[Dnsmasq-discuss] BUG Segfault when adding ethers entry via dBus and no dhcp-range is configured - debian version 2.89-1

Tue Dec 3 10:56:29 UTC 2024

Hi all,

I have tested with the latest git version (compiled it as close as possible from what the debian package uses), and the crash is still there.
As you can see in the logs:
déc. 03 11:48:07 debian12-dev dnsmasq[105797]: started, version 2.90deb2-48-g6c9bc01 cachesize 150
déc. 03 11:48:07 debian12-dev dnsmasq[105797]: compile time options: IPv6 GNU-getopt DBus no-UBus no-i18n IDN2 DHCP DHCPv6 Lua TFTP conntra>
déc. 03 11:48:07 debian12-dev dnsmasq[105797]: DBus support enabled: connected to system bus
déc. 03 11:48:07 debian12-dev dnsmasq-dhcp[105797]: IPv6 router advertisement enabled
déc. 03 11:48:07 debian12-dev dnsmasq[105797]: reading /etc/resolv.conf
déc. 03 11:48:07 debian12-dev dnsmasq[105797]: using nameserver 192.168.122.1#53
déc. 03 11:48:07 debian12-dev dnsmasq[105797]: cleared cache
déc. 03 11:48:07 debian12-dev systemd[1]: Started dnsmasq at simple.service - dnsmasq (simple) - A lightweight DHCP and caching DNS server.
déc. 03 11:48:39 debian12-dev systemd[1]: Reloading dnsmasq at simple.service - dnsmasq (simple) - A lightweight DHCP and caching DNS server...
déc. 03 11:48:39 debian12-dev dnsmasq[105797]: cleared cache
déc. 03 11:48:39 debian12-dev systemd[1]: Reloaded dnsmasq at simple.service - dnsmasq (simple) - A lightweight DHCP and caching DNS server.
déc. 03 11:48:39 debian12-dev systemd[1]: dnsmasq at simple.service: Main process exited, code=killed, status=11/SEGV
déc. 03 11:48:39 debian12-dev systemd[1]: dnsmasq at simple.service: Failed with result 'signal'.

Best Regards

________________________________________
De : Dnsmasq-discuss <dnsmasq-discuss-bounces at lists.thekelleys.org.uk> de la part de Lou Lecrivain via Dnsmasq-discuss <dnsmasq-discuss at lists.thekelleys.org.uk>
Envoyé : lundi 2 décembre 2024 11:01
À : dnsmasq-discuss at lists.thekelleys.org.uk <dnsmasq-discuss at lists.thekelleys.org.uk>
Objet : [!!ACHTUNG extern!!] - Re: [Dnsmasq-discuss] BUG Segfault when adding ethers entry via dBus and no dhcp-range is configured - debian version 2.89-1

Re,

On my side, what I have observed is that this bug occurs when there are NO dhcp-range statements at all.
The bug does not happen if there are dhcp-range statement(s) present.

And yes, I think so too, that maybe a check is missing somewhere... but I guess you know the source code better than I do.

I'll test with latest stable version and report back.

hth,
BR

________________________________________
De : Dnsmasq-discuss <dnsmasq-discuss-bounces at lists.thekelleys.org.uk> de la part de Simon Kelley <simon at thekelleys.org.uk>
Envoyé : dimanche 1 décembre 2024 23:17
À : dnsmasq-discuss at lists.thekelleys.org.uk <dnsmasq-discuss at lists.thekelleys.org.uk>
Objet : [!!ACHTUNG extern!!] - Re: [Dnsmasq-discuss] BUG Segfault when adding ethers entry via dBus and no dhcp-range is configured - debian version 2.89-1

I'd be curious about that too, but I think the fundamental problem here
is probably that the Dbus interface code doesn't take into account that
the DHCP subsystem may not have been  initialised at all: If there's no
--dhcp-range statement at all, then it won't have been initialised, and
the dBus lease-update method should check for that and return an error.

Lou, could you clarify if this bug occurs when there are NO dhcp-range
statements, or just no dhcp-range statements for the subnet in the
ethersfile. That's not quite clear from your bug report.

