1 files changed, 208 insertions, 112 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 0129769..8c6b428 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -72,7 +72,11 @@
 /* If this is set, the section belongs in the init part of the module */
 #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
 
-/* List of modules, protected by module_mutex or preempt_disable
+/*
+ * Mutex protects:
+ * 1) List of modules (also safely readable with preempt_disable),
+ * 2) module_use links,
+ * 3) module_addr_min/module_addr_max.
  * (delete uses stop_machine/add uses RCU list operations). */
 DEFINE_MUTEX(module_mutex);
 EXPORT_SYMBOL_GPL(module_mutex);
@@ -90,7 +94,8 @@ static DECLARE_WAIT_QUEUE_HEAD(module_wq);
 
 static BLOCKING_NOTIFIER_HEAD(module_notify_list);
 
-/* Bounds of module allocation, for speeding __module_address */
+/* Bounds of module allocation, for speeding __module_address.
+ * Protected by module_mutex. */
 static unsigned long module_addr_min = -1UL, module_addr_max = 0;
 
 int register_module_notifier(struct notifier_block * nb)
@@ -329,7 +334,7 @@ static bool find_symbol_in_section(const struct symsearch *syms,
 }
 
 /* Find a symbol and return it, along with, (optional) crc and
- * (optional) module which owns it */
+ * (optional) module which owns it.  Needs preempt disabled or module_mutex. */
 const struct kernel_symbol *find_symbol(const char *name,
 					struct module **owner,
 					const unsigned long **crc,
@@ -523,7 +528,8 @@ static void module_unload_init(struct module *mod)
 {
 	int cpu;
 
-	INIT_LIST_HEAD(&mod->modules_which_use_me);
+	INIT_LIST_HEAD(&mod->source_list);
+	INIT_LIST_HEAD(&mod->target_list);
 	for_each_possible_cpu(cpu) {
 		per_cpu_ptr(mod->refptr, cpu)->incs = 0;
 		per_cpu_ptr(mod->refptr, cpu)->decs = 0;
@@ -535,20 +541,13 @@ static void module_unload_init(struct module *mod)
 	mod->waiter = current;
 }
 
-/* modules using other modules */
-struct module_use
-{
-	struct list_head list;
-	struct module *module_which_uses;
-};
-
 /* Does a already use b? */
 static int already_uses(struct module *a, struct module *b)
 {
 	struct module_use *use;
 
-	list_for_each_entry(use, &b->modules_which_use_me, list) {
-		if (use->module_which_uses == a) {
+	list_for_each_entry(use, &b->source_list, source_list) {
+		if (use->source == a) {
 			DEBUGP("%s uses %s!\n", a->name, b->name);
 			return 1;
 		}
@@ -557,62 +556,68 @@ static int already_uses(struct module *a, struct module *b)
 	return 0;
 }
 
-/* Module a uses b */
-int use_module(struct module *a, struct module *b)
+/*
+ * Module a uses b
+ *  - we add 'a' as a "source", 'b' as a "target" of module use
+ *  - the module_use is added to the list of 'b' sources (so
+ *    'b' can walk the list to see who sourced them), and of 'a'
+ *    targets (so 'a' can see what modules it targets).
+ */
+static int add_module_usage(struct module *a, struct module *b)
 {
 	struct module_use *use;
-	int no_warn, err;
 
-	if (b == NULL || already_uses(a, b)) return 1;
+	DEBUGP("Allocating new usage for %s.\n", a->name);
+	use = kmalloc(sizeof(*use), GFP_ATOMIC);
+	if (!use) {
+		printk(KERN_WARNING "%s: out of memory loading\n", a->name);
+		return -ENOMEM;
+	}
+
+	use->source = a;
+	use->target = b;
+	list_add(&use->source_list, &b->source_list);
+	list_add(&use->target_list, &a->target_list);
+	return 0;
+}
+
+/* Module a uses b: caller needs module_mutex() */
+int ref_module(struct module *a, struct module *b)
+{
+	int err;
 
-	/* If we're interrupted or time out, we fail. */
-	if (wait_event_interruptible_timeout(
-		    module_wq, (err = strong_try_module_get(b)) != -EBUSY,
-		    30 * HZ) <= 0) {
-		printk("%s: gave up waiting for init of module %s.\n",
-		       a->name, b->name);
+	if (b == NULL || already_uses(a, b))
 		return 0;
-	}
 
