[xen master] x86: replace bad ASSERT() in xenmem_add_to_physmap_one()

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[xen master] x86: replace bad ASSERT() in xenmem_add_to_physmap_one()

patchbot
commit f33d653f46f5889db7be4fef31d71bc871834c10
Author:     Jan Beulich <[hidden email]>
AuthorDate: Tue Nov 28 13:14:10 2017 +0100
Commit:     Jan Beulich <[hidden email]>
CommitDate: Tue Nov 28 13:14:10 2017 +0100

    x86: replace bad ASSERT() in xenmem_add_to_physmap_one()
   
    There are no locks being held, i.e. it is possible to be triggered by
    racy hypercall invocations. Subsequent code doesn't really depend on the
    checked values, so this is not a security issue.
   
    Signed-off-by: Jan Beulich <[hidden email]>
    Acked-by: Andrew Cooper <[hidden email]>
    Acked-by: George Dunlap <[hidden email]>
    Release-acked-by: Julien Grall <[hidden email]>
---
 xen/arch/x86/mm.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 886a5ee..86c822d 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4143,8 +4143,12 @@ int xenmem_add_to_physmap_one(
     /* Unmap from old location, if any. */
     old_gpfn = get_gpfn_from_mfn(mfn_x(mfn));
     ASSERT( old_gpfn != SHARED_M2P_ENTRY );
-    if ( space == XENMAPSPACE_gmfn || space == XENMAPSPACE_gmfn_range )
-        ASSERT( old_gpfn == gfn );
+    if ( (space == XENMAPSPACE_gmfn || space == XENMAPSPACE_gmfn_range) &&
+         old_gpfn != gfn )
+    {
+        rc = -EXDEV;
+        goto put_both;
+    }
     if ( old_gpfn != INVALID_M2P_ENTRY )
         rc = guest_physmap_remove_page(d, _gfn(old_gpfn), mfn, PAGE_ORDER_4K);
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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