Cheers,

Simon

On 12/1/24 18:49, jay at gr-oss.io wrote:
> Hi Lou,
>
> I'd be curious if https://thekelleys.org.uk/gitweb/?
> p=dnsmasq.git;a=commitdiff;h=f006be7842104a9f86fbf419326b7aad08ade61d
> could fix your issue. It corrected a similarly-presenting issue in
> OpenStack Ironic's updating of DHCP options recently.
>
> It hasn't been added to any releases yet, so you will need to build it
> locally. We have a bash function here: https://github.com/openstack/
> ironic/blob/360e21124c2369174d7b38fbb8edf581e85f52e0/devstack/lib/
> ironic#L3565
> which builds the newer version for our CI, you're welcome to borrow it
> -- although I'd suggest installing to /opt
> or /usr/local unless you don't mind making your package manager angry :D.
> -
> Jay Faulkner
>
> On 11/29/24 4:22 AM, Lou Lecrivain via Dnsmasq-discuss <dnsmasq-
> discuss at lists.thekelleys.org.uk> wrote:
>> Hello,
>>
>> I'd like to make a bug report following an issue discovered via
>> Proxmox VE #5949 (https://bugzilla.proxmox.com/show_bug.cgi?id=5949
>> <https:// bugzilla.proxmox.com/show_bug.cgi?id=5949>). This happens on
>> debian dnsmasq package version 2.89-1. I have not yet tested on latest
>> release / dev, but if you wish, I can try to reproduce on it too.
>>
>> How to reproduce:
>>
>>   *
>>     general dnsmasq configuration
>>   *
>>     configure interface (not sure this is mandatory for reproduction)
>>   *
>>     configure dhcp-option for a subnet (same comment)
>>   *
>>     do NOT create the dhcp-range in the config file
>>   *
>>     write ethers file with an entry that's in the subnet without dhcp-
>> range
>>   *
>>     ask for reload via systemd
>>   *
>>     update lease via dBus, see code with link below
>>     https://git.proxmox.com/?p=pve-network.git;a=blob;f=src/PVE/Network/
>>     SDN/Dhcp/
>>     Dnsmasq.pm;h=ae52d3199e0fc51fd1401d7dd78085ad730e5588;hb=refs/heads/
>>     master#l41 <https://git.proxmox.com/?p=pve-network.git;a=blob;f=src/
>>     PVE/Network/SDN/Dhcp/
>>     Dnsmasq.pm;h=ae52d3199e0fc51fd1401d7dd78085ad730e5588;hb=refs/heads/
>>     master#l41>
>>   *
>>     segfault happens at this point
>>
>> Restarting manually via systemctl after the crash does not yields any
>> further errors.
>>
>> The crash/segmentation fault precisely happens just right after reload
>> is triggered. I have the following message in journalctl (sorry for
>> the french!):
>> nov. 28 12:49:38 debian12-dev systemd[1]: Starting
>> dnsmasq at simple.service - dnsmasq (simple) - A lightweight DHCP and
>> caching DNS server>
>> nov. 28 12:49:38 debian12-dev dnsmasq[10598]: demarré, version 2.89
>> (taille de cache 150)
>> nov. 28 12:49:38 debian12-dev dnsmasq[10598]: options à la
>> compilation : IPv6 GNU-getopt DBus no-UBus i18n IDN2 DHCP DHCPv6 no-
>> Lua TFTP >
>> nov. 28 12:49:38 debian12-dev dnsmasq[10598]: Support DBus autorisé :
>> connecté au bus système
>> nov. 28 12:49:38 debian12-dev dnsmasq-dhcp[10598]: annonces de routeur
>> IPv6 activées
>> nov. 28 12:49:38 debian12-dev dnsmasq[10598]: Lecture de /etc/resolv.conf
>> nov. 28 12:49:38 debian12-dev dnsmasq[10598]: utilise le serveur de
>> nom 192.168.122.1#53
>> nov. 28 12:49:38 debian12-dev dnsmasq[10598]: cache vidé
>> nov. 28 12:49:39 debian12-dev systemd[1]: Started
>> dnsmasq at simple.service - dnsmasq (simple) - A lightweight DHCP and
>> caching DNS server.
>> nov. 28 12:49:44 debian12-dev systemd[1]: dnsmasq at simple.service: Main
>> process exited, code=killed, status=11/SEGV
>>
>> Don't hesitate to get back to me if you need further details.
>>
>> Best regards
>> --
>> Lou Lécrivain
>> Systems & Network engineer
>> WDZ GmbH
>> 📧 lou.lecrivain at wdz.de <mailto:lou.lecrivain at wdz.de>
>> <https://outlook.office.com/bookwithme/
>> user/347bbab3d47d435cadf7ceea954b35d8 at wdz.de?anonymous&ep=signature>
>> Book a meeting with me <https://outlook.office.com/bookwithme/
>> user/347bbab3d47d435cadf7ceea954b35d8 at wdz.de?anonymous&ep=signature>
>>
>>
>>
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