Unbound 1.20 crashes in less than one hour, in libevent

[bortzmeyer]

Describe the bug

I upgraded to Unbound 1.20 (a small resolver). After that, it crashes in less than one hour.

To reproduce Steps to reproduce the behavior:

1. Run unbound
2. Wait

Expected behavior No crash

System:

• Unbound version: 1.20.0
• OS: ArchLinux, upgraded today, Linux kernel 6.8.9
• unbound -V output:

Version 1.20.0

Configure line: --prefix=/usr --sysconfdir=/etc --localstatedir=/var --sbindir=/usr/bin --disable-rpath --enable-dnscrypt --enable-dnstap --enable-pie --enable-relro-now --enable-subnet --enable-systemd --enable-tfo-client --enable-tfo-server --enable-cachedb --with-libhiredis --with-conf-file=/etc/unbound/unbound.conf --with-pidfile=/run/unbound.pid --with-rootkey-file=/etc/trusted-key.key --with-libevent --with-libnghttp2 --with-pyunbound
Linked libs: libevent 2.1.12-stable (it uses epoll), OpenSSL 3.3.0 9 Apr 2024
Linked modules: dns64 cachedb subnetcache respip validator iterator
DNSCrypt feature available
TCP Fastopen feature available

BSD licensed, see LICENSE in source package for details.
Report bugs to [email protected] or https://github.com/NLnetLabs/unbound/issues

Additional information

Downgrading to 1.19.3 apparently solved the problem. I also tried a 1.20 without --with-libevent but it also crashed.

A core dump is produced:

% gdb /usr/sbin/unbound.ORIG unbound-core
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Reading symbols from /usr/sbin/unbound.ORIG...

This GDB supports auto-downloading debuginfo from the following URLs:
  <https://debuginfod.archlinux.org>
Enable debuginfod for this session? (y or [n]) 
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To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
(No debugging symbols found in /usr/sbin/unbound.ORIG)
[New LWP 35395]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Core was generated by `/usr/bin/unbound -d -p'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007404a8942976 in ?? () from /usr/lib/libevent-2.1.so.7
(gdb) where
#0  0x00007404a8942976 in ?? () from /usr/lib/libevent-2.1.so.7
#1  0x00007404a894a344 in event_base_loop () from /usr/lib/libevent-2.1.so.7
#2  0x0000597888a39a06 in ?? ()
#3  0x0000597888967dd2 in ?? ()
#4  0x000059788897eb8e in ?? ()
#5  0x00005978889602ea in ?? ()
#6  0x00007404a8039c88 in ?? () from /usr/lib/libc.so.6
#7  0x00007404a8039d4c in __libc_start_main () from /usr/lib/libc.so.6
#8  0x0000597888960375 in ?? ()
(gdb) quit