From 6d4f36c3fecc0a6a0991716199612c81d909316e Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 5 Mar 2019 13:45:58 +0100 Subject: [PATCH] gnttab: set page refcount for copy-on-grant-transfer Commit 5cc77f9098 ("32-on-64: Fix domain address-size clamping, implement"), which introduced this functionality, took care of clearing the old page's PGC_allocated, but failed to set the bit (and install the associated reference) on the newly allocated one. Furthermore the "mfn" local variable was never updated, and hence the wrong MFN was passed to guest_physmap_add_page() (and back to the destination domain) in this case, leading to an IOMMU mapping into an unowned page. Ideally the code would use assign_pages(), but the call to gnttab_prepare_for_transfer() sits in the middle of the actions mirroring that function. This is XSA-284. Signed-off-by: Jan Beulich Acked-by: George Dunlap --- xen/common/grant_table.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index fd099a8f25..db22d6b441 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -2183,6 +2183,8 @@ gnttab_transfer( page->count_info &= ~(PGC_count_mask|PGC_allocated); free_domheap_page(page); page = new_page; + page->count_info = PGC_allocated | 1; + mfn = page_to_mfn(page); } spin_lock(&e->page_alloc_lock); -- 2.30.2