From: Christopher Faulet <cfaulet@haproxy.com>
Date: Wed, 19 Jun 2019 08:50:38 +0000 (+0200)
Subject: BUG/MEDIUM: lb_fwlc: Don't test the server's lb_tree from outside the lock
X-Git-Tag: v2.1-dev1~70
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1ae2a8878170ded922f2c4d32b6704af7689bbfd;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: lb_fwlc: Don't test the server's lb_tree from outside the lock

In the function fwlc_srv_reposition(), the server's lb_tree is tested from
outside the lock. So it is possible to remove it after the test and then call
eb32_insert() in fwlc_queue_srv() with a NULL root pointer, which is
invalid. Moving the test in the scope of the lock fixes the bug.

This issue was reported on Github, issue #126.

This patch must be backported to 2.0, 1.9 and 1.8.
---

diff --git a/src/lb_fwlc.c b/src/lb_fwlc.c
index 174dc67e69..5fa8173998 100644
--- a/src/lb_fwlc.c
+++ b/src/lb_fwlc.c
@@ -66,12 +66,11 @@ static inline void fwlc_queue_srv(struct server *s)
  */
 static void fwlc_srv_reposition(struct server *s)
 {
-	if (!s->lb_tree)
-		return;
-
 	HA_SPIN_LOCK(LBPRM_LOCK, &s->proxy->lbprm.lock);
-	fwlc_dequeue_srv(s);
-	fwlc_queue_srv(s);
+	if (s->lb_tree) {
+		fwlc_dequeue_srv(s);
+		fwlc_queue_srv(s);
+	}
 	HA_SPIN_UNLOCK(LBPRM_LOCK, &s->proxy->lbprm.lock);
 }