55 lines
2.1 KiB
Diff
55 lines
2.1 KiB
Diff
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References: bnc#840593 CVE-2013-4356 XSA-64
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x86/mm/shadow: Fix initialization of PV shadow L4 tables.
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Shadowed PV L4 tables must have the same Xen mappings as their
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unshadowed equivalent. This is done by copying the Xen entries
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verbatim from the idle pagetable, and then using guest_l4_slot()
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in the SHADOW_FOREACH_L4E() iterator to avoid touching those entries.
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adc5afbf1c70ef55c260fb93e4b8ce5ccb918706 (x86: support up to 16Tb)
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changed the definition of ROOT_PAGETABLE_XEN_SLOTS to extend right to
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the top of the address space, which causes the shadow code to
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copy Xen mappings into guest-kernel-address slots too.
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In the common case, all those slots are zero in the idle pagetable,
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and no harm is done. But if any slot above #271 is non-zero, Xen will
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crash when that slot is later cleared (it attempts to drop
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shadow-pagetable refcounts on its own L4 pagetables).
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Fix by using the new ROOT_PAGETABLE_PV_XEN_SLOTS when appropriate.
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Monitor pagetables need the full Xen mappings, so they keep using the
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old name (with its new semantics).
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This is CVE-2013-4356 / XSA-64.
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Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Signed-off-by: Tim Deegan <tim@xen.org>
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Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Reviewed-by: Jan Beulich <jbeulich@suse.com>
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--- a/xen/arch/x86/mm/shadow/multi.c
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+++ b/xen/arch/x86/mm/shadow/multi.c
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@@ -1433,15 +1433,19 @@ void sh_install_xen_entries_in_l4(struct
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{
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struct domain *d = v->domain;
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shadow_l4e_t *sl4e;
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+ unsigned int slots;
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sl4e = sh_map_domain_page(sl4mfn);
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ASSERT(sl4e != NULL);
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ASSERT(sizeof (l4_pgentry_t) == sizeof (shadow_l4e_t));
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-
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+
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/* Copy the common Xen mappings from the idle domain */
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+ slots = (shadow_mode_external(d)
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+ ? ROOT_PAGETABLE_XEN_SLOTS
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+ : ROOT_PAGETABLE_PV_XEN_SLOTS);
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memcpy(&sl4e[ROOT_PAGETABLE_FIRST_XEN_SLOT],
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&idle_pg_table[ROOT_PAGETABLE_FIRST_XEN_SLOT],
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- ROOT_PAGETABLE_XEN_SLOTS * sizeof(l4_pgentry_t));
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+ slots * sizeof(l4_pgentry_t));
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/* Install the per-domain mappings for this domain */
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sl4e[shadow_l4_table_offset(PERDOMAIN_VIRT_START)] =
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