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Diffstat (limited to 'system/xen/xsa/xsa247-4.9-0001-p2m-Always-check-to-see-if-removing-a-p2m-entry-actu.patch')
-rw-r--r--system/xen/xsa/xsa247-4.9-0001-p2m-Always-check-to-see-if-removing-a-p2m-entry-actu.patch176
1 files changed, 0 insertions, 176 deletions
diff --git a/system/xen/xsa/xsa247-4.9-0001-p2m-Always-check-to-see-if-removing-a-p2m-entry-actu.patch b/system/xen/xsa/xsa247-4.9-0001-p2m-Always-check-to-see-if-removing-a-p2m-entry-actu.patch
deleted file mode 100644
index ad9524a304..0000000000
--- a/system/xen/xsa/xsa247-4.9-0001-p2m-Always-check-to-see-if-removing-a-p2m-entry-actu.patch
+++ /dev/null
@@ -1,176 +0,0 @@
-From ad208b8b7e45fb2b7c572b86c61c26412609e82d Mon Sep 17 00:00:00 2001
-From: George Dunlap <george.dunlap@citrix.com>
-Date: Fri, 10 Nov 2017 16:53:54 +0000
-Subject: [PATCH 1/2] p2m: Always check to see if removing a p2m entry actually
- worked
-
-The PoD zero-check functions speculatively remove memory from the p2m,
-then check to see if it's completely zeroed, before putting it in the
-cache.
-
-Unfortunately, the p2m_set_entry() calls may fail if the underlying
-pagetable structure needs to change and the domain has exhausted its
-p2m memory pool: for instance, if we're removing a 2MiB region out of
-a 1GiB entry (in the p2m_pod_zero_check_superpage() case), or a 4k
-region out of a 2MiB or larger entry (in the p2m_pod_zero_check()
-case); and the return value is not checked.
-
-The underlying mfn will then be added into the PoD cache, and at some
-point mapped into another location in the p2m. If the guest
-afterwards ballons out this memory, it will be freed to the hypervisor
-and potentially reused by another domain, in spite of the fact that
-the original domain still has writable mappings to it.
-
-There are several places where p2m_set_entry() shouldn't be able to
-fail, as it is guaranteed to write an entry of the same order that
-succeeded before. Add a backstop of crashing the domain just in case,
-and an ASSERT_UNREACHABLE() to flag up the broken assumption on debug
-builds.
-
-While we're here, use PAGE_ORDER_2M rather than a magic constant.
-
-This is part of XSA-247.
-
-Reported-by: George Dunlap <george.dunlap.com>
-Signed-off-by: George Dunlap <george.dunlap@citrix.com>
-Reviewed-by: Jan Beulich <jbeulich@suse.com>
----
-v4:
-- Removed some training whitespace
-v3:
-- Reformat reset clause to be more compact
-- Make sure to set map[i] = NULL when unmapping in case we need to bail
-v2:
-- Crash a domain if a p2m_set_entry we think cannot fail fails anyway.
----
- xen/arch/x86/mm/p2m-pod.c | 77 +++++++++++++++++++++++++++++++++++++----------
- 1 file changed, 61 insertions(+), 16 deletions(-)
-
-diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c
-index 730a48f928..f2ed751892 100644
---- a/xen/arch/x86/mm/p2m-pod.c
-+++ b/xen/arch/x86/mm/p2m-pod.c
-@@ -752,8 +752,10 @@ p2m_pod_zero_check_superpage(struct p2m_domain *p2m, unsigned long gfn)
- }
-
- /* Try to remove the page, restoring old mapping if it fails. */
-- p2m_set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_2M,
-- p2m_populate_on_demand, p2m->default_access);
-+ if ( p2m_set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_2M,
-+ p2m_populate_on_demand, p2m->default_access) )
-+ goto out;
-+
- p2m_tlb_flush_sync(p2m);
-
- /* Make none of the MFNs are used elsewhere... for example, mapped
-@@ -810,9 +812,18 @@ p2m_pod_zero_check_superpage(struct p2m_domain *p2m, unsigned long gfn)
- ret = SUPERPAGE_PAGES;
-
- out_reset:
-- if ( reset )
-- p2m_set_entry(p2m, gfn, mfn0, 9, type0, p2m->default_access);
--
-+ /*
-+ * This p2m_set_entry() call shouldn't be able to fail, since the same order
-+ * on the same gfn succeeded above. If that turns out to be false, crashing
-+ * the domain should be the safest way of making sure we don't leak memory.
