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HID: hiddev: fix race between hiddev_disconnect and hiddev_release

When hiddev_disconnect() runs with chardev open, it will proceed with
usbhid_close(). When userspace in parallel runs the hiddev_release(),
it sees !hiddev->exists (as it has been already set so by
hiddev_disconnect()) and kfrees hiddev while hiddev_disconnect() hasn't
finished yet.

Serialize the access to hiddev->exists and hiddev->open by existancelock.

Reported-by: mike-@cinci.rr.com
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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1 parent 437f3b1 commit 6cb4b040795c555c7ab4b1ba29b0dba2b5a42beb Jiri Kosina committed May 20, 2011
Showing with 8 additions and 2 deletions.
  1. +8 −2 drivers/hid/usbhid/hiddev.c
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10 drivers/hid/usbhid/hiddev.c
@@ -242,6 +242,7 @@ static int hiddev_release(struct inode * inode, struct file * file)
list_del(&list->node);
spin_unlock_irqrestore(&list->hiddev->list_lock, flags);
+ mutex_lock(&list->hiddev->existancelock);
if (!--list->hiddev->open) {
if (list->hiddev->exist) {
usbhid_close(list->hiddev->hid);
@@ -252,6 +253,7 @@ static int hiddev_release(struct inode * inode, struct file * file)
}
kfree(list);
+ mutex_unlock(&list->hiddev->existancelock);
return 0;
}
@@ -300,17 +302,21 @@ static int hiddev_open(struct inode *inode, struct file *file)
list_add_tail(&list->node, &hiddev->list);
spin_unlock_irq(&list->hiddev->list_lock);
+ mutex_lock(&hiddev->existancelock);
if (!list->hiddev->open++)
if (list->hiddev->exist) {
struct hid_device *hid = hiddev->hid;
res = usbhid_get_power(hid);
if (res < 0) {
res = -EIO;
- goto bail;
+ goto bail_unlock;
}
usbhid_open(hid);
}
+ mutex_unlock(&hiddev->existancelock);
return 0;
+bail_unlock:
+ mutex_unlock(&hiddev->existancelock);
bail:
file->private_data = NULL;
kfree(list);
@@ -911,7 +917,6 @@ void hiddev_disconnect(struct hid_device *hid)
mutex_lock(&hiddev->existancelock);
hiddev->exist = 0;
- mutex_unlock(&hiddev->existancelock);
usb_deregister_dev(usbhid->intf, &hiddev_class);
@@ -921,4 +926,5 @@ void hiddev_disconnect(struct hid_device *hid)
} else {
kfree(hiddev);
}
+ mutex_unlock(&hiddev->existancelock);
}

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