx);
+	frob_rodata(&mod->init_layout, set_memory_nx);
+	frob_writable_data(&mod->init_layout, set_memory_nx);
+}
+
+int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
+				       char *secstrings, struct module *mod)
+{
+	const unsigned long shf_wx = SHF_WRITE|SHF_EXECINSTR;
+	int i;
+
+	for (i = 0; i < hdr->e_shnum; i++) {
+		if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
+			pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
+				mod->name, secstrings + sechdrs[i].sh_name, i);
+			return -ENOEXEC;
+		}
+	}
+
+	return 0;
+}
-- 
2.31.1