1 files changed, 170 insertions, 135 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 35ee2c5b7176..a19f1954f4ac 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -28,6 +28,8 @@
 #include <linux/list.h>
 #include <linux/kallsyms.h>
 #include <linux/livepatch.h>
+#include <linux/elf.h>
+#include <linux/moduleloader.h>
 #include <asm/cacheflush.h>
 
 /**
@@ -99,12 +101,12 @@ static void klp_find_object_module(struct klp_object *obj)
 	/*
 	 * We do not want to block removal of patched modules and therefore
 	 * we do not take a reference here. The patches are removed by
-	 * a going module handler instead.
+	 * klp_module_going() instead.
 	 */
 	mod = find_module(obj->name);
 	/*
-	 * Do not mess work of the module coming and going notifiers.
-	 * Note that the patch might still be needed before the going handler
+	 * Do not mess work of klp_module_coming() and klp_module_going().
+	 * Note that the patch might still be needed before klp_module_going()
 	 * is called. Module functions can be called even in the GOING state
 	 * until mod->exit() finishes. This is especially important for
 	 * patches that modify semantic of the functions.
@@ -190,8 +192,8 @@ static int klp_find_object_symbol(const char *objname, const char *name,
 	if (args.addr == 0)
 		pr_err("symbol '%s' not found in symbol table\n", name);
 	else if (args.count > 1 && sympos == 0) {
-		pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n",
-		       args.count, name, objname);
+		pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
+		       name, objname);
 	} else if (sympos != args.count && sympos > 0) {
 		pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
 		       sympos, name, objname ? objname : "vmlinux");
@@ -204,75 +206,109 @@ static int klp_find_object_symbol(const char *objname, const char *name,
 	return -EINVAL;
 }
 
-/*
- * external symbols are located outside the parent object (where the parent
- * object is either vmlinux or the kmod being patched).
- */
-static int klp_find_external_symbol(struct module *pmod, const char *name,
-				    unsigned long *addr)
+static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
 {
-	const struct kernel_symbol *sym;
-
-	/* first, check if it's an exported symbol */
-	preempt_disable();
-	sym = find_symbol(name, NULL, NULL, true, true);
-	if (sym) {
-		*addr = sym->value;
-		preempt_enable();
-		return 0;
-	}
-	preempt_enable();
+	int i, cnt, vmlinux, ret;
+	char objname[MODULE_NAME_LEN];
+	char symname[KSYM_NAME_LEN];
+	char *strtab = pmod->core_kallsyms.strtab;
+	Elf_Rela *relas;
+	Elf_Sym *sym;
+	unsigned long sympos, addr;
 
 	/*
-	 * Check if it's in another .o within the patch module. This also
-	 * checks that the external symbol is unique.
+	 * Since the field widths for objname and symname in the sscanf()
+	 * call are hard-coded and correspond to MODULE_NAME_LEN and
+	 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
+	 * and KSYM_NAME_LEN have the values we expect them to have.
+	 *
+	 * Because the value of MODULE_NAME_LEN can differ among architectures,
+	 * we use the smallest/strictest upper bound possible (56, based on
+	 * the current definition of MODULE_NAME_LEN) to prevent overflows.
 	 */
-	return klp_find_object_symbol(pmod->name, name, 0, addr);
+	BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
+
+	relas = (Elf_Rela *) relasec->sh_addr;
+	/* For each rela in this klp relocation section */
+	for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
+		sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
+		if (sym->st_shndx != SHN_LIVEPATCH) {
+			pr_err("symbol %s is not marked as a livepatch symbol",
+			       strtab + sym->st_name);
+			return -EINVAL;
+		}
+
+		/* Format: .klp.sym.objname.symname,sympos */
+		cnt = sscanf(strtab + sym->st_name,
+			     ".klp.sym.%55[^.].%127[^,],%lu",
+			     objname, symname, &sympos);
+		if (cnt != 3) {
+			pr_err("symbol %s has an incorrectly formatted name",
+			       strtab + sym->st_name);
+			return -EINVAL;
+		}
+
+		/* klp_find_object_symbol() treats a NULL objname as vmlinux */
+		vmlinux = !strcmp(objname, "vmlinux");
+		ret = klp_find_object_symbol(vmlinux ? NULL : objname,
+					     symname, sympos, &addr);
+		if (ret)
+			return ret;
+
+		sym->st_value = addr;
+	}
+
+	return 0;
 }
 
 static int klp_write_object_relocations(struct module *pmod,
 					struct klp_object *obj)
 {
-	int ret = 0;
-	unsigned long val;
-	struct klp_reloc *reloc;
+	int i, cnt, ret = 0;
+	const char *objname, *secname;
+	char sec_objname[MODULE_NAME_LEN];
+	Elf_Shdr *sec;
 
 	if (WARN_ON(!klp_is_object_loaded(obj)))
 		return -EINVAL;
 
