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Change server version from char pointer to char array

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With this change, it is no longer possible that the server version
is deallocated at the very moment it is read. There is still a race,
but it's mostly harmless.
This commit is contained in:
Johan Wikman
2017-06-19 13:40:18 +03:00
parent 32cd28daf2
commit 3e39ec906e
4 changed files with 39 additions and 42 deletions
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49
server/core/server.cc
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@ -131,7 +131,6 @@ SERVER* server_alloc(const char *name, const char *address, unsigned short port,
server->master_id = -1;
server->depth = -1;
server->parameters = NULL;
server->server_string = NULL;
spinlock_init(&server->lock);
server->persistent = persistent;
server->persistmax = 0;
@ -187,7 +186,6 @@ server_free(SERVER *tofreeserver)
/* Clean up session and free the memory */
MXS_FREE(tofreeserver->protocol);
MXS_FREE(tofreeserver->unique_name);
MXS_FREE(tofreeserver->server_string);
server_parameter_free(tofreeserver->parameters);
if (tofreeserver->persistent)
@ -496,10 +494,7 @@ dprintServer(DCB *dcb, const SERVER *server)
MXS_FREE(stat);
dcb_printf(dcb, "\tProtocol: %s\n", server->protocol);
dcb_printf(dcb, "\tPort: %d\n", server->port);
if (server->server_string)
{
dcb_printf(dcb, "\tServer Version: %s\n", server->server_string);
}
dcb_printf(dcb, "\tServer Version: %s\n", server->version_string);
dcb_printf(dcb, "\tNode Id: %ld\n", server->node_id);
dcb_printf(dcb, "\tMaster Id: %ld\n", server->master_id);
if (server->slaves)
@ -1080,28 +1075,35 @@ server_map_status(const char *str)
/**
* Set the version string of the server.
*
* @param server Server to update
* @param string Version string
* @return True if the assignment of the version string was successful, false if
* memory allocation failed.
* @param version Version string
*/
bool server_set_version_string(SERVER* server, const char* string)
void server_set_version_string(SERVER* server, const char* version)
{
bool rval = true;
string = MXS_STRDUP(string);
// There is a race here. The string may be accessed, while we are
// updating it. Thus we take some precautions to ensure that the
// string cannot be completely garbled at any point.
if (string)
size_t old_len = strlen(server->version_string);
size_t new_len = strlen(version);
if (new_len >= MAX_SERVER_VERSION_LEN)
{
char* old = server->server_string;
server->server_string = (char*)string;
MXS_FREE(old);
}
else
{
rval = false;
new_len = MAX_SERVER_VERSION_LEN - 1;
}
return rval;
if (new_len < old_len)
{
// If the new string is shorter, we start by nulling out the
// excess data.
memset(server->version_string + new_len, 0, old_len - new_len);
}
strncpy(server->version_string, version, new_len);
// No null-byte needs to be set. The array starts out as all zeros
// and the above memset adds the necessary null, should the new string
// be shorter than the old.
}
/**
@ -1396,10 +1398,7 @@ static json_t* server_json_attributes(const SERVER* server)
json_object_set_new(attr, CN_STATUS, json_string(stat));
MXS_FREE(stat);
if (server->server_string)
{
json_object_set_new(attr, CN_VERSION_STRING, json_string(server->server_string));
}
json_object_set_new(attr, CN_VERSION_STRING, json_string(server->version_string));
json_object_set_new(attr, "node_id", json_integer(server->node_id));
json_object_set_new(attr, "master_id", json_integer(server->master_id));