1 files changed, 169 insertions, 2 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 437a74a..ba421e6 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -56,6 +56,7 @@
 #include <linux/percpu.h>
 #include <linux/kmemleak.h>
 #include <linux/jump_label.h>
+#include <linux/pfn.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/module.h>
@@ -70,6 +71,26 @@
 #define ARCH_SHF_SMALL 0
 #endif
 
+/*
+ * Modules' sections will be aligned on page boundaries
+ * to ensure complete separation of code and data, but
+ * only when CONFIG_DEBUG_SET_MODULE_RONX=y
+ */
+#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+# define debug_align(X) ALIGN(X, PAGE_SIZE)
+#else
+# define debug_align(X) (X)
+#endif
+
+/*
+ * Given BASE and SIZE this macro calculates the number of pages the
+ * memory regions occupies
+ */
+#define MOD_NUMBER_OF_PAGES(BASE, SIZE) (((SIZE) > 0) ?		\
+		(PFN_DOWN((unsigned long)(BASE) + (SIZE) - 1) -	\
+			 PFN_DOWN((unsigned long)BASE) + 1)	\
+		: (0UL))
+
 /* If this is set, the section belongs in the init part of the module */
 #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
 
@@ -1542,6 +1563,115 @@ static int __unlink_module(void *_mod)
 	return 0;
 }
 
+#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+/*
+ * LKM RO/NX protection: protect module's text/ro-data
+ * from modification and any data from execution.
+ */
+void set_page_attributes(void *start, void *end, int (*set)(unsigned long start, int num_pages))
+{
+	unsigned long begin_pfn = PFN_DOWN((unsigned long)start);
+	unsigned long end_pfn = PFN_DOWN((unsigned long)end);
+
+	if (end_pfn > begin_pfn)
+		set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
+}
+
+static void set_section_ro_nx(void *base,
+			unsigned long text_size,
+			unsigned long ro_size,
+			unsigned long total_size)
+{
+	/* begin and end PFNs of the current subsection */
+	unsigned long begin_pfn;
+	unsigned long end_pfn;
+
+	/*
+	 * Set RO for module text and RO-data:
+	 * - Always protect first page.
+	 * - Do not protect last partial page.
+	 */
+	if (ro_size > 0)
+		set_page_attributes(base, base + ro_size, set_memory_ro);
+
+	/*
+	 * Set NX permissions for module data:
+	 * - Do not protect first partial page.
+	 * - Always protect last page.
+	 */
+	if (total_size > text_size) {
+		begin_pfn = PFN_UP((unsigned long)base + text_size);
+		end_pfn = PFN_UP((unsigned long)base + total_size);
+		if (end_pfn > begin_pfn)
+			set_memory_nx(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
+	}
+}
+
+/* Setting memory back to RW+NX before releasing it */
+void unset_section_ro_nx(struct module *mod, void *module_region)
+{
+	unsigned long total_pages;
+
+	if (mod->module_core == module_region) {
+		/* Set core as NX+RW */
+		total_pages = MOD_NUMBER_OF_PAGES(mod->module_core, mod->core_size);
+		set_memory_nx((unsigned long)mod->module_core, total_pages);
+		set_memory_rw((unsigned long)mod->module_core, total_pages);
+
+	} else if (mod->module_init == module_region) {
+		/* Set init as NX+RW */
+		total_pages = MOD_NUMBER_OF_PAGES(mod->module_init, mod->init_size);
+		set_memory_nx((unsigned long)mod->module_init, total_pages);
+		set_memory_rw((unsigned long)mod->module_init, total_pages);
+	}
+}
+
+/* Iterate through all modules and set each module's text as RW */
+void set_all_modules_text_rw()
+{
+	struct module *mod;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry_rcu(mod, &modules, list) {
+		if ((mod->module_core) && (mod->core_text_size)) {
+			set_page_attributes(mod->module_core,
+						mod->module_core + mod->core_text_size,
+						set_memory_rw);
+		}
+		if ((mod->module_init) && (mod->init_text_size)) {
+			set_page_attributes(mod->module_init,
+						mod->module_init + mod->init_text_size,
+						set_memory_rw);
+		}
+	}
+	mutex_unlock(&module_mutex);
+}
+
+/* Iterate through all modules and set each module's text as RO */
+void set_all_modules_text_ro()
+{
+	struct module *mod;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry_rcu(mod, &modules, list) {
+		if ((mod->module_core) && (mod->core_text_size)) {
+			set_page_attributes(mod->module_core,
+						mod->module_core + mod->core_text_size,
+						set_memory_ro);
+		}
+		if ((mod->module_init) && (mod->init_text_size)) {
+			set_page_attributes(mod->module_init,
+						mod->module_init + mod->init_text_size,
+						set_memory_ro);
+		}
+	}
+	mutex_unlock(&module_mutex);
+}
+#else
+static inline void set_section_ro_nx(void *base, unsigned long text_size, unsigned long ro_size, unsigned long total_size) { }
+static inline void unset_section_ro_nx(struct module *mod, void *module_region) { }
+#endif
+
 /* Free a module, remove from lists, etc. */
 static void free_module(struct module *mod)
 {
@@ -1566,6 +1696,7 @@ static void free_module(struct module *mod)
 	destroy_params(mod->kp, mod->num_kp);
 
