[PATCH 1/2] xen/rangeset: fix incorrect subtraction

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Given the following rangset operation:

{ [0, 1], [4, 5] } - { [3, 4] }

The current rangeset logic will output a rangeset:

{ [0, 2], [5, 5] }

This is incorrect, and also has the undesirable property of being bogus in
a way that the resulting rangeset is expanded.

Fix this by making sure the bounds are correctly checked before modifying
the previous range.

Fixes: 484a058c4828 ('Add auto-destructing per-domain rangeset data 
structure...')
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/common/rangeset.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/common/rangeset.c b/xen/common/rangeset.c
index b75590f90744..e75871039087 100644
--- a/xen/common/rangeset.c
+++ b/xen/common/rangeset.c
@@ -227,7 +227,8 @@ int rangeset_remove_range(
 
         if ( x->s < s )
         {
-            x->e = s - 1;
+            if ( x->e >= s )
+                x->e = s - 1;
             x = next_range(r, x);
         }
 
-- 
2.48.1