4 files changed, 193 insertions, 3 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index b59ee765414e..45143bbcfe5e 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -117,6 +117,17 @@ config DEBUG_RODATA_TEST
           feature as well as for the change_page_attr() infrastructure.
           If in doubt, say "N"
 
+config DEBUG_SET_MODULE_RONX
+        bool "Set loadable kernel module data as NX and text as RO"
+        depends on MODULES
+        ---help---
+          This option helps catch unintended modifications to loadable
+          kernel module's text and read-only data. It also prevents execution
+          of module data. Such protection may interfere with run-time code
+          patching and dynamic kernel tracing - and they might also protect
+          against certain classes of kernel exploits.
+          If in doubt, say "N".
+
 config DEBUG_NX_TEST
         tristate "Testcase for the NX non-executable stack feature"
         depends on DEBUG_KERNEL && m
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 3afb33f14d2d..298448656b60 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -19,6 +19,7 @@
 #include <linux/sched.h>
 #include <linux/init.h>
 #include <linux/list.h>
+#include <linux/module.h>
 
 #include <trace/syscall.h>
 
@@ -49,6 +50,7 @@ static DEFINE_PER_CPU(int, save_modifying_code);
 int ftrace_arch_code_modify_prepare(void)
 {
         set_kernel_text_rw();
+        set_all_modules_text_rw();
         modifying_code = 1;
         return 0;
 }
@@ -56,6 +58,7 @@ int ftrace_arch_code_modify_prepare(void)
 int ftrace_arch_code_modify_post_process(void)
 {
         modifying_code = 0;
+        set_all_modules_text_ro();
         set_kernel_text_ro();
         return 0;
 }
diff --git a/include/linux/module.h b/include/linux/module.h
index b29e7458b966..ddaa689d71bd 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -308,6 +308,9 @@ struct module
         /* The size of the executable code in each section.  */
         unsigned int init_text_size, core_text_size;
 
+        /* Size of RO sections of the module (text+rodata) */
+        unsigned int init_ro_size, core_ro_size;
+
         /* Arch-specific module values */
         struct mod_arch_specific arch;
 
@@ -672,7 +675,6 @@ static inline int module_get_iter_tracepoints(struct tracepoint_iter *iter)
 {
         return 0;
 }
-
 #endif /* CONFIG_MODULES */
 
 #ifdef CONFIG_SYSFS
@@ -687,6 +689,13 @@ extern int module_sysfs_initialized;
 
 #define __MODULE_STRING(x) __stringify(x)
 
+#ifdef CONFIG_DEBUG_SET_MODULE_RONX
+extern void set_all_modules_text_rw(void);
+extern void set_all_modules_text_ro(void);
+#else
+static inline void set_all_modules_text_rw(void) { }
+static inline void set_all_modules_text_ro(void) { }
+#endif
 
 #ifdef CONFIG_GENERIC_BUG
 void module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *,
diff --git a/kernel/module.c b/kernel/module.c
index 437a74a7524a..ba421e6b4ada 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;