-	if (WARN_ON(!obj->relocs))
-		return -EINVAL;
+	objname = klp_is_module(obj) ? obj->name : "vmlinux";
 
 	module_disable_ro(pmod);
+	/* For each klp relocation section */
+	for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
+		sec = pmod->klp_info->sechdrs + i;
+		secname = pmod->klp_info->secstrings + sec->sh_name;
+		if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
+			continue;
 
-	for (reloc = obj->relocs; reloc->name; reloc++) {
-		/* discover the address of the referenced symbol */
-		if (reloc->external) {
-			if (reloc->sympos > 0) {
-				pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n",
-				       reloc->name);
-				ret = -EINVAL;
-				goto out;
-			}
-			ret = klp_find_external_symbol(pmod, reloc->name, &val);
-		} else
-			ret = klp_find_object_symbol(obj->name,
-						     reloc->name,
-						     reloc->sympos,
-						     &val);
+		/*
+		 * Format: .klp.rela.sec_objname.section_name
+		 * See comment in klp_resolve_symbols() for an explanation
+		 * of the selected field width value.
+		 */
+		cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
+		if (cnt != 1) {
+			pr_err("section %s has an incorrectly formatted name",
+			       secname);
+			ret = -EINVAL;
+			break;
+		}
+
+		if (strcmp(objname, sec_objname))
+			continue;
+
+		ret = klp_resolve_symbols(sec, pmod);
 		if (ret)
-			goto out;
+			break;
 
-		ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
-					     val + reloc->addend);
-		if (ret) {
-			pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
-			       reloc->name, val, ret);
-			goto out;
-		}
+		ret = apply_relocate_add(pmod->klp_info->sechdrs,
+					 pmod->core_kallsyms.strtab,
+					 pmod->klp_info->symndx, i, pmod);
+		if (ret)
+			break;
 	}
 
-out:
 	module_enable_ro(pmod);
 	return ret;
 }
@@ -731,11 +767,9 @@ static int klp_init_object_loaded(struct klp_patch *patch,
 	struct klp_func *func;
 	int ret;
 
-	if (obj->relocs) {
-		ret = klp_write_object_relocations(patch->mod, obj);
-		if (ret)
-			return ret;
-	}
+	ret = klp_write_object_relocations(patch->mod, obj);
+	if (ret)
+		return ret;
 
 	klp_for_each_func(obj, func) {
 		ret = klp_find_object_symbol(obj->name, func->old_name,
@@ -870,12 +904,18 @@ int klp_register_patch(struct klp_patch *patch)
 {
 	int ret;
 
-	if (!klp_initialized())
-		return -ENODEV;
-
 	if (!patch || !patch->mod)
 		return -EINVAL;
 
+	if (!is_livepatch_module(patch->mod)) {
+		pr_err("module %s is not marked as a livepatch module",
+		       patch->mod->name);
+		return -EINVAL;
+	}
+
+	if (!klp_initialized())
+		return -ENODEV;
+
 	/*
 	 * A reference is taken on the patch module to prevent it from being
 	 * unloaded.  Right now, we don't allow patch modules to unload since
@@ -894,103 +934,108 @@ int klp_register_patch(struct klp_patch *patch)
 }
 EXPORT_SYMBOL_GPL(klp_register_patch);
 
-static int klp_module_notify_coming(struct klp_patch *patch,
-				     struct klp_object *obj)
+int klp_module_coming(struct module *mod)
 {
-	struct module *pmod = patch->mod;
-	struct module *mod = obj->mod;
 	int ret;
+	struct klp_patch *patch;
+	struct klp_object *obj;
 
-	ret = klp_init_object_loaded(patch, obj);
-	if (ret) {
-		pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
-			pmod->name, mod->name, ret);
-		return ret;
-	}
+	if (WARN_ON(mod->state != MODULE_STATE_COMING))
+		return -EINVAL;
 
-	if (patch->state == KLP_DISABLED)
-		return 0;
+	mutex_lock(&klp_mutex);
+	/*
+	 * Each module has to know that klp_module_coming()
+	 * has been called. We never know what module will
+	 * get patched by a new patch.
+	 */
+	mod->klp_alive = true;
+
+	list_for_each_entry(patch, &klp_patches, list) {
+		klp_for_each_object(patch, obj) {
+			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
+				continue;
 
