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Commit a3535c7e authored by Rusty Russell's avatar Rusty Russell
Browse files

module: clean up load_module a little more. 



1fb9341a made our locking in
load_module more complicated: we grab the mutex once to insert the
module in the list, then again to upgrade it once it's formed.

Since the locking is self-contained, it's neater to do this in
separate functions.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent f2e207f3

kernel/module.c

+68 −39
Original line number Diff line number Diff line
@@ -3145,12 +3145,72 @@ static int may_init_module(void) 
	return 0;

}



/*

 * We try to place it in the list now to make sure it's unique before

 * we dedicate too many resources.  In particular, temporary percpu

 * memory exhaustion.

 */

static int add_unformed_module(struct module *mod)

{

	int err;

	struct module *old;



	mod->state = MODULE_STATE_UNFORMED;



again:

	mutex_lock(&module_mutex);

	if ((old = find_module_all(mod->name, true)) != NULL) {

		if (old->state == MODULE_STATE_COMING

		    || old->state == MODULE_STATE_UNFORMED) {

			/* Wait in case it fails to load. */

			mutex_unlock(&module_mutex);

			err = wait_event_interruptible(module_wq,

					       finished_loading(mod->name));

			if (err)

				goto out_unlocked;

			goto again;

		}

		err = -EEXIST;

		goto out;

	}

	list_add_rcu(&mod->list, &modules);

	err = 0;



out:

	mutex_unlock(&module_mutex);

out_unlocked:

	return err;

}



static int complete_formation(struct module *mod, struct load_info *info)

{

	int err;



	mutex_lock(&module_mutex);



	/* Find duplicate symbols (must be called under lock). */

	err = verify_export_symbols(mod);

	if (err < 0)

		goto out;



	/* This relies on module_mutex for list integrity. */

	module_bug_finalize(info->hdr, info->sechdrs, mod);



	/* Mark state as coming so strong_try_module_get() ignores us,

	 * but kallsyms etc. can see us. */

	mod->state = MODULE_STATE_COMING;



out:

	mutex_unlock(&module_mutex);

	return err;

}



/* Allocate and load the module: note that size of section 0 is always

   zero, and we rely on this for optional sections. */

static int load_module(struct load_info *info, const char __user *uargs,

		       int flags)

{

	struct module *mod, *old;

	struct module *mod;

	long err;



	err = module_sig_check(info);
@@ -3168,31 +3228,10 @@ static int load_module(struct load_info *info, const char __user *uargs, 
		goto free_copy;

	}



	/*

	 * We try to place it in the list now to make sure it's unique

	 * before we dedicate too many resources.  In particular,

	 * temporary percpu memory exhaustion.

	 */

	mod->state = MODULE_STATE_UNFORMED;

again:

	mutex_lock(&module_mutex);

	if ((old = find_module_all(mod->name, true)) != NULL) {

		if (old->state == MODULE_STATE_COMING

		    || old->state == MODULE_STATE_UNFORMED) {

			/* Wait in case it fails to load. */

			mutex_unlock(&module_mutex);

			err = wait_event_interruptible(module_wq,

					       finished_loading(mod->name));

	/* Reserve our place in the list. */

	err = add_unformed_module(mod);

	if (err)

		goto free_module;

			goto again;

		}

		err = -EEXIST;

		mutex_unlock(&module_mutex);

		goto free_module;

	}

	list_add_rcu(&mod->list, &modules);

	mutex_unlock(&module_mutex);



#ifdef CONFIG_MODULE_SIG

	mod->sig_ok = info->sig_ok;
@@ -3245,21 +3284,11 @@ static int load_module(struct load_info *info, const char __user *uargs, 


	dynamic_debug_setup(info->debug, info->num_debug);



	mutex_lock(&module_mutex);

	/* Find duplicate symbols (must be called under lock). */

	err = verify_export_symbols(mod);

	if (err < 0)

	/* Finally it's fully formed, ready to start executing. */

	err = complete_formation(mod, info);

	if (err)

		goto ddebug_cleanup;



	/* This relies on module_mutex for list integrity. */

	module_bug_finalize(info->hdr, info->sechdrs, mod);



	/* Mark state as coming so strong_try_module_get() ignores us,

	 * but kallsyms etc. can see us. */

	mod->state = MODULE_STATE_COMING;



	mutex_unlock(&module_mutex);



	/* Module is ready to execute: parsing args may do that. */

	err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,

			 -32768, 32767, &ddebug_dyndbg_module_param_cb);
@@ -3283,8 +3312,8 @@ static int load_module(struct load_info *info, const char __user *uargs, 
	/* module_bug_cleanup needs module_mutex protection */

	mutex_lock(&module_mutex);

	module_bug_cleanup(mod);

 ddebug_cleanup:

	mutex_unlock(&module_mutex);

 ddebug_cleanup:

	dynamic_debug_remove(info->debug);

	synchronize_sched();

	kfree(mod->args);