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[snmpd]: Fix snmpd crash possible when snmp agent takes too long to r…
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…espond. (#3454)

Patch from source-forge: net-snmp.
Crash due to stale memory access.
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@renukamanavalan @lguohan
renukamanavalan authored and lguohan committed Sep 14, 2019
1 parent 9cde0fc commit cb81e3a
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211 changes: 211 additions & 0 deletions ...dfsg/0006-From-Jiri-Cervenka-snmpd-Fixed-agentx-crashing-and-or-freezing-on-timeout.patch
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@@ -0,0 +1,211 @@
From a5782d0673044ad0c621daed7975f53238bb038e Mon Sep 17 00:00:00 2001
From: Renuka Manavalan <remanava@microsoft.com>
Date: Tue, 10 Sep 2019 17:51:45 +0000
Subject: [PATCH] Patch from SourceForge: net-snmp commit #793d59 Avoids snmpd
crash when sub agent timesout.

---
agent/mibgroup/agentx/master_admin.c | 1 +
agent/snmp_agent.c | 81 ++++++++++++++++++----------
include/net-snmp/agent/snmp_agent.h | 5 ++
3 files changed, 60 insertions(+), 27 deletions(-)

diff --git a/agent/mibgroup/agentx/master_admin.c b/agent/mibgroup/agentx/master_admin.c
index 4dc1aa7..8c1d194 100644
--- a/agent/mibgroup/agentx/master_admin.c
+++ b/agent/mibgroup/agentx/master_admin.c
@@ -158,6 +158,7 @@ close_agentx_session(netsnmp_session * session, int sessid)
for (sp = session->subsession; sp != NULL; sp = sp->next) {

if (sp->sessid == sessid) {
+ netsnmp_remove_delegated_requests_for_session(sp);
unregister_mibs_by_session(sp);
unregister_index_by_session(sp);
unregister_sysORTable_by_session(sp);
diff --git a/agent/snmp_agent.c b/agent/snmp_agent.c
index b96d650..7cacd1a 100644
--- a/agent/snmp_agent.c
+++ b/agent/snmp_agent.c
@@ -1409,6 +1409,7 @@ init_agent_snmp_session(netsnmp_session * session, netsnmp_pdu *pdu)
asp->treecache_num = -1;
asp->treecache_len = 0;
asp->reqinfo = SNMP_MALLOC_TYPEDEF(netsnmp_agent_request_info);
+ asp->flags = SNMP_AGENT_FLAGS_NONE;
DEBUGMSGTL(("verbose:asp", "asp %p reqinfo %p created\n",
asp, asp->reqinfo));

@@ -1457,6 +1458,9 @@ netsnmp_check_for_delegated(netsnmp_agent_session *asp)

if (NULL == asp->treecache)
return 0;
+
+ if (asp->flags & SNMP_AGENT_FLAGS_CANCEL_IN_PROGRESS)
+ return 0;

for (i = 0; i <= asp->treecache_num; i++) {
for (request = asp->treecache[i].requests_begin; request;
@@ -1535,39 +1539,48 @@ int
netsnmp_remove_delegated_requests_for_session(netsnmp_session *sess)
{
netsnmp_agent_session *asp;
- int count = 0;
+ int total_count = 0;

for (asp = agent_delegated_list; asp; asp = asp->next) {
/*
* check each request
*/
+ int i;
+ int count = 0;
netsnmp_request_info *request;
- for(request = asp->requests; request; request = request->next) {
- /*
- * check session
- */
- netsnmp_assert(NULL!=request->subtree);
- if(request->subtree->session != sess)
- continue;
+ for (i = 0; i <= asp->treecache_num; i++) {
+ for (request = asp->treecache[i].requests_begin; request;
+ request = request->next) {
+ /*
+ * check session
+ */
+ netsnmp_assert(NULL!=request->subtree);
+ if(request->subtree->session != sess)
+ continue;

- /*
- * matched! mark request as done
- */
- netsnmp_request_set_error(request, SNMP_ERR_GENERR);
- ++count;
+ /*
+ * matched! mark request as done
+ */
+ netsnmp_request_set_error(request, SNMP_ERR_GENERR);
+ ++count;
+ }
+ }
+ if (count) {
+ asp->flags |= SNMP_AGENT_FLAGS_CANCEL_IN_PROGRESS;
+ total_count += count;
}
}

