From bd8dd841e5383ecec1661d94bddb0fa2ef515842 Mon Sep 17 00:00:00 2001
From: Amaury Denoyelle <adenoyelle@haproxy.com>
Date: Wed, 4 Aug 2021 11:20:05 +0200
Subject: [PATCH] BUG/MINOR: server: remove srv from px list on CLI 'add
 server' error

If an error occured during the CLI 'add server' handler, the newly
created server must be removed from the proxy list if already inserted.
Currently, this can happen on the extremely rare error during server id
generation if there is no id left.

The removal operation is not thread-safe, it must be conducted before
releasing the thread isolation.

This can be backported up to 2.4. Please note that dynamic server track
is not implemented in 2.4, so the release_server_track invocation must
be removed for the backport to prevent a compilation error.
---
 src/server.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/server.c b/src/server.c
index d5fceb9a7..22d0fff68 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4589,8 +4589,23 @@ static int cli_parse_add_server(char **args, char *payload, struct appctx *appct
 	return 0;
 
 out:
-	if (srv && srv->track)
-		release_server_track(srv);
+	if (srv) {
+		if (srv->track)
+			release_server_track(srv);
+
+		/* remove the server from the proxy linked list */
+		if (be->srv == srv) {
+			be->srv = srv->next;
+		}
+		else {
+			struct server *prev;
+			for (prev = be->srv; prev && prev->next != srv; prev = prev->next)
+				;
+			if (prev)
+				prev->next = srv->next;
+		}
+
+	}
 
 	thread_release();