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author | Jason Baron <jbaron@redhat.com> | 2010-10-01 17:23:41 -0400 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2010-10-28 09:17:02 -0400 |
commit | b842f8faf6c7dc2005c6a70631c1a91bac02f180 (patch) | |
tree | fa4c5ed7136be2e39b728173fcae2385b119bcef /kernel/jump_label.c | |
parent | e3e1288e86a07cdeb0aee5860a2dff111c6eff79 (diff) | |
download | op-kernel-dev-b842f8faf6c7dc2005c6a70631c1a91bac02f180.zip op-kernel-dev-b842f8faf6c7dc2005c6a70631c1a91bac02f180.tar.gz |
jump label: Fix module __init section race
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 <mathieu.desnoyers@efficios.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <c6f037b7598777668025ceedd9294212fd95fa34.1285965957.git.jbaron@redhat.com>
[ Renamed remove_module_init() to remove_jump_label_module_init()
as suggested by Masami Hiramatsu. ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/jump_label.c')
-rw-r--r-- | 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; } |