[Dnsmasq-discuss] Core dumped when reloading

[Petr Menšík]

There were found few known regressions in 2.86 release. Could you try
latest test release of version 2.87, if that crash would still occur?
Multiple of issues were fixed already.

On 5/7/22 13:16, 韩冰 wrote:
> Hello everyone,
> I found a core dump issue when I use dnsmasq as a DHCP server (Version
> 2.86, running on Linux). My setup and reproduction step is as follows.
> Dnsmasq main config
>
>     # Common Configure
>     pid-file=/var/run/dnsmasq.pid
>     log-facility=/var/log/dnsmasq.log
>     user=root
>     group=root
>     interface=eth0
>
>     # DNS Server Configure
>     no-hosts
>     no-resolv
>     log-queries=extra
>     port=53
>
>     # DHCP Server Configure
>     log-dhcp
>     dhcp-range=172.17.12.128,static,255.255.255.192 # Change the
>     network address and subnet mask.
>     dhcp-hostsfile=/etc/dnsmasq/dhcp-hosts
>     dhcp-optsfile=/etc/dnsmasq/dhcp-options
>     dhcp-vendorclass=set:pxe-bios-x86,PXEClient:Arch:00000
>     dhcp-vendorclass=set:pxe-uefi-amd64,PXEClient:Arch:00007
>     dhcp-vendorclass=set:pxe-uefi-amd64,PXEClient:Arch:00009
>     dhcp-boot=tag:pxe-bios-x86,pxelinux.0,pxeserver
>     dhcp-boot=tag:pxe-uefi-amd64,bootnetx64.efi,pxeserver
>     dhcp-ignore=tag:!known
>
> External DHCP host file
>
>     08:c0:eb:cb:MM:NN,id:*,set:mytag,172.17.12.XXX,XXX-01,5m 
>
> External DHCP options file
>
>     tag:mytag,option:netmask,255.255.255.128
>     tag:mytag,option:router,172.17.12.190
>     tag:mytag,option:dns-server,172.16.0.XXX
>     tag:mytag,option:ntp-server,172.16.0.XXX
>     tag:mytag,option:domain-name,mydomain
>
> Reproduction step is 
> First start dnsmasq with the config shown above, 
> Then use 08:c0:eb:cb:MM:NN to obtain an IP address from dnsmasq server.
> After we can see lease of 08:c0:eb:cb:MM:NN in dnsmasq.leases, send
> signal HUP to dnsmasq,
> Now I got dnsmasq core dumped and traceback is following
>
>     #0  __GI_raise (sig=sig at entry=6) at
>     ../sysdeps/unix/sysv/linux/raise.c:50
>     #1  0x00007f858837f535 in __GI_abort () at abort.c:79
>     #2  0x00007f85883d6518 in __libc_message
>     (action=action at entry=do_abort, fmt=fmt at entry=0x7f85884e028d "%s\n")
>         at ../sysdeps/posix/libc_fatal.c:181
>     #3  0x00007f85883dcc3a in malloc_printerr
>     (str=str at entry=0x7f85884e1fe0 "double free or corruption (out)")
>     at malloc.c:5359
>     #4  0x00007f85883de770 in _int_free (av=0x7f8588517c40
>     <main_arena>, p=0x7ffd7d6e79a0, have_lock=<optimized out>) at
>     malloc.c:4321
>     #5  0x0000000000410187 in dhcp_netid_free (nid=0x7ffd7d6e79b0) at
>     option.c:1019
>     #6  0x0000000000410258 in dhcp_netid_list_free (netid=0x0) at
>     option.c:1050
>     #7  0x00000000004102c9 in dhcp_config_free (config=0x2273950) at
>     option.c:1068
>     #8  0x000000000041c313 in clear_dynamic_conf () at option.c:5186
>     #9  0x000000000041c3bd in reread_dhcp () at option.c:5219
>     #10 0x0000000000428a11 in clear_cache_and_reload (now=1650633404)
>     at dnsmasq.c:1694
>     #11 0x0000000000428303 in async_event (pipe=10, now=1650633404) at
>     dnsmasq.c:1450
>     #12 0x0000000000427cf4 in main (argc=3, argv=0x7ffd7d6e81a8) at
>     dnsmasq.c:1193
>
> It looks like there is some memory management issue about dhcp tag
> I found another related fact that if I just start dnsmasq and reload
> it, or dnsmasq only receive dhcp packet from UNKNOWN mac address and
> reload it, dnsmasq will NOT core dumped when reloading, so I guess
> that the issue maybe related to progress of DHCP packet
> That is all about I found about core dumped issue when reloading, I'm
> looking forward for someone found similar problem or have idea about
> this issue
>
> Thanks
> Han Bing
>
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-- 
Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemensik at redhat.com
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB
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