From: David Hildenbrand Date: Thu, 14 Mar 2019 16:02:56 +0000 (+0100) Subject: xen/balloon: Fix mapping PG_offline pages to user space X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=0266def913771e718fd0c998eecb072e0685e2c9;p=openwrt%2Fstaging%2Fblogic.git xen/balloon: Fix mapping PG_offline pages to user space The XEN balloon driver - in contrast to other balloon drivers - allows to map some inflated pages to user space. Such pages are allocated via alloc_xenballooned_pages() and freed via free_xenballooned_pages(). The pfn space of these allocated pages is used to map other things by the hypervisor using hypercalls. Pages marked with PG_offline must never be mapped to user space (as this page type uses the mapcount field of struct pages). So what we can do is, clear/set PG_offline when allocating/freeing an inflated pages. This way, most inflated pages can be excluded by dumping tools and the "reused for other purpose" balloon pages are correctly not marked as PG_offline. Fixes: 77c4adf6a6df (xen/balloon: mark inflated pages PG_offline) Reported-by: Julien Grall Tested-by: Julien Grall Signed-off-by: David Hildenbrand Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross --- diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 39b229f9e256..d37dd5bb7a8f 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -604,6 +604,7 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages) while (pgno < nr_pages) { page = balloon_retrieve(true); if (page) { + __ClearPageOffline(page); pages[pgno++] = page; #ifdef CONFIG_XEN_HAVE_PVMMU /* @@ -645,8 +646,10 @@ void free_xenballooned_pages(int nr_pages, struct page **pages) mutex_lock(&balloon_mutex); for (i = 0; i < nr_pages; i++) { - if (pages[i]) + if (pages[i]) { + __SetPageOffline(pages[i]); balloon_append(pages[i]); + } } balloon_stats.target_unpopulated -= nr_pages;