From: Olivier Houchard <ohouchard@haproxy.com>
Date: Mon, 1 Jun 2026 13:52:21 +0000 (+0200)
Subject: BUG/MEDIUM: leastconn: Unlock the write lock on allocation failure
X-Git-Tag: v3.4.0~27
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c0aa9f01f113c2b61794107ee1b79e28a59bd896;p=thirdparty%2Fhaproxy.git

BUG/MEDIUM: leastconn: Unlock the write lock on allocation failure

When we fail to allocate a new tree element, we're still holding the
write lock, so we should do an write unlock, not a read unlock, or the
lock will get corrupted and most likely this will end in a deadlock.

This should be backported up to 3.2.
---

diff --git a/src/lb_fwlc.c b/src/lb_fwlc.c
index 6657d4c1e..6c1cd13e0 100644
--- a/src/lb_fwlc.c
+++ b/src/lb_fwlc.c
@@ -437,7 +437,7 @@ static void fwlc_srv_reposition(struct server *s)
 		tree_elt = fwlc_alloc_tree_elt(s->proxy, allocated_elt);
 		if (tree_elt == NULL) {
 			/* We failed to allocate memory, just try again later */
-			HA_RWLOCK_RDUNLOCK(LBPRM_LOCK, &s->proxy->lbprm.lock);
+			HA_RWLOCK_WRUNLOCK(LBPRM_LOCK, &s->proxy->lbprm.lock);
 			_HA_ATOMIC_STORE(&s->lb_lock, 0);
 			if (s->requeue_tasklet)
 				tasklet_wakeup(s->requeue_tasklet);