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Patch-Source: https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=d290630d31f4517ab26392d00753d1397f9a4114 (upstream)
--
From d290630d31f4517ab26392d00753d1397f9a4114 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
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
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