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SELinux is preventing systemctl from write access on the chr_file kmsg. ***** Plugin catchall (100. confidence) suggests ************************** If you believe that systemctl should be allowed write access on the kmsg chr_file by default. Then you should report this as a bug. You can generate a local policy module to allow this access. Do allow this access for now by executing: # ausearch -c 'systemctl' --raw | audit2allow -M my-systemctl # semodule -i my-systemctl.pp Additional Information: Source Context system_u:system_r:logrotate_t:s0-s0:c0.c1023 Target Context system_u:object_r:kmsg_device_t:s0 Target Objects kmsg [ chr_file ] Source systemctl Source Path systemctl Port <Unknown> Host redacted.example.com Source RPM Packages systemd-219-30.el7_3.6.x86_64 Target RPM Packages Policy RPM selinux-policy-3.13.1-102.el7_3.13.noarch Selinux Enabled True Policy Type targeted Enforcing Mode Enforcing Host Name redacted.example.com Platform Linux redacted.example.com 3.10.0-514.6.1.el7.x86_64 #1 SMP Wed Jan 18 13:06:36 UTC 2017 x86_64 x86_64 Alert Count 2 First Seen 2017-01-22 04:07:02 EST Last Seen 2017-01-23 03:06:02 EST Local ID 935b4524-e165-488d-960e-f7164a945cab Raw Audit Messages type=AVC msg=audit(1485158762.113:3136): avc: denied { write } for pid=16459 comm="systemctl" name="kmsg" dev="devtmpfs" ino=1034 scontext=system_u:system_r:logrotate_t:s0-s0:c0.c1023 tcontext=system_u:object_r:kmsg_device_t:s0 tclass=chr_file type=SYSCALL msg=audit(1485158762.113:3136): arch=x86_64 syscall=open success=no exit=EACCES a0=7fd9ec6dc17f a1=80101 a2=ffffffff a3=7fd9eb7357b8 items=0 ppid=16458 pid=16459 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=414 comm=systemctl exe=/usr/bin/systemctl subj=system_u:system_r:logrotate_t:s0-s0:c0.c1023 key=(null) Hash: systemctl,logrotate_t,kmsg_device_t,chr_file,write In case it's relevant: $ rpm -q logrotate logrotate-3.8.6-12.el7.x86_64
Was the kernel executed with some special logging parameters? # cat /proc/cmdline
Yes indeed: # cat /proc/cmdline BOOT_IMAGE=/vmlinuz-3.10.0-514.6.1.el7.x86_64 root=/dev/mapper/vg1-lv1 ro rd.lvm.lv=vg1/lv1 rd.shell=0 rd.lvm.lv=vg1/lv3 crashkernel=auto printk.time=0 biosdevname=0 rhgb quiet LANG=en_US.UTF-8 systemd.log_level=debug systemd.log_target=kmsg We were previously running kernel 3.10.0-327.36.3.el7.x86_64, and those last two parameters appear to be new additions since upgrading to 3.10.0-514.6.1.el7.x86_64. It's not clear to me if those are now the intended defaults for RHEL 7.3? We certainly didn't intentionally add them.
Ah ok, looks like that happened because we got hit (again) with Bug 1285601, which resulted in the "...with debugging" kernel incorrectly being made the default boot target in the grub menu. So ok, we know how to work around that. But that's actually a little beside the point for the current bug report; this logging configuration SHOULD work without an SELinux denial, correct? Which implies that selinux-policy may need to be adjusted to allow this.
I can imagine that a lot of SELinux domains will try to write to /dev/kmsg. Could we solve that problem via a new boolean?
Milos, You mean some boolean that all domains can write to /dev/kmsg ? Thanks.
Yes.
Agree with Milos. Adding new boolean.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2017:1861