-	/* If strong_try_module_get() returned a different error, we fail. */
+	/* If module isn't available, we fail. */
+	err = strong_try_module_get(b);
 	if (err)
-		return 0;
+		return err;
 
-	DEBUGP("Allocating new usage for %s.\n", a->name);
-	use = kmalloc(sizeof(*use), GFP_ATOMIC);
-	if (!use) {
-		printk("%s: out of memory loading\n", a->name);
+	err = add_module_usage(a, b);
+	if (err) {
 		module_put(b);
-		return 0;
+		return err;
 	}
-
-	use->module_which_uses = a;
-	list_add(&use->list, &b->modules_which_use_me);
-	no_warn = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
-	return 1;
+	return 0;
 }
-EXPORT_SYMBOL_GPL(use_module);
+EXPORT_SYMBOL_GPL(ref_module);
 
 /* Clear the unload stuff of the module. */
 static void module_unload_free(struct module *mod)
 {
-	struct module *i;
+	struct module_use *use, *tmp;
 
-	list_for_each_entry(i, &modules, list) {
-		struct module_use *use;
-
-		list_for_each_entry(use, &i->modules_which_use_me, list) {
-			if (use->module_which_uses == mod) {
-				DEBUGP("%s unusing %s\n", mod->name, i->name);
-				module_put(i);
-				list_del(&use->list);
-				kfree(use);
-				sysfs_remove_link(i->holders_dir, mod->name);
-				/* There can be at most one match. */
-				break;
-			}
-		}
+	mutex_lock(&module_mutex);
+	list_for_each_entry_safe(use, tmp, &mod->target_list, target_list) {
+		struct module *i = use->target;
+		DEBUGP("%s unusing %s\n", mod->name, i->name);
+		module_put(i);
+		list_del(&use->source_list);
+		list_del(&use->target_list);
+		kfree(use);
 	}
+	mutex_unlock(&module_mutex);
 }
 
 #ifdef CONFIG_MODULE_FORCE_UNLOAD
@@ -735,7 +740,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 		goto out;
 	}
 
-	if (!list_empty(&mod->modules_which_use_me)) {
+	if (!list_empty(&mod->source_list)) {
 		/* Other modules depend on us: get rid of them first. */
 		ret = -EWOULDBLOCK;
 		goto out;
@@ -779,13 +784,14 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_GOING, mod);
 	async_synchronize_full();
-	mutex_lock(&module_mutex);
+
 	/* Store the name of the last unloaded module for diagnostic purposes */
 	strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
 	ddebug_remove_module(mod->name);
-	free_module(mod);
 
- out:
+	free_module(mod);
+	return 0;
+out:
 	mutex_unlock(&module_mutex);
 	return ret;
 }
@@ -799,9 +805,9 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
 
 	/* Always include a trailing , so userspace can differentiate
            between this and the old multi-field proc format. */
-	list_for_each_entry(use, &mod->modules_which_use_me, list) {
+	list_for_each_entry(use, &mod->source_list, source_list) {
 		printed_something = 1;
-		seq_printf(m, "%s,", use->module_which_uses->name);
+		seq_printf(m, "%s,", use->source->name);
 	}
 
 	if (mod->init != NULL && mod->exit == NULL) {
@@ -880,11 +886,11 @@ static inline void module_unload_free(struct module *mod)
 {
 }
 
-int use_module(struct module *a, struct module *b)
+int ref_module(struct module *a, struct module *b)
 {
-	return strong_try_module_get(b) == 0;
+	return strong_try_module_get(b);
 }
-EXPORT_SYMBOL_GPL(use_module);
+EXPORT_SYMBOL_GPL(ref_module);
 
 static inline void module_unload_init(struct module *mod)
 {
@@ -1001,6 +1007,8 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
 {
 	const unsigned long *crc;
 
+	/* Since this should be found in kernel (which can't be removed),
+	 * no locking is necessary. */
 	if (!find_symbol(MODULE_SYMBOL_PREFIX "module_layout", NULL,
 			 &crc, true, false))
 		BUG();
@@ -1043,29 +1051,62 @@ static inline int same_magic(const char *amagic, const char *bmagic,
 }
 #endif /* CONFIG_MODVERSIONS */
 
