module: Fix locking in symbol_put_addr()

[karo-tx-linux.git] / kernel / module.c

diff --git a/kernel/module.c b/kernel/module.c
index 4d2b82e610e2a48f429a700f0529d6dc5942700a..8f051a106676fb8f2d5457a9104340cce81ce37a 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -602,13 +602,16 @@ const struct kernel_symbol *find_symbol(const char *name,
 }
 EXPORT_SYMBOL_GPL(find_symbol);
 
-/* Search for module by name: must hold module_mutex. */
+/*
+ * Search for module by name: must hold module_mutex (or preempt disabled
+ * for read-only access).
+ */
 static struct module *find_module_all(const char *name, size_t len,
                                      bool even_unformed)
 {
        struct module *mod;
 
-       module_assert_mutex();
+       module_assert_mutex_or_preempt();
 
        list_for_each_entry(mod, &modules, list) {
                if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)
@@ -621,6 +624,7 @@ static struct module *find_module_all(const char *name, size_t len,
 
 struct module *find_module(const char *name)
 {
+       module_assert_mutex();
        return find_module_all(name, strlen(name), false);
 }
 EXPORT_SYMBOL_GPL(find_module);
@@ -1059,11 +1063,15 @@ void symbol_put_addr(void *addr)
        if (core_kernel_text(a))
                return;
 
-       /* module_text_address is safe here: we're supposed to have reference
-        * to module from symbol_get, so it can't go away. */
+       /*
+        * Even though we hold a reference on the module; we still need to
+        * disable preemption in order to safely traverse the data structure.
+        */
+       preempt_disable();
        modaddr = __module_text_address(a);
        BUG_ON(!modaddr);
        module_put(modaddr);
+       preempt_enable();
 }
 EXPORT_SYMBOL_GPL(symbol_put_addr);