File xs-04-get_node-context.patch of Package xen.4506
commit ab32687503e054a72ebcede9b7aa34ef856634f6
Author: Juergen Gross <jgross@suse.com>
Date: Tue Jul 19 13:30:45 2016 +0200
xenstore: add explicit memory context parameter to get_node()
Add a parameter to xenstored get_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.
This requires adding the temporary context to errno_from_parents() and
ask_parents(), too.
When calling get_node() select a sensible memory context for the new
parameter by preferring a temporary one.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index b7244bb..7575dd9 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -533,14 +533,18 @@ static char *get_parent(const void *ctx, const char *node)
return talloc_asprintf(ctx, "%.*s", (int)(slash - node), node);
}
-/* What do parents say? */
-static enum xs_perm_type ask_parents(struct connection *conn, const char *name)
+/*
+ * What do parents say?
+ * Temporary memory allocations are done with ctx.
+ */
+static enum xs_perm_type ask_parents(struct connection *conn, const void *ctx,
+ const char *name)
{
struct node *node;
do {
- name = get_parent(name, name);
- node = read_node(conn, name, name);
+ name = get_parent(ctx, name);
+ node = read_node(conn, ctx, name);
if (node)
break;
} while (!streq(name, "/"));
@@ -554,24 +558,32 @@ static enum xs_perm_type ask_parents(struct connection *conn, const char *name)
return perm_for_conn(conn, node->perms, node->num_perms);
}
-/* We have a weird permissions system. You can allow someone into a
+/*
+ * We have a weird permissions system. You can allow someone into a
* specific node without allowing it in the parents. If it's going to
* fail, however, we don't want the errno to indicate any information
- * about the node. */
-static int errno_from_parents(struct connection *conn, const char *node,
- int errnum, enum xs_perm_type perm)
+ * about the node.
+ * Temporary memory allocations are done with ctx.
+ */
+static int errno_from_parents(struct connection *conn, const void *ctx,
+ const char *node, int errnum,
+ enum xs_perm_type perm)
{
/* We always tell them about memory failures. */
if (errnum == ENOMEM)
return errnum;
- if (ask_parents(conn, node) & perm)
+ if (ask_parents(conn, ctx, node) & perm)
return errnum;
return EACCES;
}
-/* If it fails, returns NULL and sets errno. */
+/*
+ * If it fails, returns NULL and sets errno.
+ * Temporary memory allocations are done with ctx.
+ */
struct node *get_node(struct connection *conn,
+ const void *ctx,
const char *name,
enum xs_perm_type perm)
{
@@ -581,7 +593,7 @@ struct node *get_node(struct connection *conn,
errno = EINVAL;
return NULL;
}
- node = read_node(conn, name, name);
+ node = read_node(conn, ctx, 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)
@@ -592,7 +604,7 @@ struct node *get_node(struct connection *conn,
}
/* Clean up errno if they weren't supposed to know. */
if (!node)
- errno = errno_from_parents(conn, name, errno, perm);
+ errno = errno_from_parents(conn, ctx, name, errno, perm);
return node;
}
@@ -785,7 +797,7 @@ static void send_directory(struct connection *conn, struct buffered_data *in)
const char *name = onearg(in);
name = canonicalize(conn, name);
- node = get_node(conn, name, XS_PERM_READ);
+ node = get_node(conn, in, name, XS_PERM_READ);
if (!node) {
send_error(conn, errno);
return;
@@ -800,7 +812,7 @@ static void do_read(struct connection *conn, struct buffered_data *in)
const char *name = onearg(in);
name = canonicalize(conn, name);
- node = get_node(conn, name, XS_PERM_READ);
+ node = get_node(conn, in, name, XS_PERM_READ);
if (!node) {
send_error(conn, errno);
return;
@@ -937,7 +949,7 @@ static void do_write(struct connection *conn, struct buffered_data *in)
datalen = in->used - offset;
name = canonicalize(conn, vec[0]);
- node = get_node(conn, name, XS_PERM_WRITE);
+ node = get_node(conn, in, name, XS_PERM_WRITE);
if (!node) {
/* No permissions, invalid input? */
if (errno != ENOENT) {
@@ -969,7 +981,7 @@ static void do_mkdir(struct connection *conn, struct buffered_data *in)
const char *name = onearg(in);
name = canonicalize(conn, name);
- node = get_node(conn, name, XS_PERM_WRITE);
+ node = get_node(conn, in, name, XS_PERM_WRITE);
/* If it already exists, fine. */
if (!node) {
@@ -1087,7 +1099,7 @@ static void do_rm(struct connection *conn, struct buffered_data *in)
const char *name = onearg(in);
name = canonicalize(conn, name);
- node = get_node(conn, name, XS_PERM_WRITE);
+ node = get_node(conn, in, name, XS_PERM_WRITE);
if (!node) {
/* Didn't exist already? Fine, if parent exists. */
if (errno == ENOENT) {
@@ -1124,7 +1136,7 @@ static void do_get_perms(struct connection *conn, struct buffered_data *in)
unsigned int len;
name = canonicalize(conn, name);
- node = get_node(conn, name, XS_PERM_READ);
+ node = get_node(conn, in, name, XS_PERM_READ);
if (!node) {
send_error(conn, errno);
return;
@@ -1156,7 +1168,7 @@ static void do_set_perms(struct connection *conn, struct buffered_data *in)
num--;
/* We must own node to do this (tools can do this too). */
- node = get_node(conn, name, XS_PERM_WRITE|XS_PERM_OWNER);
+ node = get_node(conn, in, name, XS_PERM_WRITE|XS_PERM_OWNER);
if (!node) {
send_error(conn, errno);
return;
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index 5dbf9c8..ecc614f 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -149,6 +149,7 @@ bool check_event_node(const char *node);
/* Get this node, checking we have permissions. */
struct node *get_node(struct connection *conn,
+ const void *ctx,
const char *name,
enum xs_perm_type perm);
diff --git a/tools/xenstore/xenstored_watch.c b/tools/xenstore/xenstored_watch.c
index 8543999..beefd6c 100644
--- a/tools/xenstore/xenstored_watch.c
+++ b/tools/xenstore/xenstored_watch.c
@@ -57,7 +57,7 @@ static void add_event(struct connection *conn,
if (!check_event_node(name)) {
/* Can this conn load node, or see that it doesn't exist? */
- struct node *node = get_node(conn, name, XS_PERM_READ);
+ struct node *node = get_node(conn, name, name, XS_PERM_READ);
/*
* XXX We allow EACCES here because otherwise a non-dom0
* backend driver cannot watch for disappearance of a frontend