-/* Resolve a symbol for this module.  I.e. if we find one, record usage.
-   Must be holding module_mutex. */
+/* Resolve a symbol for this module.  I.e. if we find one, record usage. */
 static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
 						  unsigned int versindex,
 						  const char *name,
-						  struct module *mod)
+						  struct module *mod,
+						  char ownername[])
 {
 	struct module *owner;
 	const struct kernel_symbol *sym;
 	const unsigned long *crc;
+	int err;
 
+	mutex_lock(&module_mutex);
 	sym = find_symbol(name, &owner, &crc,
 			  !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
-	/* use_module can fail due to OOM,
-	   or module initialization or unloading */
-	if (sym) {
-		if (!check_version(sechdrs, versindex, name, mod, crc, owner)
-		    || !use_module(mod, owner))
-			sym = NULL;
+	if (!sym)
+		goto unlock;
+
+	if (!check_version(sechdrs, versindex, name, mod, crc, owner)) {
+		sym = ERR_PTR(-EINVAL);
+		goto getname;
+	}
+
+	err = ref_module(mod, owner);
+	if (err) {
+		sym = ERR_PTR(err);
+		goto getname;
 	}
+
+getname:
+	/* We must make copy under the lock if we failed to get ref. */
+	strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
+unlock:
+	mutex_unlock(&module_mutex);
 	return sym;
 }
 
+static const struct kernel_symbol *resolve_symbol_wait(Elf_Shdr *sechdrs,
+						       unsigned int versindex,
+						       const char *name,
+						       struct module *mod)
+{
+	const struct kernel_symbol *ksym;
+	char ownername[MODULE_NAME_LEN];
+
+	if (wait_event_interruptible_timeout(module_wq,
+			!IS_ERR(ksym = resolve_symbol(sechdrs, versindex, name,
+						      mod, ownername)) ||
+			PTR_ERR(ksym) != -EBUSY,
+					     30 * HZ) <= 0) {
+		printk(KERN_WARNING "%s: gave up waiting for init of module %s.\n",
+		       mod->name, ownername);
+	}
+	return ksym;
+}
+
 /*
  * /sys/module/foo/sections stuff
  * J. Corbet <corbet@lwn.net>
@@ -1295,7 +1336,34 @@ static inline void remove_notes_attrs(struct module *mod)
 #endif
 
 #ifdef CONFIG_SYSFS
-int module_add_modinfo_attrs(struct module *mod)
+static void add_usage_links(struct module *mod)
+{
+#ifdef CONFIG_MODULE_UNLOAD
+	struct module_use *use;
+	int nowarn;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry(use, &mod->target_list, target_list) {
+		nowarn = sysfs_create_link(use->target->holders_dir,
+					   &mod->mkobj.kobj, mod->name);
+	}
+	mutex_unlock(&module_mutex);
+#endif
+}
+
+static void del_usage_links(struct module *mod)
+{
+#ifdef CONFIG_MODULE_UNLOAD
+	struct module_use *use;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry(use, &mod->target_list, target_list)
+		sysfs_remove_link(use->target->holders_dir, mod->name);
+	mutex_unlock(&module_mutex);
+#endif
+}
+
+static int module_add_modinfo_attrs(struct module *mod)
 {
 	struct module_attribute *attr;
 	struct module_attribute *temp_attr;
@@ -1321,7 +1389,7 @@ int module_add_modinfo_attrs(struct module *mod)
 	return error;
 }
 
-void module_remove_modinfo_attrs(struct module *mod)
+static void module_remove_modinfo_attrs(struct module *mod)
 {
 	struct module_attribute *attr;
 	int i;
@@ -1337,7 +1405,7 @@ void module_remove_modinfo_attrs(struct module *mod)
 	kfree(mod->modinfo_attrs);
 }
 
-int mod_sysfs_init(struct module *mod)
+static int mod_sysfs_init(struct module *mod)
 {
 	int err;
 	struct kobject *kobj;
@@ -1371,12 +1439,16 @@ out:
 	return err;
 }
 
-int mod_sysfs_setup(struct module *mod,
+static int mod_sysfs_setup(struct module *mod,
 			   struct kernel_param *kparam,
 			   unsigned int num_params)
 {
 	int err;
 
