[patch] Proposed Patch

empty-resolve.patch (text/plain), 1.21 KB, created by Tango on 2022-09-30 20:45:45 UTC

From d290630d31f4517ab26392d00753d1397f9a4114 Mon Sep 17 00:00:00 2001
From: Simon Kelley <[e-mail]>
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