Re: bin/57952 (dhcpcd(8) inexplicably terminated in the night)

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

The following reply was made to PR bin/57952; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: Roy Marples <roy%marples.name@localhost>
Cc: gnats-bugs%NetBSD.org@localhost,
	Martin Husemann <martin%duskware.de@localhost>,
	gnats-admin%NetBSD.org@localhost,
	netbsd-bugs%NetBSD.org@localhost
Subject: Re: bin/57952 (dhcpcd(8) inexplicably terminated in the night)
Date: Sat, 24 Feb 2024 00:48:47 +0000

 > Date: Fri, 23 Feb 2024 23:29:05 +0000
 > From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
 >=20
 > So I infer that the network proxy must have crashed, in my original
 > case.  But I don't see how to trigger a core dump.
 
 Just in case somehow there's set-user/group-id processes involved, I
 also tried:
 
 1. make /var/chroot/dhcpcd/var/crash owned by _dhcpcd:_dhcpcd
 2. add `kern.coredump.setid.dump=3D1' to /etc/modules.conf
 3. reboot
 4. kill -ABRT manager
 
 I got a zero-length core file and a console message;
 
 [ 1251.6878114] pid 6079 (dhcpcd): system write of 64@0xffffc000b03a79c0 at=
  0 failed: 27
 
 I tried unlimiting the file size with
 
 # sysctl -w proc.$pid.rlimit.filesize.hard=3Dunlimited
 # sysctl -w proc.$pid.rlimit.filesize.soft=3Dunlimited
 
 and this time, kill -ABRT manager produced a core dump at
 /var/chroot/dhcpcd/var/crash/dhcpcd.core!
 
 So there's several issues:
 
 1. dhcpcd somehow gets the kern.coredump.setid treatment (which I
    thought was reserved for executables having the set-user/group-id
    bit set, and I don't see any evidence of that in dhcpcd)
 
 2. /var/crash doesn't exist under the chroot, /var/chroot/dhcpcd
 
 3. the filesize rlimit prevents the core dump too