Arch Linux

benalexau

Member

Registered: 2013-10-10

Posts: 19

[SOLVED] dhcpcd 7.2.1 coredump randomly with wired connection

I have a Supermicro server with a Cat 6 connection to an Arris CM8200 cable modem. The server uses netctl to DHCP acquire an IPv4 address from the cable modem. Every 24-48 hours journalctl shows dhcpcd 7.2.1 coredumps with:

#0  0x00007ffae9c6182f raise (libc.so.6)
#1  0x00007ffae9c4c672 abort (libc.so.6)
#2  0x00007ffae9ca3e78 __libc_message (libc.so.6)
#3  0x00007ffae9d35855 __GI___fortify_fail_abort (libc.so.6)
#4  0x00007ffae9d35885 __fortify_fail (libc.so.6)
#5  0x00007ffae9d34074 __chk_fail (libc.so.6)
#6  0x00005589b56412c7 arp_read (dhcpcd)
#7  0x00005589b562772b eloop_start (dhcpcd)
#8  0x00005589b5621d2d main (dhcpcd)
#9  0x00007ffae9c4dce3 __libc_start_main (libc.so.6)
#10 0x00005589b562247e _start (dhcpcd)

Issue remains despite pacman -Syu to the latest and multiple reboots. Workaround implemented by cron using pgrep to detect dhcpcd absence and then netctl stop and start of the interface.

The issue never occurred with the prior cable modem, which was replaced 4 days ago. However the new cable modem is the only option.

Any suggestions appreciated.

Last edited by benalexau (2019-06-19 07:39:10)

seth

Member

Registered: 2012-09-03

Posts: 50,957

Re: [SOLVED] dhcpcd 7.2.1 coredump randomly with wired connection

That's a buffer overflow or other bad memory access in arp_read (so the different modem makes some sense).
There's nothing obvious in the dhcpcd code, so you'll have to build dhcpcd debug enabled and unstripped to get more details where exactly it crashes (and with what values, though there's probably some garbage is the ARP response)

Ideally file a bug against dhcpcd upstream w/ the enhanced backtrace.

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rsmarples

Member

Registered: 2009-05-12

Posts: 287

Re: [SOLVED] dhcpcd 7.2.1 coredump randomly with wired connection

There was nothing obvious for sure, but a fellow dhcpcd user identified the issue and a fix was comitted last month here:
https://roy.marples.name/cgit/dhcpcd.gi … e5fa683a7e

The issue itself was extremely hard to spot and very hard to replicate.
This was fixed in dhcpcd-7.2.2 which has been in Arch testing for a month now - maybe someone needs to pester a maintainer to move it to stable?

benalexau

Member

Registered: 2013-10-10

Posts: 19

Re: [SOLVED] dhcpcd 7.2.1 coredump randomly with wired connection

Thanks Roy for replying and having already made a release with this resolved!

I am unsure how to pester a maintainer but at least it's fixed and the workaround cron job keeps it from being a major issue in the interim.

Thanks again.

rsmarples

Member

Registered: 2009-05-12

Posts: 287

Re: [SOLVED] dhcpcd 7.2.1 coredump randomly with wired connection

For reference, dhcpcd-7.2.2 has been moved to stable now.