From d290630d31f4517ab26392d00753d1397f9a4114 Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Wed, 6 Oct 2021 22:31:06 +0100 Subject: [PATCH] Fix crash after re-reading an empty resolv.conf file. If dnsmasq re-reads a resolv file, and it's empty, it will retry after a delay. In the meantime, the old servers from the resolv file have been deleted, but the servers_array doesn't get updated, leading to dangling pointers and crashes. Thanks to Brad Jorsch for finding and analysing this bug. This problem was introduced in 2.86. --- src/dnsmasq.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/src/dnsmasq.c b/src/dnsmasq.c index c7fa024..9516680 100644 --- a/src/dnsmasq.c +++ b/src/dnsmasq.c @@ -1682,6 +1682,11 @@ static void poll_resolv(int force, int do_reload, time_t now) } else { + /* If we're delaying things, we don't call check_servers(), but + reload_servers() may have deleted some servers, rendering the server_array + invalid, so just rebuild that here. Once reload_servers() succeeds, + we call check_servers() above, which calls build_server_array itself. */ + build_server_array(); latest->mtime = 0; if (!warned) { -- 2.20.1