We've long had double free's in the shutdown code, and one of the causes was
trying to clear up the client args in the callback structures. There is code
that I added in all 3 branches that loops through all the callbacks and clears
a given client arg from any callback that is using it. This is called when a
session is closed, and during the shutdown cleanup.
Unfortunately, a slight coding error reduced the utility of this routine, as
it will only check callbacks for the first callback type. This patch adds a
little debug and initializes the inner loop counter properly so that all
callback types will be cleared.
Without this patch, a subagent which has successfully connected to the master
agent will encounter a double-free during shutdown, and will most likely
crash. Not as critical as a crash during normal operation, but none-the less..
diff -u -p -r5.6.2.2 -r5.6.2.3
--- snmplib/callback.c 21 Apr 2005 14:52:50 -0000 5.6.2.2
+++ snmplib/callback.c 17 Oct 2005 22:24:37 -0000 5.6.2.3
@@ -348,13 +348,14 @@ netsnmp_callback_clear_client_arg(void *
struct snmp_gen_callback *scp = NULL;
int rc = 0;
- for (; i < MAX_CALLBACK_IDS; i++) {
+ for (; i < MAX_CALLBACK_IDS; i++,j=0) {
for (; j < MAX_CALLBACK_SUBIDS; j++) {
scp = thecallbacks[i][j];
while (scp != NULL) {
if ((NULL != scp->sc_callback) &&
(scp->sc_client_arg != NULL) &&
(scp->sc_client_arg == ptr)) {
+ DEBUGMSGTL(("9:callback", " clearing %p at [%d,%d]\n",
ptr, i, j)); scp->sc_client_arg = NULL;
++rc;
}
@@ -402,6 +403,7 @@ clear_callback(void)
*/
tmp_arg = scp->sc_client_arg;
scp->sc_client_arg = NULL;
+ DEBUGMSGTL(("9:callback", " freeing %p at [%d,%d]\n",
tmp_arg, i, j)); (void)netsnmp_callback_clear_client_arg(tmp_arg, i, j);
free(tmp_arg);
}
--
Robert Story; NET-SNMP Junkie
Support: <http://www.net-snmp.org/> <irc://irc.freenode.net/#net-snmp>
Archive: <http://sourceforge.net/mailarchive/forum.php?forum=net-snmp-coders>
You are lost in a twisty maze of little standards, all different.
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