-+ */
-+ if ( reset && p2m_set_entry(p2m, gfn, mfn0, PAGE_ORDER_2M,
-+ type0, p2m->default_access) )
-+ {
-+ ASSERT_UNREACHABLE();
-+ domain_crash(d);
-+ }
-+
- out:
- gfn_unlock(p2m, gfn, SUPERPAGE_ORDER);
- return ret;
-@@ -869,19 +880,30 @@ p2m_pod_zero_check(struct p2m_domain *p2m, unsigned long *gfns, int count)
- }
-
- /* Try to remove the page, restoring old mapping if it fails. */
-- p2m_set_entry(p2m, gfns[i], INVALID_MFN, PAGE_ORDER_4K,
-- p2m_populate_on_demand, p2m->default_access);
-+ if ( p2m_set_entry(p2m, gfns[i], INVALID_MFN, PAGE_ORDER_4K,
-+ p2m_populate_on_demand, p2m->default_access) )
-+ goto skip;
-
- /* See if the page was successfully unmapped. (Allow one refcount
- * for being allocated to a domain.) */
- if ( (mfn_to_page(mfns[i])->count_info & PGC_count_mask) > 1 )
- {
-+ /*
-+ * If the previous p2m_set_entry call succeeded, this one shouldn't
-+ * be able to fail. If it does, crashing the domain should be safe.
-+ */
-+ if ( p2m_set_entry(p2m, gfns[i], mfns[i], PAGE_ORDER_4K,
-+ types[i], p2m->default_access) )
-+ {
-+ ASSERT_UNREACHABLE();
-+ domain_crash(d);
-+ goto out_unmap;
-+ }
-+
-+ skip:
- unmap_domain_page(map[i]);
- map[i] = NULL;
-
-- p2m_set_entry(p2m, gfns[i], mfns[i], PAGE_ORDER_4K,
-- types[i], p2m->default_access);
--
- continue;
- }
- }
-@@ -900,12 +922,25 @@ p2m_pod_zero_check(struct p2m_domain *p2m, unsigned long *gfns, int count)
-
- unmap_domain_page(map[i]);
-
-- /* See comment in p2m_pod_zero_check_superpage() re gnttab
-- * check timing. */
-- if ( j < PAGE_SIZE/sizeof(*map[i]) )
-+ map[i] = NULL;
-+
-+ /*
-+ * See comment in p2m_pod_zero_check_superpage() re gnttab
-+ * check timing.
-+ */
-+ if ( j < (PAGE_SIZE / sizeof(*map[i])) )
- {
-- p2m_set_entry(p2m, gfns[i], mfns[i], PAGE_ORDER_4K,
-- types[i], p2m->default_access);
-+ /*
-+ * If the previous p2m_set_entry call succeeded, this one shouldn't
-+ * be able to fail. If it does, crashing the domain should be safe.
-+ */
-+ if ( p2m_set_entry(p2m, gfns[i], mfns[i], PAGE_ORDER_4K,
-+ types[i], p2m->default_access) )
-+ {
-+ ASSERT_UNREACHABLE();
-+ domain_crash(d);
-+ goto out_unmap;
-+ }
- }
- else
- {
-@@ -929,7 +964,17 @@ p2m_pod_zero_check(struct p2m_domain *p2m, unsigned long *gfns, int count)
- p2m->pod.entry_count++;
- }
- }
--
-+
-+ return;
-+
-+out_unmap:
-+ /*
-+ * Something went wrong, probably crashing the domain. Unmap
-+ * everything and return.
-+ */
-+ for ( i = 0; i < count; i++ )
-+ if ( map[i] )
-+ unmap_domain_page(map[i]);
- }
-
- #define POD_SWEEP_LIMIT 1024
---
-2.15.0
-
generated by cgit v1.2.3 (git 2.26.2) at 2024-12-13 16:17:12 +0000