xenstore size limits

 * Documents the existing 4kby size limit on xenstore message payloads
 * Causes xs.c in libxenstore to fail locally rather than violating
   said limit (which is good because xenstored kills the client
   connection if it's exceeded).
 * Introduces some limits on path lengths in xenstored.  I trust
   no-one is using path lengths >2kby.  This is good because currently
   a domain client can create a 4kby relative path that the dom0 tools
   cannot access since they'd have to specify the somewhat longer
   absolute path.
 * Removes uses of the host's PATH_MAX (!)

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

4 files changed, 14 insertions, 2 deletions

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 825d834e37..acf6dd3918 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -672,6 +672,9 @@ bool is_valid_nodename(const char *node)
 	if (strstr(node, "//"))
 		return false;
 
+	if (strlen(node) > XENSTORE_ABS_PATH_MAX)
+		return false;
+
 	return valid_chars(node);
 }
 
@@ -1281,7 +1284,7 @@ static void handle_input(struct connection *conn)
 		if (in->used != sizeof(in->hdr))
 			return;
 
-		if (in->hdr.msg.len > PATH_MAX) {
+		if (in->hdr.msg.len > XENSTORE_PAYLOAD_MAX) {
 			syslog(LOG_ERR, "Client tried to feed us %i",
 			       in->hdr.msg.len);
 			goto bad_client;
diff --git a/tools/xenstore/xenstored_watch.c b/tools/xenstore/xenstored_watch.c
index 72927fa9c7..8e3e4f2b61 100644
--- a/tools/xenstore/xenstored_watch.c
+++ b/tools/xenstore/xenstored_watch.c
@@ -125,6 +125,10 @@ void do_watch(struct connection *conn, struct buffered_data *in)
 
 	if (strstarts(vec[0], "@")) {
 		relative = false;
+		if (strlen(vec[0]) > XENSTORE_REL_PATH_MAX) {
+			send_error(conn, EINVAL);
+			return;
+		}
 		/* check if valid event */
 	} else {
 		relative = !strstarts(vec[0], "/");
diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index faa7e5c80f..a815257798 100644
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -319,6 +319,11 @@ static void *xs_talkv(struct xs_handle *h, xs_transaction_t t,
 	for (i = 0; i < num_vecs; i++)
 		msg.len += iovec[i].iov_len;
 
+	if (msg.len > XENSTORE_PAYLOAD_MAX) {
+		errno = E2BIG;
+		return 0;
+	}
+
 	ignorepipe.sa_handler = SIG_IGN;
 	sigemptyset(&ignorepipe.sa_mask);
 	ignorepipe.sa_flags = 0;
diff --git a/tools/xenstore/xsls.c b/tools/xenstore/xsls.c
index cd8e3a9dac..337e87cc5b 100644
--- a/tools/xenstore/xsls.c
+++ b/tools/xenstore/xsls.c
@@ -8,7 +8,7 @@
 #include <sys/ioctl.h>
 #include <termios.h>
 
-#define STRING_MAX PATH_MAX
+#define STRING_MAX XENSTORE_ABS_PATH_MAX+1024
 static int max_width = 80;
 static int desired_width = 60;
 static int show_whole_path = 0;