 	/* This may be NULL, but that's OK */
+	unset_section_ro_nx(mod, mod->module_init);
 	module_free(mod, mod->module_init);
 	kfree(mod->args);
 	percpu_modfree(mod);
@@ -1574,6 +1705,7 @@ static void free_module(struct module *mod)
 	lockdep_free_key_range(mod->module_core, mod->core_size);
 
 	/* Finally, free the core (containing the module structure) */
+	unset_section_ro_nx(mod, mod->module_core);
 	module_free(mod, mod->module_core);
 
 #ifdef CONFIG_MPU
@@ -1777,8 +1909,19 @@ static void layout_sections(struct module *mod, struct load_info *info)
 			s->sh_entsize = get_offset(mod, &mod->core_size, s, i);
 			DEBUGP("\t%s\n", name);
 		}
-		if (m == 0)
+		switch (m) {
+		case 0: /* executable */
+			mod->core_size = debug_align(mod->core_size);
 			mod->core_text_size = mod->core_size;
+			break;
+		case 1: /* RO: text and ro-data */
+			mod->core_size = debug_align(mod->core_size);
+			mod->core_ro_size = mod->core_size;
+			break;
+		case 3: /* whole core */
+			mod->core_size = debug_align(mod->core_size);
+			break;
+		}
 	}
 
 	DEBUGP("Init section allocation order:\n");
@@ -1796,8 +1939,19 @@ static void layout_sections(struct module *mod, struct load_info *info)
 					 | INIT_OFFSET_MASK);
 			DEBUGP("\t%s\n", sname);
 		}
-		if (m == 0)
+		switch (m) {
+		case 0: /* executable */
+			mod->init_size = debug_align(mod->init_size);
 			mod->init_text_size = mod->init_size;
+			break;
+		case 1: /* RO: text and ro-data */
+			mod->init_size = debug_align(mod->init_size);
+			mod->init_ro_size = mod->init_size;
+			break;
+		case 3: /* whole init */
+			mod->init_size = debug_align(mod->init_size);
+			break;
+		}
 	}
 }
 
@@ -2650,6 +2804,18 @@ static struct module *load_module(void __user *umod,
 	kfree(info.strmap);
 	free_copy(&info);
 
+	/* Set RO and NX regions for core */
+	set_section_ro_nx(mod->module_core,
+				mod->core_text_size,
+				mod->core_ro_size,
+				mod->core_size);
+
+	/* Set RO and NX regions for init */
+	set_section_ro_nx(mod->module_init,
+				mod->init_text_size,
+				mod->init_ro_size,
+				mod->init_size);
+
 	/* Done! */
 	trace_module_load(mod);
 	return mod;
@@ -2753,6 +2919,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	mod->symtab = mod->core_symtab;
 	mod->strtab = mod->core_strtab;
 #endif
+	unset_section_ro_nx(mod, mod->module_init);
 	module_free(mod, mod->module_init);
 	mod->module_init = NULL;
 	mod->init_size = 0;