[PATCH v2] qemu_namespace: Don't leak mknod items that are being skipped over

[Michal Privoznik]

When building and populating domain NS a couple of functions are
called that append paths to a string list. This string list is
then inspected, one item at the time by
qemuNamespacePrepareOneItem() which gathers all the info for
given path (stat buffer, possible link target, ACLs, SELinux
label) using qemuNamespaceMknodItemInit(). If the path needs to
be created in the domain's private /dev then it's added onto this
qemuNamespaceMknodData list which is freed later in the process.
But, if the path does not need to be created in the domain's
private /dev, then the memory allocated by
qemuNamespaceMknodItemInit() is not freed anywhere leading to a
leak.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---

v2 of:

https://www.redhat.com/archives/libvir-list/2020-September/msg00248.html

diff to v2:
- autocleanup approach is implemented in qemuNamespacePrepareOneItem()

 src/qemu/qemu_namespace.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/qemu/qemu_namespace.c b/src/qemu/qemu_namespace.c
index 87f4fd8d58..b0d1d0d083 100644
--- a/src/qemu/qemu_namespace.c
+++ b/src/qemu/qemu_namespace.c
@@ -871,7 +871,7 @@ qemuDomainNamespaceAvailable(qemuDomainNamespace ns G_GNUC_UNUSED)
 typedef struct _qemuNamespaceMknodItem qemuNamespaceMknodItem;
 typedef qemuNamespaceMknodItem *qemuNamespaceMknodItemPtr;
 struct _qemuNamespaceMknodItem {
-    const char *file;
+    char *file;
     char *target;
     bool bindmounted;
     GStatBuf sb;
@@ -892,6 +892,7 @@ struct _qemuNamespaceMknodData {
 static void
 qemuNamespaceMknodItemClear(qemuNamespaceMknodItemPtr item)
 {
+    VIR_FREE(item->file);
     VIR_FREE(item->target);
     virFileFreeACLs(&item->acl);
 #ifdef WITH_SELINUX
@@ -900,6 +901,8 @@ qemuNamespaceMknodItemClear(qemuNamespaceMknodItemPtr item)
 }
 
 
+G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(qemuNamespaceMknodItem, qemuNamespaceMknodItemClear);
+
 static void
 qemuNamespaceMknodDataClear(qemuNamespaceMknodDataPtr data)
 {
@@ -1091,7 +1094,7 @@ qemuNamespaceMknodItemInit(qemuNamespaceMknodItemPtr item,
     bool isLink;
     bool needsBindMount;
 
-    item->file = file;
+    item->file = g_strdup(file);
 
     if (g_lstat(file, &item->sb) < 0) {
         if (errno == ENOENT)
@@ -1166,11 +1169,13 @@ qemuNamespacePrepareOneItem(qemuNamespaceMknodDataPtr data,
                             size_t ndevMountsPath)
 {
     long ttl = sysconf(_SC_SYMLOOP_MAX);
-    const char *next = file;
+    g_autofree char *next = g_strdup(file);
     size_t i;
 
     while (1) {
-        qemuNamespaceMknodItem item = { 0 };
+        g_auto(qemuNamespaceMknodItem) item = { 0 };
+        bool isLink;
+        bool addToData = false;
         int rc;
 
         rc = qemuNamespaceMknodItemInit(&item, cfg, vm, next);
@@ -1182,6 +1187,8 @@ qemuNamespacePrepareOneItem(qemuNamespaceMknodDataPtr data,
             return -1;
         }
 
+        isLink = S_ISLNK(item.sb.st_mode);
+
         if (STRPREFIX(next, QEMU_DEVPREFIX)) {
             for (i = 0; i < ndevMountsPath; i++) {
                 if (STREQ(devMountsPath[i], "/dev"))
@@ -1190,12 +1197,18 @@ qemuNamespacePrepareOneItem(qemuNamespaceMknodDataPtr data,
                     break;
             }
 
-            if (i == ndevMountsPath &&
-                VIR_APPEND_ELEMENT_COPY(data->items, data->nitems, item) < 0)
-                return -1;
+            if (i == ndevMountsPath)
+                addToData = true;
         }
 
-        if (!S_ISLNK(item.sb.st_mode))
+        g_free(next);
+        next = g_strdup(item.target);
+
+        if (addToData &&
+            VIR_APPEND_ELEMENT(data->items, data->nitems, item) < 0)
+            return -1;
+
+        if (!isLink)
             break;
 
         if (ttl-- == 0) {
@@ -1204,8 +1217,6 @@ qemuNamespacePrepareOneItem(qemuNamespaceMknodDataPtr data,
                                  next);
             return -1;
         }
-
-        next = item.target;
     }
 
     return 0;
-- 
2.26.2