| From | Ben Hutchings <> | Date | Fri, 09 Oct 2015 01:12:27 +0100 | Subject | [PATCH 3.2 004/107] xen/gntdevt: Fix race condition in gntdev_release() |
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3.2.72-rc1 review patch. If anyone has any objections, please let me know.
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From: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
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> [bwh: Backported to 3.2: - Adjust context - gntdev_priv::lock is a spinlock rather than a mutex. As gntdev_put_map() may sleep, we need to unlock inside the loop.] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -493,11 +493,15 @@ static int gntdev_release(struct inode * pr_debug("priv %p\n", priv); + spin_lock(&priv->lock); while (!list_empty(&priv->maps)) { map = list_entry(priv->maps.next, struct grant_map, next); list_del(&map->next); + spin_unlock(&priv->lock); gntdev_put_map(map); + spin_lock(&priv->lock); } + spin_unlock(&priv->lock); if (use_ptemod) mmu_notifier_unregister(&priv->mn, priv->mm);
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