44 lines
1.4 KiB
Diff
44 lines
1.4 KiB
Diff
References: CVE-2012-4537 XSA-22 bnc#786517
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x86/physmap: Prevent incorrect updates of m2p mappings
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In certain conditions, such as low memory, set_p2m_entry() can fail.
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Currently, the p2m and m2p tables will get out of sync because we still
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update the m2p table after the p2m update has failed.
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If that happens, subsequent guest-invoked memory operations can cause
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BUG()s and ASSERT()s to kill Xen.
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This is fixed by only updating the m2p table iff the p2m was
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successfully updated.
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This is a security problem, XSA-22 / CVE-2012-4537.
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Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Acked-by: Ian Campbell <ian.campbell@citrix.com>
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Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
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Index: xen-4.2.0-testing/xen/arch/x86/mm/p2m.c
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===================================================================
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--- xen-4.2.0-testing.orig/xen/arch/x86/mm/p2m.c
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+++ xen-4.2.0-testing/xen/arch/x86/mm/p2m.c
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@@ -654,7 +654,10 @@ guest_physmap_add_entry(struct domain *d
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if ( mfn_valid(_mfn(mfn)) )
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{
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if ( !set_p2m_entry(p2m, gfn, _mfn(mfn), page_order, t, p2m->default_access) )
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+ {
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rc = -EINVAL;
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+ goto out; /* Failed to update p2m, bail without updating m2p. */
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+ }
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if ( !p2m_is_grant(t) )
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{
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for ( i = 0; i < (1UL << page_order); i++ )
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@@ -677,6 +680,7 @@ guest_physmap_add_entry(struct domain *d
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}
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}
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+out:
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p2m_unlock(p2m);
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return rc;
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