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HID: protect hid_debug_list

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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>
This commit is contained in:
Jiri Kosina 2013-04-16 15:40:09 -07:00
parent a5f04b9df1
commit 2353f2bea3
3 changed files with 8 additions and 0 deletions
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1
drivers/hid/hid-core.c
View File

@ -2319,6 +2319,7 @@ 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);
return hdev;

6
drivers/hid/hid-debug.c
View File

@ -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);
}
@ -990,7 +992,9 @@ 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;
@ -1085,7 +1089,9 @@ 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);

1
include/linux/hid.h
View File

@ -512,6 +512,7 @@ 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;
};