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xen/gntdevt: Fix race condition in gntdev_release()

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commit 30b03d05e07467b8c6ec683ea96b5bffcbcd3931 upstream.

While gntdev_release() is called the MMU notifier is still registered
and can traverse priv->maps list even if no pages are mapped (which is
the case -- gntdev_release() is called after all). But
gntdev_release() will clear that list, so make sure that only one of
those things happens at the same time.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Marek Marczykowski-Górecki
2015-06-26 03:28:24 +02:00
committed by Greg Kroah-Hartman
parent 3f2c206ae6
commit 292f53675e
1 changed files with 2 additions and 0 deletions
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drivers/xen/gntdev.c
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@@ -534,12 +534,14 @@ static int gntdev_release(struct inode *inode, struct file *flip)
pr_debug("priv %p\n", priv);
mutex_lock(&priv->lock);
while (!list_empty(&priv->maps)) {
map = list_entry(priv->maps.next, struct grant_map, next);
list_del(&map->next);
gntdev_put_map(NULL /* already removed */, map);
}
WARN_ON(!list_empty(&priv->freeable_maps));
mutex_unlock(&priv->lock);
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);