36 lines
1.3 KiB
Diff
36 lines
1.3 KiB
Diff
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References: CVE-2012-4538 XSA-23 bnc#786519
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xen/mm/shadow: check toplevel pagetables are present before unhooking them.
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If the guest has not fully populated its top-level PAE entries when it calls
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HVMOP_pagetable_dying, the shadow code could try to unhook entries from
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MFN 0. Add a check to avoid that case.
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This issue was introduced by c/s 21239:b9d2db109cf5.
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This is a security problem, XSA-23 / CVE-2012-4538.
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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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Acked-by: Ian Campbell <ian.campbell@citrix.com>
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Index: xen-4.2.0-testing/xen/arch/x86/mm/shadow/multi.c
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===================================================================
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--- xen-4.2.0-testing.orig/xen/arch/x86/mm/shadow/multi.c
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+++ xen-4.2.0-testing/xen/arch/x86/mm/shadow/multi.c
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@@ -4734,8 +4734,12 @@ static void sh_pagetable_dying(struct vc
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unsigned long gfn;
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mfn_t smfn, gmfn;
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- if ( fast_path )
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- smfn = _mfn(pagetable_get_pfn(v->arch.shadow_table[i]));
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+ if ( fast_path ) {
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+ if ( pagetable_is_null(v->arch.shadow_table[i]) )
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+ smfn = _mfn(INVALID_MFN);
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+ else
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+ smfn = _mfn(pagetable_get_pfn(v->arch.shadow_table[i]));
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+ }
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else
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{
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/* retrieving the l2s */
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