[xen stable-4.13] libxc/restore: Fix REC_TYPE_X86_PV_VCPU_XSAVE data auditing (take 2)

[patchbot@xxxxxxx]

commit d2aecd86c4481291b260869c47cf0a9a02321564
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Feb 4 20:29:38 2020 +0000
Commit:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CommitDate: Tue May 5 15:49:10 2020 +0100

    libxc/restore: Fix REC_TYPE_X86_PV_VCPU_XSAVE data auditing (take 2)
    
    It turns out that a bug (since forever) in Xen causes XSAVE records to have
    non-architectural behaviour on xsave-capable hardware, when a PV guest has 
not
    touched the state.
    
    In such a case, the data record returned from Xen is 2*uint64_t, both 
claiming
    the (illegitimate) state of %xcr0 and %xcr0_accum being 0.
    
    Adjust the bound in handle_x86_pv_vcpu_blob() to cope with this.
    
    Fixes: 2a62c22715b "libxc/restore: Fix data auditing in 
handle_x86_pv_vcpu_blob()"
    Reported-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Wei Liu <wl@xxxxxxx>
    (cherry picked from commit 0729830cc425a8ff27a3137e87b93768ae3c853c)
---
 tools/libxc/xc_sr_restore_x86_pv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/libxc/xc_sr_restore_x86_pv.c 
b/tools/libxc/xc_sr_restore_x86_pv.c
index c673b2670c..ee8b62ce58 100644
--- a/tools/libxc/xc_sr_restore_x86_pv.c
+++ b/tools/libxc/xc_sr_restore_x86_pv.c
@@ -825,10 +825,10 @@ static int handle_x86_pv_vcpu_blob(struct xc_sr_context 
*ctx,
         break;
 
     case REC_TYPE_X86_PV_VCPU_XSAVE:
-        if ( blobsz < 128 )
+        if ( blobsz < 16 )
         {
             ERROR("%s record too short: min %zu, got %u",
-                  rec_name, sizeof(*vhdr) + 128, rec->length);
+                  rec_name, sizeof(*vhdr) + 16, rec->length);
             goto out;
         }
         break;
--
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