diff options
| -rw-r--r-- | arch/x86/Kconfig.debug | 11 | ||||
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 3 | ||||
| -rw-r--r-- | include/linux/module.h | 11 | ||||
| -rw-r--r-- | kernel/module.c | 171 |
4 files changed, 193 insertions, 3 deletions
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index b59ee76..45143bb 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 3afb33f..2984486 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 b29e745..ddaa689 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 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; |
