[Xen-devel] [PATCH v3 3/5] xenstore: add explicit memory context parameter to read_node()

[Juergen Gross <jgross@xxxxxxxx>]

Add a parameter to xenstored read_node() function to explicitly
specify the memory context to be used for allocations. This will make
it easier to avoid memory leaks by using a context which is freed
soon.

When calling read_node() select a sensible memory context for the new
parameter by preferring a temporary one.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/xenstore/xenstored_core.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index f2c12ab..c462115 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -397,8 +397,12 @@ bool is_child(const char *child, const char *parent)
        return child[len] == '/' || child[len] == '\0';
 }
 
-/* If it fails, returns NULL and sets errno. */
-static struct node *read_node(struct connection *conn, const char *name)
+/*
+ * If it fails, returns NULL and sets errno.
+ * Temporary memory allocations will be done with ctx.
+ */
+static struct node *read_node(struct connection *conn, const void *ctx,
+                             const char *name)
 {
        TDB_DATA key, data;
        uint32_t *p;
@@ -419,7 +423,7 @@ static struct node *read_node(struct connection *conn, 
const char *name)
                return NULL;
        }
 
-       node = talloc(name, struct node);
+       node = talloc(ctx, struct node);
        node->name = talloc_strdup(node, name);
        node->parent = NULL;
        node->tdb = tdb_context(conn);
@@ -526,7 +530,7 @@ static enum xs_perm_type ask_parents(struct connection 
*conn, const char *name)
 
        do {
                name = get_parent(name, name);
-               node = read_node(conn, name);
+               node = read_node(conn, name, name);
                if (node)
                        break;
        } while (!streq(name, "/"));
@@ -567,7 +571,7 @@ struct node *get_node(struct connection *conn,
                errno = EINVAL;
                return NULL;
        }
-       node = read_node(conn, name);
+       node = read_node(conn, name, name);
        /* If we don't have permission, we don't have node. */
        if (node) {
                if ((perm_for_conn(conn, node->perms, node->num_perms) & perm)
@@ -823,7 +827,7 @@ static struct node *construct_node(struct connection *conn, 
const char *name)
        char *children, *parentname = get_parent(name, name);
 
        /* If parent doesn't exist, create it. */
-       parent = read_node(conn, parentname);
+       parent = read_node(conn, parentname, parentname);
        if (!parent)
                parent = construct_node(conn, parentname);
        if (!parent)
@@ -988,7 +992,7 @@ static void delete_node(struct connection *conn, struct 
node *node)
        for (i = 0; i < node->childlen; i += strlen(node->children+i) + 1) {
                struct node *child;
 
-               child = read_node(conn, 
+               child = read_node(conn, node,
                                  talloc_asprintf(node, "%s/%s", node->name,
                                                  node->children + i));
                if (child) {
@@ -1040,7 +1044,7 @@ static int _rm(struct connection *conn, struct node 
*node, const char *name)
        /* Delete from parent first, then if we crash, the worst that can
           happen is the child will continue to take up space, but will
           otherwise be unreachable. */
-       struct node *parent = read_node(conn, get_parent(name, name));
+       struct node *parent = read_node(conn, name, get_parent(name, name));
        if (!parent) {
                send_error(conn, EINVAL);
                return 0;
@@ -1059,7 +1063,7 @@ static int _rm(struct connection *conn, struct node 
*node, const char *name)
 static void internal_rm(const char *name)
 {
        char *tname = talloc_strdup(NULL, name);
-       struct node *node = read_node(NULL, tname);
+       struct node *node = read_node(NULL, tname, tname);
        if (node)
                _rm(NULL, node, tname);
        talloc_free(node);
@@ -1077,7 +1081,7 @@ static void do_rm(struct connection *conn, struct 
buffered_data *in)
        if (!node) {
                /* Didn't exist already?  Fine, if parent exists. */
                if (errno == ENOENT) {
-                       node = read_node(conn, get_parent(in, name));
+                       node = read_node(conn, in, get_parent(in, name));
                        if (node) {
                                send_ack(conn, XS_RM);
                                return;
@@ -1608,7 +1612,7 @@ static void remember_string(struct hashtable *hash, const 
char *str)
  */
 static void check_store_(const char *name, struct hashtable *reachable)
 {
-       struct node *node = read_node(NULL, name);
+       struct node *node = read_node(NULL, name, name);
 
        if (node) {
                size_t i = 0;
@@ -1622,7 +1626,8 @@ static void check_store_(const char *name, struct 
hashtable *reachable)
                        size_t childlen = strlen(node->children + i);
                        char * childname = child_name(node->name,
                                                      node->children + i);
-                       struct node *childnode = read_node(NULL, childname);
+                       struct node *childnode = read_node(NULL, childname,
+                                                          childname);
                        
                        if (childnode) {
                                if (hashtable_search(children, childname)) {
-- 
2.6.6


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