Ah, never mind, I built the package incorrectly. It's not a quilt package... :/
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to dnsmasq in Ubuntu. https://bugs.launchpad.net/bugs/2045570 Title: dnsmasq crash when no servers in resolv.conf Status in dnsmasq package in Ubuntu: Fix Released Status in dnsmasq source package in Jammy: In Progress Bug description: [ Impact ] dnsmasq "keeps an eye" on /etc/resolv.conf, and reloads it whenever the file is updated. When that happens and for some reason there were no "nameserver" declarations in the updated file, dnsmasq can crash. Here is a log of a reproducer: $ dig +short @127.0.0.1 ubuntu.com ;; communications error to 127.0.0.1#53: timed out ;; communications error to 127.0.0.1#53: connection refused ;; communications error to 127.0.0.1#53: connection refused ;; no servers could be reached We can see the startup, then when resolv.conf is read again and no nameservers were found, and the crash: Jan 03 13:57:13 j-dnsmasq-2045570 dnsmasq[1507]: started, version 2.86 cachesize 150 Jan 03 13:57:13 j-dnsmasq-2045570 dnsmasq[1507]: DNS service limited to local subnets Jan 03 13:57:13 j-dnsmasq-2045570 dnsmasq[1507]: compile time options: IPv6 GNU-getopt DBus no-UBus i18n IDN2 DHCP DHCPv6 no-Lua TFTP conntrack ipset auth cryptohash DNSSEC loop-detect inotify dumpfile Jan 03 13:57:13 j-dnsmasq-2045570 dnsmasq[1507]: reading /etc/resolv.conf Jan 03 13:57:13 j-dnsmasq-2045570 dnsmasq[1507]: using nameserver 10.0.100.1#53 Jan 03 13:57:13 j-dnsmasq-2045570 dnsmasq[1507]: read /etc/hosts - 7 addresses Jan 03 13:57:13 j-dnsmasq-2045570 systemd[1]: Started dnsmasq - A lightweight DHCP and caching DNS server. Jan 03 13:58:01 j-dnsmasq-2045570 dnsmasq[1507]: no servers found in /etc/resolv.conf, will retry Jan 03 13:58:22 j-dnsmasq-2045570 systemd[1]: dnsmasq.service: Main process exited, code=dumped, status=11/SEGV Jan 03 13:58:22 j-dnsmasq-2045570 systemd[1]: dnsmasq.service: Failed with result 'core-dump'. dnsmasq has provisions for this situation, we can see that in the 13:58:01 message where it says it will retry, but due to this bug, it crashes instead. The problem was introduced[1] in version 2.86, and fixed in 2.87, so only jammy is affected. 1. https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=patch;h=d290630d31f4517ab26392d00753d1397f9a4114;hp=d2ad5dc073aaacaf22b117f16106282a73586803 The commit message says: """ This problem was introduced in 2.86. """ And indeed, I wasn't able to crash 2.80 shipped in focal. [ Test Plan ] It might take a few tries to reproduce the bug, but here is the general outline. Also keep in mind that it's important to use a DNS name that isn't cached already by a previous query. # Create a jammy lxd container lxc launch ubuntu-daily:jammy j-dnsmasq-2045570 # Enter the container lxc shell j-dnsmasq-2045570 # From now on, all commands should be executed in the container. # Install dnsmasq, and disable systemd-resolved apt update && apt install -y dnsmasq # Disable systemd-resolved, and start dnsmasq systemctl disable --now systemd-resolved systemctl enable --now dnsmasq # In one terminal inside the container, watch the dnsmasq logs: journalctl -u dnsmasq.service -f # In another terminal, remove /etc/resolv.conf and create a new one, empty rm /etc/resolv.conf echo "nameserver 1.1.1.1" > /etc/resolv.conf # restart dnsmasq systemctl restart dnsmasq.service # Perform a dns query dig @127.0.0.1 +short linux.com # Comment the namserver directive in resolv.conf echo "#nameserver 1.1.1.1" > /etc/resolv.conf # Observe in the dnsmasq logs that it notices the change with a message like: Jan 03 14:14:51 j-dnsmasq-2045570 dnsmasq[2274]: no servers found in /etc/resolv.conf, will retry # Perform a *different* DNS query dig @127.0.0.1 +short ubuntu.com # Observe in the dnsmasq logs that it crashes. Jan 03 13:58:22 j-dnsmasq-2045570 systemd[1]: dnsmasq.service: Main process exited, code=dumped, status=11/SEGV Jan 03 13:58:22 j-dnsmasq-2045570 systemd[1]: dnsmasq.service: Failed with result 'core-dump'. If it doesn't crash right away, repeat these steps a few times, but using a different domain name each time: - add "nameserver 127.0.0.1" to /etc/resolv.conf - observe that dnsmasq notices the change to the file - perform a query for some random domain using "dig @127.0.0.1 +short <domain-of-your-choosing>" - remove "nameserver" from /etc/resolv.conf, observe that dnsmasq noticed the change - perform a query for another random domain The fixed version from proposed will not crash. That last query with no "nameserver" lines in resolv.conf won't work, but it won't crash the server. [ Where problems could occur ] This is doing some pointer/memory manipulation that could introduce memory leaks or other crashes. In fact, this is exactly what happened in the 2.86 release, which, and I quote, "Major rewrite of the DNS server and domain handling code. This should be largely transparent, but it drastically improves performance and reduces memory foot- print"[2]. 2.88 was then released with the fix used in this SRU (the commit is also in the 2.87 tag, but the upstream release notes only mention it in 2.88). 2. https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=blob;f=CHANGELOG;h=2ce53a81079810ae43588607f43851dabb5db38d;hb=HEAD#l224 [ Other Info ] Not at this time. [ Original description ] upstream discussion: https://lists.thekelleys.org.uk/pipermail/dnsmasq- discuss/2022q3/016563.html in my journal, my dns service crash and restart just after: Dec 04 17:18:38 dnsmasq[199333]: no servers found in /run/NetworkManager/no-stub-resolv.conf, will retry oops report: https://errors.ubuntu.com/oops/29cf5e2e-92b1-11ee-9bdf- fa163ec44ecd ubuntu jammy, dnsmasq-base 2.86-1.1ubuntu0.3 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/2045570/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
