Commit 3bafeb62 authored by Linus Torvalds's avatar Linus Torvalds Committed by Rusty Russell

module: move find_module check to end

I think Rusty may have made the lock a bit _too_ finegrained there, and
didn't add it to some places that needed it. It looks, for example, like
PATCH 1/2 actually drops the lock in places where it's needed
("find_module()" is documented to need it, but now load_module() didn't
hold it at all when it did the find_module()).

Rather than adding a new "module_loading" list, I think we should be able
to just use the existing "modules" list, and just fix up the locking a
bit.

In fact, maybe we could just move the "look up existing module" a bit
later - optimistically assuming that the module doesn't exist, and then
just undoing the work if it turns out that we were wrong, just before
adding ourselves to the list.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 75676500
......@@ -2226,11 +2226,6 @@ 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. */
......@@ -2509,6 +2504,12 @@ static noinline struct module *load_module(void __user *umod,
* The mutex protects against concurrent writers.
*/
mutex_lock(&module_mutex);
if (find_module(mod->name)) {
err = -EEXIST;
/* This will also unlock the mutex */
goto already_exists;
}
list_add_rcu(&mod->list, &modules);
mutex_unlock(&module_mutex);
......@@ -2535,6 +2536,7 @@ static noinline struct module *load_module(void __user *umod,
mutex_lock(&module_mutex);
/* Unlink carefully: kallsyms could be walking list. */
list_del_rcu(&mod->list);
already_exists:
mutex_unlock(&module_mutex);
synchronize_sched();
module_arch_cleanup(mod);
......
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