> +static int inotify_ignore(struct inotify_device *dev, s32 wd)
> +{
> + struct inotify_watch *watch;
> + struct inode *inode;
> +
> + down(&dev->sem);
> + watch = idr_find(&dev->idr, wd);
> + if (unlikely(!watch)) {
> + up(&dev->sem);
> + return -EINVAL;
> + }
> + get_inotify_watch(watch);
> + up(&dev->sem);
> +
> + inode = watch->inode;
> + down(&inode->inotify_sem);
> + down(&dev->sem);
> + remove_watch(watch, dev);
> + up(&dev->sem);
> + up(&inode->inotify_sem);
> + put_inotify_watch(watch);
> +
> + return 0;
> +}
So what happens if
* something is holding inotify_sem right now
* ten threads call that on the same watch
* all of them get to down(&inode->inotify_sem); and block there,
having acquired ten references to the watch
* after whatever had been holding ->inotify_sem in the first place
releases it, they will one by one go through the rest of function. And
drop _20_ references to the watch. 9 of those - after we kfree() the
watch...
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