49 lines
1.9 KiB
Diff
49 lines
1.9 KiB
Diff
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x86/shadow: fix race condition sampling the dirty vram state
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d->arch.hvm_domain.dirty_vram must be read with the domain's paging lock held.
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If not, two concurrent hypercalls could both end up attempting to free
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dirty_vram (the second of which will free a wild pointer), or both end up
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allocating a new dirty_vram structure (the first of which will be leaked).
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This is XSA-104.
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Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Reviewed-by: Tim Deegan <tim@xen.org>
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Index: xen-4.4.1-testing/xen/arch/x86/mm/shadow/common.c
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===================================================================
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--- xen-4.4.1-testing.orig/xen/arch/x86/mm/shadow/common.c
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+++ xen-4.4.1-testing/xen/arch/x86/mm/shadow/common.c
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@@ -3486,7 +3486,7 @@ int shadow_track_dirty_vram(struct domai
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int flush_tlb = 0;
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unsigned long i;
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p2m_type_t t;
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- struct sh_dirty_vram *dirty_vram = d->arch.hvm_domain.dirty_vram;
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+ struct sh_dirty_vram *dirty_vram;
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struct p2m_domain *p2m = p2m_get_hostp2m(d);
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if ( end_pfn < begin_pfn || end_pfn > p2m->max_mapped_pfn + 1 )
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@@ -3496,6 +3496,8 @@ int shadow_track_dirty_vram(struct domai
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p2m_lock(p2m_get_hostp2m(d));
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paging_lock(d);
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+ dirty_vram = d->arch.hvm_domain.dirty_vram;
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+
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if ( dirty_vram && (!nr ||
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( begin_pfn != dirty_vram->begin_pfn
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|| end_pfn != dirty_vram->end_pfn )) )
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Index: xen-4.4.1-testing/xen/include/asm-x86/hvm/domain.h
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===================================================================
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--- xen-4.4.1-testing.orig/xen/include/asm-x86/hvm/domain.h
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+++ xen-4.4.1-testing/xen/include/asm-x86/hvm/domain.h
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@@ -67,7 +67,7 @@ struct hvm_domain {
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/* Memory ranges with pinned cache attributes. */
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struct list_head pinned_cacheattr_ranges;
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- /* VRAM dirty support. */
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+ /* VRAM dirty support. Protect with the domain paging lock. */
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struct sh_dirty_vram *dirty_vram;
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/* If one of vcpus of this domain is in no_fill_mode or
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