From: Jason Baron Jump label uses is_module_text_address() to ensure that the module __init sections are valid before updating them. However, between the check for a valid module __init section and the subsequent jump label update, the module's __init section could be freed out from under us. We fix this potential race by adding a notifier callback to the MODULE_STATE_LIVE state. This notifier is called *after* the __init section has been run but before it is going to be freed. In the callback, the jump label code zeros the key value for any __init jump code within the module, and we add a check for a non-zero key value when we update jump labels. In this way we require no additional data structures. Thanks to Mathieu Desnoyers for pointing out this race condition. Reported-by: Mathieu Desnoyers Cc: Masami Hiramatsu Signed-off-by: Jason Baron LKML-Reference: [ Renamed remove_module_init() to remove_jump_label_module_init() as suggested by Masami Hiramatsu. ] Signed-off-by: Steven Rostedt --- kernel/jump_label.c | 41 ++++++++++++++++++++++++++++++++++++++++- 1 files changed, 40 insertions(+), 1 deletions(-) diff --git a/kernel/jump_label.c b/kernel/jump_label.c index 7be868b..be9e105 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -168,7 +168,8 @@ void jump_label_update(unsigned long key, enum jump_label_type type) count = e_module->nr_entries; iter = e_module->table; while (count--) { - if (kernel_text_address(iter->code)) + if (iter->key && + kernel_text_address(iter->code)) arch_jump_label_transform(iter, type); iter++; } @@ -366,6 +367,39 @@ static void remove_jump_label_module(struct module *mod) } } +static void remove_jump_label_module_init(struct module *mod) +{ + struct hlist_head *head; + struct hlist_node *node, *node_next, *module_node, *module_node_next; + struct jump_label_entry *e; + struct jump_label_module_entry *e_module; + struct jump_entry *iter; + int i, count; + + /* if the module doesn't have jump label entries, just return */ + if (!mod->num_jump_entries) + return; + + for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) { + head = &jump_label_table[i]; + hlist_for_each_entry_safe(e, node, node_next, head, hlist) { + hlist_for_each_entry_safe(e_module, module_node, + module_node_next, + &(e->modules), hlist) { + if (e_module->mod != mod) + continue; + count = e_module->nr_entries; + iter = e_module->table; + while (count--) { + if (within_module_init(iter->code, mod)) + iter->key = 0; + iter++; + } + } + } + } +} + static int jump_label_module_notify(struct notifier_block *self, unsigned long val, void *data) @@ -386,6 +420,11 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val, remove_jump_label_module(mod); mutex_unlock(&jump_label_mutex); break; + case MODULE_STATE_LIVE: + mutex_lock(&jump_label_mutex); + remove_jump_label_module_init(mod); + mutex_unlock(&jump_label_mutex); + break; } return ret; } -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/