diff options
Diffstat (limited to 'system/xen/xsa/xsa299-4.12-0009-x86-mm-Properly-handle-linear-pagetable-promotion-fa.patch')
| -rw-r--r-- | system/xen/xsa/xsa299-4.12-0009-x86-mm-Properly-handle-linear-pagetable-promotion-fa.patch | 106 |
1 files changed, 0 insertions, 106 deletions
diff --git a/system/xen/xsa/xsa299-4.12-0009-x86-mm-Properly-handle-linear-pagetable-promotion-fa.patch b/system/xen/xsa/xsa299-4.12-0009-x86-mm-Properly-handle-linear-pagetable-promotion-fa.patch deleted file mode 100644 index bbaba794fc..0000000000 --- a/system/xen/xsa/xsa299-4.12-0009-x86-mm-Properly-handle-linear-pagetable-promotion-fa.patch +++ /dev/null @@ -1,106 +0,0 @@ -From da3d1d258e54fe600f7f75287183b74d957ec63b Mon Sep 17 00:00:00 2001 -From: George Dunlap <george.dunlap@citrix.com> -Date: Thu, 10 Oct 2019 17:57:49 +0100 -Subject: [PATCH 09/11] x86/mm: Properly handle linear pagetable promotion - failures - -In order to allow recursive pagetable promotions and demotions to be -interrupted, Xen must keep track of the state of the sub-pages -promoted or demoted. This is stored in two elements in the page -struct: nr_entries_validated and partial_flags. - -The rule is that entries [0, nr_entries_validated) should always be -validated and hold a general reference count. If partial_flags is -zero, then [nr_entries_validated] is not validated and no reference -count is held. If PTF_partial_set is set, then [nr_entries_validated] -is partially validated, and a general reference count is held. - -Unfortunately, in cases where an entry began with PTF_partial_set set, -and get_page_from_lNe() returns -EINVAL, the PTF_partial_set bit is -erroneously dropped. (This scenario can be engineered mainly by the -use of interleaving of promoting and demoting a page which has "linear -pagetable" entries; see the appendix for a sketch.) This means that -we will "leak" a general reference count on the page in question, -preventing the page from being freed. - -Fix this by setting page->partial_flags to the partial_flags local -variable. - -This is part of XSA-299. - -Reported-by: George Dunlap <george.dunlap@citrix.com> -Signed-off-by: George Dunlap <george.dunlap@citrix.com> -Reviewed-by: Jan Beulich <jbeulich@suse.com> ------ -Appendix - -Suppose A and B can both be promoted to L2 pages, and A[x] points to B. - -V1: PIN_L2 B. - B.type_count = 1 | PGT_validated - B.count = 2 | PGC_allocated - -V1: MOD_L3_ENTRY pointing something to A. - In the process of validating A[x], grab an extra type / ref on B: - B.type_count = 2 | PGT_validated - B.count = 3 | PGC_allocated - A.type_count = 1 | PGT_validated - A.count = 2 | PGC_allocated - -V1: UNPIN B. - B.type_count = 1 | PGT_validate - B.count = 2 | PGC_allocated - -V1: MOD_L3_ENTRY removing the reference to A. - De-validate A, down to A[x], which points to B. - Drop the final type on B. Arrange to be interrupted. - B.type_count = 1 | PGT_partial - B.count = 2 | PGC_allocated - A.type_count = 1 | PGT_partial - A.nr_validated_entries = x - A.partial_pte = -1 - -V2: MOD_L3_ENTRY adds a reference to A. - -At this point, get_page_from_l2e(A[x]) tries -get_page_and_type_from_mfn(), which fails because it's the wrong type; -and get_l2_linear_pagetable() also fails, because B isn't validated as -an l2 anymore. ---- - xen/arch/x86/mm.c | 6 +++--- - 1 file changed, 3 insertions(+), 3 deletions(-) - -diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c -index 886e93b8aa..0a094291da 100644 ---- a/xen/arch/x86/mm.c -+++ b/xen/arch/x86/mm.c -@@ -1581,7 +1581,7 @@ static int alloc_l2_table(struct page_info *page, unsigned long type) - if ( i ) - { - page->nr_validated_ptes = i; -- page->partial_flags = 0; -+ page->partial_flags = partial_flags; - current->arch.old_guest_ptpg = NULL; - current->arch.old_guest_table = page; - } -@@ -1674,7 +1674,7 @@ static int alloc_l3_table(struct page_info *page) - if ( i ) - { - page->nr_validated_ptes = i; -- page->partial_flags = 0; -+ page->partial_flags = partial_flags; - current->arch.old_guest_ptpg = NULL; - current->arch.old_guest_table = page; - } -@@ -1845,7 +1845,7 @@ static int alloc_l4_table(struct page_info *page) - if ( i ) - { - page->nr_validated_ptes = i; -- page->partial_flags = 0; -+ page->partial_flags = partial_flags; - if ( rc == -EINTR ) - rc = -ERESTART; - else --- -2.23.0 - |