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@xxxxxxx>
---
drivers/hid/hid-core.c | 1 +
drivers/hid/hid-debug.c | 6 ++++++
include/linux/hid.h | 1 +
3 files changed, 8 insertions(+)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 1129f49..e3b7123 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2347,6 +2347,7 @@ struct hid_device *hid_allocate_device(void)
init_waitqueue_head(&hdev->debug_wait);
INIT_LIST_HEAD(&hdev->debug_list);
+ mutex_init(&hdev->debug_list_lock);
sema_init(&hdev->driver_lock, 1);
sema_init(&hdev->driver_input_lock, 1);
diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 933fff0..3337261 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -580,12 +580,14 @@ void hid_debug_event(struct hid_device *hdev, char *buf)
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);
}
@@ -960,7 +962,9 @@ static int hid_debug_events_open(struct inode *inode, struct file *file)
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;
@@ -1055,7 +1059,9 @@ static int hid_debug_events_release(struct inode *inode, struct file *file)
{
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 b7b5ff2..af1b86d 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -515,6 +515,7 @@ struct hid_device { /* device report descriptor */
struct dentry *debug_rdesc;
struct dentry *debug_events;
struct list_head debug_list;
+ struct mutex debug_list_lock;
wait_queue_head_t debug_wait;
};
--
Jiri Kosina
SUSE Labs
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