From: Aurelien DARRAGON <adarragon@haproxy.com>
Date: Wed, 3 Apr 2024 09:41:57 +0000 (+0200)
Subject: BUG/MEDIUM: server/lbprm: fix crash in _srv_set_inetaddr_port()
X-Git-Tag: v3.0-dev7~30
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=837a26ab05350413a63354a8dafc17ac5efc38ef;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: server/lbprm: fix crash in _srv_set_inetaddr_port()

Since faa8c3e ("MEDIUM: lb-chash: Deterministic node hashes based on
server address") the following configuration will cause haproxy to crash:

  backend test1
       mode http
       balance hash int(1)
       server s1 haproxy.org:80

This is because lbprm.update_server_eweight() method is now systematically
called in _srv_set_inetaddr_port() upon srv addr/port change (and with the
above config it happens during startup after initial dns resolution).

However, depending on the chosen lbprm algo, update_server_eweight function
may not be set (it is not a mandatory method, some lb implementations don't
define it).

Thus, using 'balance hash' with map-based hashing or 'balance sticky' will
cause a crash due to a NULL de-reference in _srv_set_inetaddr_port(). To
fix the issue, we first check that the update_server_eweight() method is
set before using it.

No backport needed unless faa8c3e ("MEDIUM: lb-chash: Deterministic node
hashes based on server address") gets backported.
---

diff --git a/src/server.c b/src/server.c
index 52b715bfa0..fc5a45820d 100644
--- a/src/server.c
+++ b/src/server.c
@@ -184,8 +184,10 @@ static void _srv_set_inetaddr_port(struct server *srv,
 	else
 		srv->flags &= ~SRV_F_MAPPORTS;
 
-	/* balancers (chash in particular) may use the addr in their routing decisions */
-	srv->proxy->lbprm.update_server_eweight(srv);
+	if (srv->proxy->lbprm.update_server_eweight) {
+		/* some balancers (chash in particular) may use the addr in their routing decisions */
+		srv->proxy->lbprm.update_server_eweight(srv);
+	}
 
 	if (srv->log_target && srv->log_target->type == LOG_TARGET_DGRAM) {
 		/* server is used as a log target, manually update log target addr for DGRAM */