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>

1 files changed, 4 insertions, 1 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;