-	pr_notice("applying patch '%s' to loading module '%s'\n",
-		  pmod->name, mod->name);
+			obj->mod = mod;
 
-	ret = klp_enable_object(obj);
-	if (ret)
-		pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
-			pmod->name, mod->name, ret);
-	return ret;
-}
+			ret = klp_init_object_loaded(patch, obj);
+			if (ret) {
+				pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
+					patch->mod->name, obj->mod->name, ret);
+				goto err;
+			}
 
-static void klp_module_notify_going(struct klp_patch *patch,
-				    struct klp_object *obj)
-{
-	struct module *pmod = patch->mod;
-	struct module *mod = obj->mod;
+			if (patch->state == KLP_DISABLED)
+				break;
 
-	if (patch->state == KLP_DISABLED)
-		goto disabled;
+			pr_notice("applying patch '%s' to loading module '%s'\n",
+				  patch->mod->name, obj->mod->name);
+
+			ret = klp_enable_object(obj);
+			if (ret) {
+				pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
+					patch->mod->name, obj->mod->name, ret);
+				goto err;
+			}
+
+			break;
+		}
+	}
 
-	pr_notice("reverting patch '%s' on unloading module '%s'\n",
-		  pmod->name, mod->name);
+	mutex_unlock(&klp_mutex);
 
-	klp_disable_object(obj);
+	return 0;
 
-disabled:
+err:
+	/*
+	 * If a patch is unsuccessfully applied, return
+	 * error to the module loader.
+	 */
+	pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
+		patch->mod->name, obj->mod->name, obj->mod->name);
+	mod->klp_alive = false;
 	klp_free_object_loaded(obj);
+	mutex_unlock(&klp_mutex);
+
+	return ret;
 }
 
-static int klp_module_notify(struct notifier_block *nb, unsigned long action,
-			     void *data)
+void klp_module_going(struct module *mod)
 {
-	int ret;
-	struct module *mod = data;
 	struct klp_patch *patch;
 	struct klp_object *obj;
 
-	if (action != MODULE_STATE_COMING && action != MODULE_STATE_GOING)
-		return 0;
+	if (WARN_ON(mod->state != MODULE_STATE_GOING &&
+		    mod->state != MODULE_STATE_COMING))
+		return;
 
 	mutex_lock(&klp_mutex);
-
 	/*
-	 * Each module has to know that the notifier has been called.
-	 * We never know what module will get patched by a new patch.
+	 * Each module has to know that klp_module_going()
+	 * has been called. We never know what module will
+	 * get patched by a new patch.
 	 */
-	if (action == MODULE_STATE_COMING)
-		mod->klp_alive = true;
-	else /* MODULE_STATE_GOING */
-		mod->klp_alive = false;
+	mod->klp_alive = false;
 
 	list_for_each_entry(patch, &klp_patches, list) {
 		klp_for_each_object(patch, obj) {
 			if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
 				continue;
 
-			if (action == MODULE_STATE_COMING) {
-				obj->mod = mod;
-				ret = klp_module_notify_coming(patch, obj);
-				if (ret) {
-					obj->mod = NULL;
-					pr_warn("patch '%s' is in an inconsistent state!\n",
-						patch->mod->name);
-				}
-			} else /* MODULE_STATE_GOING */
-				klp_module_notify_going(patch, obj);
+			if (patch->state != KLP_DISABLED) {
+				pr_notice("reverting patch '%s' on unloading module '%s'\n",
+					  patch->mod->name, obj->mod->name);
+				klp_disable_object(obj);
+			}
 
+			klp_free_object_loaded(obj);
 			break;
 		}
 	}
 
 	mutex_unlock(&klp_mutex);
-
-	return 0;
 }
 
-static struct notifier_block klp_module_nb = {
-	.notifier_call = klp_module_notify,
-	.priority = INT_MIN+1, /* called late but before ftrace notifier */
-};
-
 static int __init klp_init(void)
 {
 	int ret;
@@ -1001,21 +1046,11 @@ static int __init klp_init(void)
 		return -EINVAL;
 	}
 
-	ret = register_module_notifier(&klp_module_nb);
-	if (ret)
-		return ret;
-
 	klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
-	if (!klp_root_kobj) {
-		ret = -ENOMEM;
-		goto unregister;
-	}
+	if (!klp_root_kobj)
+		return -ENOMEM;
 
 	return 0;
-
-unregister:
-	unregister_module_notifier(&klp_module_nb);
-	return ret;
 }
 
 module_init(klp_init);