From 0635cd9555ede02326afd274e8189ed3b70c1334 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= <berrange@redhat.com>
Date: Fri, 9 Aug 2024 11:28:24 +0100
Subject: [PATCH] util/xml: fix extraction of XML context
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Currently given an input of '<dom\n' we emit an error:

  error: Failed to define domain from tests/qemuxmlconfdata/broken-xml-invalid.xml
  error: at line 2: Couldn't find end of Start Tag dom line 1
  (null)
  ^

With this fix we emit:

  error: Failed to define domain from tests/qemuxmlconfdata/broken-xml-invalid.xml
  error: at line 2: Couldn't find end of Start Tag dom line 1
  <dom
  ----^

Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/util/virxml.c                                          | 5 +++++
 tests/qemuxmlconfdata/broken-xml-invalid.x86_64-latest.err | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/util/virxml.c b/src/util/virxml.c
index 51173303fe..38baeec5bb 100644
--- a/src/util/virxml.c
+++ b/src/util/virxml.c
@@ -1047,6 +1047,11 @@ catchXMLError(void *ctx, const char *msg G_GNUC_UNUSED, ...)
     cur = ctxt->input->cur;
     base = ctxt->input->base;
 
+    /* skip backwards over NUL terminator, in case we failed
+     * parsing at the EOF position */
+    if ((cur > base) && *cur == '\0')
+        cur--;
+
     /* skip backwards over any end-of-lines */
     while ((cur > base) && ((*(cur) == '\n') || (*(cur) == '\r')))
         cur--;
diff --git a/tests/qemuxmlconfdata/broken-xml-invalid.x86_64-latest.err b/tests/qemuxmlconfdata/broken-xml-invalid.x86_64-latest.err
index 35a1801371..a3bacd5d3a 100644
--- a/tests/qemuxmlconfdata/broken-xml-invalid.x86_64-latest.err
+++ b/tests/qemuxmlconfdata/broken-xml-invalid.x86_64-latest.err
@@ -1,3 +1,3 @@
 ABS_SRCDIR/qemuxmlconfdata/broken-xml-invalid.xml:2: Couldn't find end of Start Tag dom line 1
-(null)
-^
+<dom
+----^