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head/emulators/xen-kernel47/files/xsa227.patch
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From fa7268b94f8a0a7792ee12d5b8e23a60e52a3a84 Mon Sep 17 00:00:00 2001 | |||||
From: Andrew Cooper <andrew.cooper3@citrix.com> | |||||
Date: Tue, 20 Jun 2017 19:18:54 +0100 | |||||
Subject: [PATCH] x86/grant: Disallow misaligned PTEs | |||||
Pagetable entries must be aligned to function correctly. Disallow attempts | |||||
from the guest to have a grant PTE created at a misaligned address, which | |||||
would result in corruption of the L1 table with largely-guest-controlled | |||||
values. | |||||
This is XSA-227 | |||||
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> | |||||
Reviewed-by: Jan Beulich <jbeulich@suse.com> | |||||
--- | |||||
xen/arch/x86/mm.c | 13 +++++++++++++ | |||||
1 file changed, 13 insertions(+) | |||||
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c | |||||
index 97b3b4b..00f517a 100644 | |||||
--- a/xen/arch/x86/mm.c | |||||
+++ b/xen/arch/x86/mm.c | |||||
@@ -3763,6 +3763,9 @@ static int create_grant_pte_mapping( | |||||
l1_pgentry_t ol1e; | |||||
struct domain *d = v->domain; | |||||
+ if ( !IS_ALIGNED(pte_addr, sizeof(nl1e)) ) | |||||
+ return GNTST_general_error; | |||||
+ | |||||
adjust_guest_l1e(nl1e, d); | |||||
gmfn = pte_addr >> PAGE_SHIFT; | |||||
@@ -3819,6 +3822,16 @@ static int destroy_grant_pte_mapping( | |||||
struct page_info *page; | |||||
l1_pgentry_t ol1e; | |||||
+ /* | |||||
+ * addr comes from Xen's active_entry tracking so isn't guest controlled, | |||||
+ * but it had still better be PTE-aligned. | |||||
+ */ | |||||
+ if ( !IS_ALIGNED(addr, sizeof(ol1e)) ) | |||||
+ { | |||||
+ ASSERT_UNREACHABLE(); | |||||
+ return GNTST_general_error; | |||||
+ } | |||||
+ | |||||
gmfn = addr >> PAGE_SHIFT; | |||||
page = get_page_from_gfn(d, gmfn, NULL, P2M_ALLOC); | |||||
-- | |||||
2.1.4 | |||||