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HID: hiddev: fix race between hiddev_disconnect and hiddev_release

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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>
This commit is contained in:
Jiri Kosina 2011-05-20 10:50:13 +02:00
parent 437f3b199c
commit 6cb4b04079
1 changed files with 8 additions and 2 deletions
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10
drivers/hid/usbhid/hiddev.c
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@ -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);
}