+	err = mod_sysfs_init(mod);
+	if (err)
+		goto out;
+
 	mod->holders_dir = kobject_create_and_add("holders", &mod->mkobj.kobj);
 	if (!mod->holders_dir) {
 		err = -ENOMEM;
@@ -1391,6 +1463,8 @@ int mod_sysfs_setup(struct module *mod,
 	if (err)
 		goto out_unreg_param;
 
+	add_usage_links(mod);
+
 	kobject_uevent(&mod->mkobj.kobj, KOBJ_ADD);
 	return 0;
 
@@ -1400,6 +1474,7 @@ out_unreg_holders:
 	kobject_put(mod->holders_dir);
 out_unreg:
 	kobject_put(&mod->mkobj.kobj);
+out:
 	return err;
 }
 
@@ -1410,14 +1485,40 @@ static void mod_sysfs_fini(struct module *mod)
 
 #else /* CONFIG_SYSFS */
 
+static inline int mod_sysfs_init(struct module *mod)
+{
+	return 0;
+}
+
+static inline int mod_sysfs_setup(struct module *mod,
+			   struct kernel_param *kparam,
+			   unsigned int num_params)
+{
+	return 0;
+}
+
+static inline int module_add_modinfo_attrs(struct module *mod)
+{
+	return 0;
+}
+
+static inline void module_remove_modinfo_attrs(struct module *mod)
+{
+}
+
 static void mod_sysfs_fini(struct module *mod)
 {
 }
 
+static void del_usage_links(struct module *mod)
+{
+}
+
 #endif /* CONFIG_SYSFS */
 
 static void mod_kobject_remove(struct module *mod)
 {
+	del_usage_links(mod);
 	module_remove_modinfo_attrs(mod);
 	module_param_sysfs_remove(mod);
 	kobject_put(mod->mkobj.drivers_dir);
@@ -1436,13 +1537,15 @@ static int __unlink_module(void *_mod)
 	return 0;
 }
 
-/* Free a module, remove from lists, etc (must hold module_mutex). */
+/* Free a module, remove from lists, etc. */
 static void free_module(struct module *mod)
 {
 	trace_module_free(mod);
 
 	/* Delete from various lists */
+	mutex_lock(&module_mutex);
 	stop_machine(__unlink_module, mod, NULL);
+	mutex_unlock(&module_mutex);
 	remove_notes_attrs(mod);
 	remove_sect_attrs(mod);
 	mod_kobject_remove(mod);
@@ -1493,6 +1596,8 @@ EXPORT_SYMBOL_GPL(__symbol_get);
 /*
  * Ensure that an exported symbol [global namespace] does not already exist
  * in the kernel or in some other module's exported symbol table.
+ *
+ * You must hold the module_mutex.
  */
 static int verify_export_symbols(struct module *mod)
 {
@@ -1558,21 +1663,23 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
 			break;
 
 		case SHN_UNDEF:
-			ksym = resolve_symbol(sechdrs, versindex,
-					      strtab + sym[i].st_name, mod);
+			ksym = resolve_symbol_wait(sechdrs, versindex,
+						   strtab + sym[i].st_name,
+						   mod);
 			/* Ok if resolved.  */
-			if (ksym) {
+			if (ksym && !IS_ERR(ksym)) {
 				sym[i].st_value = ksym->value;
 				break;
 			}
 
 			/* Ok if weak.  */
-			if (ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
+			if (!ksym && ELF_ST_BIND(sym[i].st_info) == STB_WEAK)
 				break;
 
-			printk(KERN_WARNING "%s: Unknown symbol %s\n",
-			       mod->name, strtab + sym[i].st_name);
-			ret = -ENOENT;
+			printk(KERN_WARNING "%s: Unknown symbol %s (err %li)\n",
+			       mod->name, strtab + sym[i].st_name,
+			       PTR_ERR(ksym));
+			ret = PTR_ERR(ksym) ?: -ENOENT;
 			break;
 
 		default:
@@ -1960,11 +2067,13 @@ static void *module_alloc_update_bounds(unsigned long size)
 	void *ret = module_alloc(size);
 
 	if (ret) {
+		mutex_lock(&module_mutex);
 		/* Update module bounds. */
 		if ((unsigned long)ret < module_addr_min)
 			module_addr_min = (unsigned long)ret;
 		if ((unsigned long)ret + size > module_addr_max)
 			module_addr_max = (unsigned long)ret + size;
+		mutex_unlock(&module_mutex);
 	}
 	return ret;
 }
@@ -2139,11 +2248,6 @@ static noinline struct module *load_module(void __user *umod,
 		goto free_mod;
 	}
 
