[vhostmd PATCH 01/18] libmetrics: Set pointer NULL after free

[Jim Fehlig <jfehlig@xxxxxxxx>]

>From a coverity scan

vhostmd-1.1/libmetrics/libmetrics.c:185:10: warning: Attempt to free released memory
         free(mdisk->buffer);

Some error conditions will call mdisk_content_free(), which could result
in a double-free when the entire mdisk is freed and mdisk_content_free()
is called again. Protect agains these potential double-frees by setting
the mdisk contents NULL after freeing them.

Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
---
 libmetrics/libmetrics.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/libmetrics/libmetrics.c b/libmetrics/libmetrics.c
index 6c80681..a5582e7 100644
--- a/libmetrics/libmetrics.c
+++ b/libmetrics/libmetrics.c
@@ -177,14 +177,22 @@ static metric_disk * mdisk_alloc()
 static void mdisk_content_free()
 {
    if (mdisk) {
-      if (mdisk->doc)
-          xmlFreeDoc(mdisk->doc);
-      if (mdisk->pctxt)
-         xmlFreeParserCtxt(mdisk->pctxt);
-      if (mdisk->buffer)
-         free(mdisk->buffer);
-      if (mdisk->disk_name)
-         free(mdisk->disk_name);
+       if (mdisk->doc) {
+           xmlFreeDoc(mdisk->doc);
+           mdisk->doc = NULL;
+       }
+       if (mdisk->pctxt) {
+           xmlFreeParserCtxt(mdisk->pctxt);
+           mdisk->pctxt = NULL;
+       }
+       if (mdisk->buffer) {
+           free(mdisk->buffer);
+           mdisk->buffer = NULL;
+       }
+       if (mdisk->disk_name) {
+           free(mdisk->disk_name);
+           mdisk->disk_name = NULL;
+       }
    }
 }
 
-- 
2.16.4


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