[PATCH] livepatch: fix race between enabled_store() and klp_unregister_patch()

Li Bin
2015-11-30T03:56:26Z

There is a potential race as following:

CPU0 | CPU1
-----------------------------|-----------------------------------
enabled_store() | klp_unregister_patch()
| |-mutex_lock(&klp_mutex);
|-mutex_lock(&klp_mutex); | |-klp_free_patch();
| |-mutex_unlock(&klp_mutex);
|-[process the patch's state]|
|-mutex_unlock(&klp_mutex) |

Fix this race condition by adding klp_is_patch_registered() check in
enabled_store() after get the lock klp_mutex.

Signed-off-by: Li Bin <huawei.libin@huawei.com>
---
kernel/livepatch/core.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index db545cb..50af971 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -614,6 +614,11 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,

mutex_lock(&klp_mutex);

+ if (!klp_is_patch_registered(patch)) {
+ ret = -EINVAL;
+ goto err;
+ }
+
if (val == patch->state) {
/* already in requested state */
ret = -EINVAL;
--
1.7.1