HID: protect hid_debug_list
Accesses to hid_device->hid_debug_list are not serialized properly, which
could result in SMP concurrency issues when HID debugfs events are accessesed
by multiple userspace processess.
Serialize all the list operations by a mutex.
Spotted by Al Viro.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index f86dd97..e7765ed 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2319,6 +2319,7 @@
init_waitqueue_head(&hdev->debug_wait);
INIT_LIST_HEAD(&hdev->debug_list);
+ mutex_init(&hdev->debug_list_lock);
sema_init(&hdev->driver_lock, 1);
return hdev;
diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 094cbcf..7e56cb3 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -580,12 +580,14 @@
int i;
struct hid_debug_list *list;
+ mutex_lock(&hdev->debug_list_lock);
list_for_each_entry(list, &hdev->debug_list, node) {
for (i = 0; i < strlen(buf); i++)
list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] =
buf[i];
list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE;
}
+ mutex_unlock(&hdev->debug_list_lock);
wake_up_interruptible(&hdev->debug_wait);
}
@@ -990,7 +992,9 @@
file->private_data = list;
mutex_init(&list->read_mutex);
+ mutex_lock(&list->hdev->debug_list_lock);
list_add_tail(&list->node, &list->hdev->debug_list);
+ mutex_unlock(&list->hdev->debug_list_lock);
out:
return err;
@@ -1085,7 +1089,9 @@
{
struct hid_debug_list *list = file->private_data;
+ mutex_lock(&list->hdev->debug_list_lock);
list_del(&list->node);
+ mutex_unlock(&list->hdev->debug_list_lock);
kfree(list->hid_debug_buf);
kfree(list);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index e14b465..06579c7 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -512,6 +512,7 @@
struct dentry *debug_rdesc;
struct dentry *debug_events;
struct list_head debug_list;
+ struct mutex debug_list_lock;
wait_queue_head_t debug_wait;
};