module: clean up load_module a little more.

1fb9341ac34825aa40354e74d9a2c69df7d2c304 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: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 68 insertions, 39 deletions

diff --git a/kernel/module.c b/kernel/module.c
index cc000dd6e4a8..921bed4794e9 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -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));
-                        if (err)
-                                goto free_module;
-                        goto again;
-                }
-                err = -EEXIST;
-                mutex_unlock(&module_mutex);
+        /* Reserve our place in the list. */
+        err = add_unformed_module(mod);
+        if (err)
                 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 @@ again:
 
         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 @@ again:
         /* 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);