[Bug 1809438] Re: systemd-resolved segfaults

[Danny Brugman]

I seem to be affected by the same issue. I get regular DNS query time-
outs coinciding with a lot of the following log messages (syslog):

systemd-resolved[1119]: Server returned error NXDOMAIN, mitigating
potential DNS violation DVE-2018-0001, retrying transaction with reduced
feature level UDP.

Eventually systemd-resolved crashes. This happens more frequently (/or
only) when connected to wifi.

Trace extracted from an Apport crash report (cause was a segmentation
fault):

#0  0x00007efeaa3c62ed in sd_event_source_unref (p=0x1b01030036100326) at ../src/libsystemd/sd-event/sd-event.c:1912
        __PRETTY_FUNCTION__ = "sd_event_source_unref"
#1  0x0000561894e7f162 in dns_query_stop (q=q at entry=0x5618967255b0) at ../src/resolve/resolved-dns-query.c:336
        c = <optimized out>
        __PRETTY_FUNCTION__ = "dns_query_stop"
#2  0x0000561894e7f1d0 in dns_query_complete (q=0x5618967255b0, state=<optimized out>) at ../src/resolve/resolved-dns-query.c:528
        __PRETTY_FUNCTION__ = "dns_query_complete"
#3  0x0000561894e7f33f in on_query_timeout (s=<optimized out>, usec=<optimized out>, userdata=<optimized out>) at ../src/resolve/resolved-dns-query.c:539
        q = <optimized out>
        __PRETTY_FUNCTION__ = "on_query_timeout"
#4  0x00007efeaa3ceb76 in source_dispatch (s=s at entry=0x561896722680) at ../src/libsystemd/sd-event/sd-event.c:3201
        saved_type = SOURCE_TIME_BOOTTIME
        r = <optimized out>
        __PRETTY_FUNCTION__ = "source_dispatch"
        __func__ = "source_dispatch"
#5  0x00007efeaa3ceef1 in sd_event_dispatch (e=e at entry=0x5618966cfcd0) at ../src/libsystemd/sd-event/sd-event.c:3634
        ref = <optimized out>
        p = <optimized out>
        r = <optimized out>
        __PRETTY_FUNCTION__ = "sd_event_dispatch"
#6  0x00007efeaa3d0928 in sd_event_run (e=e at entry=0x5618966cfcd0, timeout=timeout at entry=18446744073709551615) at ../src/libsystemd/sd-event/sd-event.c:3692
        r = 1
        __PRETTY_FUNCTION__ = "sd_event_run"
#7  0x00007efeaa3d0b4f in sd_event_loop (e=0x5618966cfcd0) at ../src/libsystemd/sd-event/sd-event.c:3714
        ref = 0x5618966cfcd0
        r = <optimized out>
        __PRETTY_FUNCTION__ = "sd_event_loop"
#8  0x0000561894e5a22a in run (argv=<optimized out>, argc=<optimized out>) at ../src/resolve/resolved.c:84
        notify_stop = 0x561894ea3d70 "STOPPING=1\nSTATUS=Shutting down..."

Log statement from the kernel log:

traps: systemd-resolve[1162] general protection fault ip:7efeaa3c62ed
sp:7ffef7d6f1b0 error:0 in libsystemd-shared-245.so[7efeaa39e000+174000]

(Although the trace started with a notify_stop, the system was not
shutdown at the time)

Other details:

Release: Ubuntu 20.04.01 (amd64)
Systemd package version: 245.4-4ubuntu3.4

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https://bugs.launchpad.net/bugs/1809438

Title:
  systemd-resolved segfaults

Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  I regularly (once almost every hour) get segfaults resported in
  systemd-resolved. The syslog is not always the same:

  Dec 21 06:59:21 marshall kernel: [988042.071003] systemd-resolve[15794]: segfault at e60e8ad514 ip 000000e60e8ad514 sp 00007ffe0376e748 error 14 in systemd-resolved[556f74bcf000+59000]
  Dec 21 06:59:21 marshall systemd[1]: systemd-resolved.service: Main process exited, code=dumped, status=11/SEGV
  Dec 21 06:59:21 marshall systemd[1]: systemd-resolved.service: Failed with result 'core-dump'.

  Dec 21 08:17:47 marshall kernel: [992748.334333] systemd-resolve[16943]: segfault at 2a11d9b0 ip 00007f4810f5ad26 sp 00007fff544db0f0 error 4 in libsystemd-shared-237.so[7f4810e1f000+1b5000]
  Dec 21 08:17:47 marshall systemd[1]: systemd-resolved.service: Main process exited, code=dumped, status=11/SEGV
  Dec 21 08:17:47 marshall systemd[1]: systemd-resolved.service: Failed with result 'core-dump'.

  Dec 21 06:22:45 marshall systemd-resolved[15727]: Assertion 'p->n_ref > 0' failed at ../src/resolve/resolved-dns-packet.c:210, function dns_packet_unref(). Aborting.
  Dec 21 06:22:45 marshall systemd[1]: systemd-resolved.service: Main process exited, code=dumped, status=6/ABRT
  Dec 21 06:22:45 marshall systemd[1]: systemd-resolved.service: Failed with result 'core-dump'.

  Dec 21 06:17:46 marshall systemd-resolved[15662]: Assertion 'DNS_TRANSACTION_IS_LIVE(q->state)' failed at ../src/resolve/resolved-dns-query.c:540, function dns_query_complete(). Aborting.
  Dec 21 06:17:46 marshall systemd[1]: systemd-resolved.service: Main process exited, code=dumped, status=6/ABRT
  Dec 21 06:17:46 marshall systemd[1]: systemd-resolved.service: Failed with result 'core-dump'.

  The system in question uses dnsmasq as local DNS server. Logging that is probably unrelated, but often seen (possibly due to the setup with dnsmasq) is:
  dec 21 10:22:00 marshall systemd-resolved[3183]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
  dec 21 10:17:15 marshall systemd-resolved[3183]: Using degraded feature set (TCP) for DNS server 127.0.0.1.

  
  # dpkg --status systemd
  Package: systemd
  Installed-Size: 12444
  Maintainer: Ubuntu Developers <ubuntu-devel-discuss at lists.ubuntu.com>
  Architecture: amd64
  Multi-Arch: foreign
  Version: 237-3ubuntu10.9

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