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| author | Ian Jackson <Ian.Jackson@eu.citrix.com> | 2012-11-14 11:44:46 +0000 |
|---|---|---|
| committer | Ian Jackson <Ian.Jackson@eu.citrix.com> | 2012-11-14 11:44:46 +0000 |
| commit | e201bce9a19d158ee979ed9a6690cfeede925c1f (patch) | |
| tree | d8900da3c75b69ca51b8edc344bef00f06611315 | |
| parent | e7dc3458699a97d8bdac6be9bde94751ef12bb3f (diff) | |
| download | xen-e201bce9a19d158ee979ed9a6690cfeede925c1f.tar.gz xen-e201bce9a19d158ee979ed9a6690cfeede925c1f.tar.bz2 xen-e201bce9a19d158ee979ed9a6690cfeede925c1f.zip | |
xen/mm/shadow: check toplevel pagetables are present before unhooking them.
If the guest has not fully populated its top-level PAE entries when it calls
HVMOP_pagetable_dying, the shadow code could try to unhook entries from
MFN 0. Add a check to avoid that case.
This issue was introduced by c/s 21239:b9d2db109cf5.
This is a security problem, XSA-23 / CVE-2012-4538.
Signed-off-by: Tim Deegan <tim@xen.org>
Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
xen-4.1-testing changeset: 23409:61eb3d030f52
Backport-requested-by: security@xen.org
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
| -rw-r--r-- | xen/arch/x86/mm/shadow/multi.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c index ca7635b416..243b9f4d44 100644 --- a/xen/arch/x86/mm/shadow/multi.c +++ b/xen/arch/x86/mm/shadow/multi.c @@ -4698,8 +4698,12 @@ static void sh_pagetable_dying(struct vcpu *v, paddr_t gpa) } for ( i = 0; i < 4; i++ ) { - if ( fast_path ) - smfn = _mfn(pagetable_get_pfn(v->arch.shadow_table[i])); + if ( fast_path ) { + if ( pagetable_is_null(v->arch.shadow_table[i]) ) + smfn = _mfn(INVALID_MFN); + else + smfn = _mfn(pagetable_get_pfn(v->arch.shadow_table[i])); + } else { /* retrieving the l2s */ |