From: Roger Pau Monné <roger.pau@citrix.com>
Date: Tue, 29 Apr 2025 09:43:12 +0000 (+0200)
Subject: xen/rangeset: fix incorrect subtraction
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=6b399ed19fd36cca92745a55901a89c3b5fb747f;p=xen.git

xen/rangeset: fix incorrect subtraction

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@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: e118fc98e7ae652a188d227bd7ea22f132724150
master date: 2025-04-11 12:20:10 +0200
---

diff --git a/xen/common/rangeset.c b/xen/common/rangeset.c
index b75590f907..e758710390 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);
         }