/*
* if we found any, that request may be finished now
*/
- if(count) {
+ if(total_count) {
DEBUGMSGTL(("snmp_agent", "removed %d delegated request(s) for session "
- "%8p\n", count, sess));
- netsnmp_check_outstanding_agent_requests();
+ "%8p\n", total_count, sess));
+ netsnmp_check_delegated_requests();
}

- return count;
+ return total_count;
}

int
@@ -2739,19 +2752,11 @@ handle_var_requests(netsnmp_agent_session *asp)
return final_status;
}

-/*
- * loop through our sessions known delegated sessions and check to see
- * if they've completed yet. If there are no more delegated sessions,
- * check for and process any queued requests
- */
void
-netsnmp_check_outstanding_agent_requests(void)
+netsnmp_check_delegated_requests(void)
{
netsnmp_agent_session *asp, *prev_asp = NULL, *next_asp = NULL;

- /*
- * deal with delegated requests
- */
for (asp = agent_delegated_list; asp; asp = next_asp) {
next_asp = asp->next; /* save in case we clean up asp */
if (!netsnmp_check_for_delegated(asp)) {
@@ -2790,6 +2795,23 @@ netsnmp_check_outstanding_agent_requests(void)
prev_asp = asp;
}
}
+}
+
+
+/*
+ * loop through our sessions known delegated sessions and check to see
+ * if they've completed yet. If there are no more delegated sessions,
+ * check for and process any queued requests
+ */
+void
+netsnmp_check_outstanding_agent_requests(void)
+{
+ netsnmp_agent_session *asp;
+
+ /*
+ * deal with delegated requests
+ */
+ netsnmp_check_delegated_requests();

/*
* if we are processing a set and there are more delegated
@@ -2819,7 +2841,8 @@ netsnmp_check_outstanding_agent_requests(void)

netsnmp_processing_set = netsnmp_agent_queued_list;
DEBUGMSGTL(("snmp_agent", "SET request remains queued while "
- "delegated requests finish, asp = %8p\n", asp));
+ "delegated requests finish, asp = %8p\n",
+ agent_delegated_list));
break;
}
#endif /* NETSNMP_NO_WRITE_SUPPORT */
@@ -2880,6 +2903,10 @@ check_delayed_request(netsnmp_agent_session *asp)
case SNMP_MSG_GETBULK:
case SNMP_MSG_GETNEXT:
netsnmp_check_all_requests_status(asp, 0);
+ if (asp->flags & SNMP_AGENT_FLAGS_CANCEL_IN_PROGRESS) {
+ DEBUGMSGTL(("snmp_agent","canceling next walk for asp %p\n", asp));
+ break;
+ }
handle_getnext_loop(asp);
if (netsnmp_check_for_delegated(asp) &&
netsnmp_check_transaction_id(asp->pdu->transid) !=
diff --git a/include/net-snmp/agent/snmp_agent.h b/include/net-snmp/agent/snmp_agent.h
index aad8837..43f4fff 100644
--- a/include/net-snmp/agent/snmp_agent.h
+++ b/include/net-snmp/agent/snmp_agent.h
@@ -32,6 +32,9 @@ extern "C" {
#define SNMP_MAX_PDU_SIZE 64000 /* local constraint on PDU size sent by agent
* (see also SNMP_MAX_MSG_SIZE in snmp_api.h) */

+#define SNMP_AGENT_FLAGS_NONE 0x0
+#define SNMP_AGENT_FLAGS_CANCEL_IN_PROGRESS 0x1
+
/*
* If non-zero, causes the addresses of peers to be logged when receptions
* occur.
@@ -205,6 +208,7 @@ extern "C" {
int treecache_num; /* number of current cache entries */
netsnmp_cachemap *cache_store;
int vbcount;
+ int flags;
} netsnmp_agent_session;

/*
@@ -240,6 +244,7 @@ extern "C" {
int init_master_agent(void);
void shutdown_master_agent(void);
int agent_check_and_process(int block);
+ void netsnmp_check_delegated_requests(void);
void netsnmp_check_outstanding_agent_requests(void);

int netsnmp_request_set_error(netsnmp_request_info *request,
--
2.17.1

1 change: 1 addition & 0 deletions src/snmpd/patch-5.7.3+dfsg/series
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,3 +2,4 @@
0002-at.c-properly-check-return-status-from-realloc.-Than.patch
0003-CHANGES-BUG-2743-snmpd-crashes-when-receiving-a-GetN.patch
0004-Disable-SNMPv1.patch
0006-From-Jiri-Cervenka-snmpd-Fixed-agentx-crashing-and-or-freezing-on-timeout.patch

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