path: root/kernel/livepatch/core.c
diff options
authorMinfei Huang <>2015-05-15 10:22:48 +0800
committerJiri Kosina <>2015-05-18 11:08:44 +0200
commit36e505c16e610403c110bab76a95cbfa0436a928 (patch)
tree8fcf5d4dc272250b01926d5d4cb690ee563a60f9 /kernel/livepatch/core.c
parente76ff06a959336fae64b53c36ec60940ca6ef04f (diff)
livepatch: Prevent patch inconsistencies if the coming module notifier fails
The previous patches can be applied, once the corresponding module is loaded. In general, the patch will do relocation (if necessary) and obtain/verify function address before we start to enable patch. There are three different situations in which the coming module notifier can fail: 1) relocations are not applied for some reason. In this case kallsyms for module symbol is not called at all. The patch is not applied to the module. If the user disable and enable patch again, there is possible bug in klp_enable_func. If the user specified func->old_addr for some function in the module (and he shouldn't do that, but nevertheless) our warning would not catch it, ftrace will reject to register the handler because of wrong address or will register the handler for wrong address. 2) relocations are applied successfully, but kallsyms lookup fails. In this case func->old_addr can be correct for all previous lookups, 0 for current failed one, and "unspecified" for the rest. If we undergo the same scenario as in 1, the behaviour differs for three cases, but the patch is not enabled anyway. 3) the object is initialized, but klp_enable_object fails in the notifier due to possible ftrace error. Since it is improbable that ftrace would heal itself in the future, we would get those errors everytime the patch is enabled. In order to fix above situations, we can make obj->mod to NULL, if the coming modified notifier fails. Signed-off-by: Minfei Huang <> Acked-by: Josh Poimboeuf <> Reviewed-by: Miroslav Benes <> Signed-off-by: Jiri Kosina <>
Diffstat (limited to 'kernel/livepatch/core.c')
1 files changed, 18 insertions, 11 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index c5e631cd151b..c03c04637ec6 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -883,7 +883,7 @@ int klp_register_patch(struct klp_patch *patch)
-static void klp_module_notify_coming(struct klp_patch *patch,
+static int klp_module_notify_coming(struct klp_patch *patch,
struct klp_object *obj)
struct module *pmod = patch->mod;
@@ -891,22 +891,23 @@ static void klp_module_notify_coming(struct klp_patch *patch,
int ret;
ret = klp_init_object_loaded(patch, obj);
- if (ret)
- goto err;
+ if (ret) {
+ pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
+ pmod->name, mod->name, ret);
+ return ret;
+ }
if (patch->state == KLP_DISABLED)
- return;
+ return 0;
pr_notice("applying patch '%s' to loading module '%s'\n",
pmod->name, mod->name);
ret = klp_enable_object(obj);
- if (!ret)
- return;
- pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
- pmod->name, mod->name, ret);
+ if (ret)
+ pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
+ pmod->name, mod->name, ret);
+ return ret;
static void klp_module_notify_going(struct klp_patch *patch,
@@ -930,6 +931,7 @@ disabled:
static int klp_module_notify(struct notifier_block *nb, unsigned long action,
void *data)
+ int ret;
struct module *mod = data;
struct klp_patch *patch;
struct klp_object *obj;
@@ -955,7 +957,12 @@ static int klp_module_notify(struct notifier_block *nb, unsigned long action,
if (action == MODULE_STATE_COMING) {
obj->mod = mod;
- klp_module_notify_coming(patch, obj);
+ ret = klp_module_notify_coming(patch, obj);
+ if (ret) {
+ obj->mod = NULL;
+ pr_warn("patch '%s' is in an inconsistent state!\n",
+ patch->mod->name);
+ }
klp_module_notify_going(patch, obj);