Description of problem: Latest Fedora 26 and 27 kernel updates break core dumping for processes in systemd units. On 4.13.16-302.fc27.x86_64 everything works as intended, on 4.14.3-300.fc27.x86_64 not any more. Version-Release number of selected component (if applicable): kernel-4.14.5-300.fc27.x86_64 How reproducible: Always Steps to Reproduce: 1. journalctl -f 2. systemctl start systemd-hostnamed 3. pkill -e -SEGV systemd-hostnam Actual results: journal shows no backtrace and coredumpctl shows no coredump. Expected results: Journal shows something like "Process 3271 (systemd-hostnam) of user 0 dumped core." and a backtrace. Additional info: * This works for "default namespace" processes, like so: sleep 100 & pkill -e -SEGV sleep Then you get a core dump. * This works once you disable SELinux (setenforce 0). However, there are no SELinux violations logged. * This is not dependent on systemd-coredump. You can do # cat <<EOF > /tmp/core.sh #!/bin/sh echo "invoked core dump: $@" >> /tmp/log cat > /tmp/core echo "invoked core dump: $@ DONE" >> /tmp/log EOF # chmod 755 /tmp/core.sh # echo "|/tmp/core.sh %P %u" > /proc/sys/kernel/core_pattern and then run the above expriments again with the same result: core is dumped for sleep but not for systemd-hostnamed. So this is not an issue in systemd-coredump.
The "in namespaces" part could be premature -- maybe it's also just a matter of core dump size. https://www.spinics.net/lists/kernel/msg2672293.html could be related (thanks to "grift" for pointing out).
If you can do a bisection, that's going to be the fastest way to find what broke. Also, please test on a rawhide kernel to see if the problem is present there as well.
F27 got updated from 4.14.3 to 4.14.5-300.fc27.x86_64, confirmed that the issue still exists with that.
Confirmed with kernel 4.15.0-0.rc3.git0.1.fc28.x86_64 from rawhide (https://fedoraproject.org/wiki/RawhideKernelNodebug), same behaviour.
Okay, I did a bisect and think I got a bad commit git bisect start 'v4.14' 'v4.13' # good: [15d8ffc96464f6571ecf22043c45fad659f11bdd] Merge tag 'mmc-v4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc git bisect good 15d8ffc96464f6571ecf22043c45fad659f11bdd # bad: [e90937e756938f03d37d4cae7c82316a3a425944] Merge tag 'armsoc-devicetree' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc git bisect bad e90937e756938f03d37d4cae7c82316a3a425944 # bad: [fd1d362600e2d2edb6262d8e05661424c1a315bf] ARM: implement memset32 & memset64 git bisect bad fd1d362600e2d2edb6262d8e05661424c1a315bf # good: [c0da4fa0d1a54495d6055c009ac46b76d1da2c86] Merge tag 'media/v4.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media git bisect good c0da4fa0d1a54495d6055c009ac46b76d1da2c86 # good: [44ccba3f7b230af1bd7ebe173cbf5803df1df486] Merge tag 'gcc-plugins-v4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux git bisect good 44ccba3f7b230af1bd7ebe173cbf5803df1df486 # good: [2877cbffb79ed121a6bcc5edbe629d3aba36cd29] scsi: lpfc: Fix loop mode target discovery git bisect good 2877cbffb79ed121a6bcc5edbe629d3aba36cd29 # good: [a45a1f3614182267803baadba657b59e2ddc0545] scsi: scsi-mq: Always unprepare before requeuing a request git bisect good a45a1f3614182267803baadba657b59e2ddc0545 # bad: [8135d8926c08e553e39b0b040c6d01f0daef0676] mm: memory_hotplug: memory hotremove supports thp migration git bisect bad 8135d8926c08e553e39b0b040c6d01f0daef0676 # bad: [0fb02e718f5fd88b175387bc2a9313b27609f0da] Merge tag 'audit-pr-20170907' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit git bisect bad 0fb02e718f5fd88b175387bc2a9313b27609f0da # bad: [e37fdb785a5f95ecadf43b773c97f676500ac7b8] exec: Use secureexec for setting dumpability git bisect bad e37fdb785a5f95ecadf43b773c97f676500ac7b8 # good: [62874c3adf709b884ceb0c61c35ab3794b3b0e95] selinux: Refactor to remove bprm_secureexec hook git bisect good 62874c3adf709b884ceb0c61c35ab3794b3b0e95 # good: [46d98eb4e1d2bc225f661879e0e157a952107598] commoncap: Refactor to remove bprm_secureexec hook git bisect good 46d98eb4e1d2bc225f661879e0e157a952107598 # good: [2af622802696e1dbe28d81c8ea6355dc30800396] LSM: drop bprm_secureexec hook git bisect good 2af622802696e1dbe28d81c8ea6355dc30800396 # first bad commit: [e37fdb785a5f95ecadf43b773c97f676500ac7b8] exec: Use secureexec for setting dumpability It didn't revert cleanly but reverting several other dependent commits it did work. I'll send an e-mail to the author.
There was a revert on part of the patch https://marc.info/?l=linux-kernel&m=151493531216097 , please test this if you get a chance
Confirming that this works again on Fedora 27 kernel 4.14.16-300.fc27.x86_64. Thanks!