From 762b2cb8dc3eb46fb8f348f3dd04611f049a32e2 Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze@samba.org>
Date: Wed, 20 Dec 2017 08:25:19 +0100
Subject: [PATCH] g_lock: fix cleanup of stale entries in g_lock_trylock()

g_lock_trylock() always incremented the counter 'i', even after cleaning a stale
entry at position 'i', which means it skipped checking for a conflict against
the new entry at position 'i'.

As result a process could get a write lock, while there're still
some read lock holders. Once we get into that problem, also more than
one write lock are possible.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13195

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Wed Dec 20 20:31:48 CET 2017 on sn-devel-144
(similar to commit 576fb4fb5dc506bf55e5cf87973999dca444149b)
---
 source3/lib/g_lock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/source3/lib/g_lock.c b/source3/lib/g_lock.c
index 198fe56..2e8f232 100644
--- a/source3/lib/g_lock.c
+++ b/source3/lib/g_lock.c
@@ -301,9 +301,11 @@ static NTSTATUS g_lock_trylock(struct db_record *rec, struct server_id self,
 		}
 	}
 
-	for (i=0; i<num_locks; i++) {
+	i=0;
 
+	while (i < num_recs) {
 		if (i == my_lock) {
+			i++;
 			continue;
 		}
 
@@ -329,7 +331,9 @@ static NTSTATUS g_lock_trylock(struct db_record *rec, struct server_id self,
 			locks[i] = locks[num_locks-1];
 			num_locks -= 1;
 			modified = true;
+			continue;
 		}
+		i++;
 	}
 
 	if (my_lock >= num_locks) {
-- 
1.9.1