-	if (find_module(mod->name)) {
-		err = -EEXIST;
-		goto free_mod;
-	}
-
 	mod->state = MODULE_STATE_COMING;
 
 	/* Allow arches to frob section contents and sizes.  */
@@ -2234,11 +2338,6 @@ static noinline struct module *load_module(void __user *umod,
 	/* Now we've moved module, initialize linked lists, etc. */
 	module_unload_init(mod);
 
-	/* add kobject, so we can reference it. */
-	err = mod_sysfs_init(mod);
-	if (err)
-		goto free_unload;
-
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(sechdrs, infoindex, "license"));
 
@@ -2363,11 +2462,6 @@ static noinline struct module *load_module(void __user *umod,
 			goto cleanup;
 	}
 
-        /* Find duplicate symbols */
-	err = verify_export_symbols(mod);
-	if (err < 0)
-		goto cleanup;
-
   	/* Set up and sort exception table */
 	mod->extable = section_objs(hdr, sechdrs, secstrings, "__ex_table",
 				    sizeof(*mod->extable), &mod->num_exentries);
@@ -2426,7 +2520,19 @@ static noinline struct module *load_module(void __user *umod,
 	 * function to insert in a way safe to concurrent readers.
 	 * The mutex protects against concurrent writers.
 	 */
+	mutex_lock(&module_mutex);
+	if (find_module(mod->name)) {
+		err = -EEXIST;
+		goto unlock;
+	}
+
+	/* Find duplicate symbols */
+	err = verify_export_symbols(mod);
+	if (err < 0)
+		goto unlock;
+
 	list_add_rcu(&mod->list, &modules);
+	mutex_unlock(&module_mutex);
 
 	err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL);
 	if (err < 0)
@@ -2435,6 +2541,7 @@ static noinline struct module *load_module(void __user *umod,
 	err = mod_sysfs_setup(mod, mod->kp, mod->num_kp);
 	if (err < 0)
 		goto unlink;
+
 	add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
 	add_notes_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
 
@@ -2447,15 +2554,15 @@ static noinline struct module *load_module(void __user *umod,
 	return mod;
 
  unlink:
+	mutex_lock(&module_mutex);
 	/* Unlink carefully: kallsyms could be walking list. */
 	list_del_rcu(&mod->list);
+ unlock:
+	mutex_unlock(&module_mutex);
 	synchronize_sched();
 	module_arch_cleanup(mod);
  cleanup:
 	free_modinfo(mod);
-	kobject_del(&mod->mkobj.kobj);
-	kobject_put(&mod->mkobj.kobj);
- free_unload:
 	module_unload_free(mod);
 #if defined(CONFIG_MODULE_UNLOAD)
 	free_percpu(mod->refptr);
@@ -2502,19 +2609,10 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	if (!capable(CAP_SYS_MODULE) || modules_disabled)
 		return -EPERM;
 
-	/* Only one module load at a time, please */
-	if (mutex_lock_interruptible(&module_mutex) != 0)
-		return -EINTR;
-
 	/* Do all the hard work */
 	mod = load_module(umod, len, uargs);
-	if (IS_ERR(mod)) {
-		mutex_unlock(&module_mutex);
+	if (IS_ERR(mod))
 		return PTR_ERR(mod);
-	}
-
-	/* Drop lock so they can recurse */
-	mutex_unlock(&module_mutex);
 
 	blocking_notifier_call_chain(&module_notify_list,
 			MODULE_STATE_COMING, mod);
@@ -2531,9 +2629,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 		module_put(mod);
 		blocking_notifier_call_chain(&module_notify_list,
 					     MODULE_STATE_GOING, mod);
-		mutex_lock(&module_mutex);
 		free_module(mod);
-		mutex_unlock(&module_mutex);
 		wake_up(&module_wq);
 		return ret;
 	}