> On Jul 25, 2022, at 09:29, Felipe Gasper <felipe@xxxxxxxxxxxxxxxx> wrote: > > > >> On Jul 25, 2022, at 09:23, Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote: >> >> >> >>> On Jul 23, 2022, at 11:53 AM, Felipe Gasper <felipe@xxxxxxxxxxxxxxxx> wrote: >>> >>> Hello, >>> >>> I’m seeing two different behaviours between kernel NFS server versions in AlmaLinux 8 and Ubuntu 20. The following Perl demonstrates the issue: >>> >>> -------- >>> perl -MFile::Temp -Mautodie -Mstrict -e'my $fh = File::Temp::tempfile( DIR => "/the/nfs/mount" ); my $mailgid = getgrnam "mail"; my ($uid, $gid) = (getpwnam "bin")[2,3]; chown $uid, $gid, $fh; $) = "$gid $mailgid"; $> = $uid; chown -1, $mailgid, $fh' >>> -------- >>> >>> What this does, as root, is: >>> >>> 1) Creates a file under /mnt, then deletes it, leaving the Linux file descriptor open. >>> >>> 2) chowns the file to bin:bin. >>> >>> 3) Sets the process’s EUID & GUID to bin & bin/mail. >>> >>> 4) Does fchown( fd, -1, mailgid ). >>> >>> When the server is AlmaLinux 8, the above works. When the server is Ubuntu 20, it fails with EPERM. (The client is AlmaLinux 8 in both cases.) Both are configured identically. >> >> On each NFS sever, can you run 'uname -a' and show us the output? > > Ubuntu 20 (the “bad” one): > root@kvm-demo-support:~# uname -a > Linux kvm-demo-support 5.4.0-122-generic #138-Ubuntu SMP Wed Jun 22 15:00:31 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux > > AlmaLinux 8 (the “good” one): > [root@10-2-71-6 ~]# uname -a > Linux 10-2-71-6.cprapid.com 4.18.0-372.16.1.el8_6.x86_64 #1 SMP Wed Jul 13 03:56:16 EDT 2022 x86_64 x86_64 x86_64 GNU/Linux > >> >> On on the NFS client, can you show us the output of 'nfsstat -m' >> during each test run? > >> nfsstat -m > /mnt/phil from kvm-demo-support.dev.cpanel.net:/volumes/kvm-demo > Flags: rw,relatime,vers=4.2,rsize=262144,wsize=262144,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=10.2.65.75,local_lock=none,addr=10.0.32.83 > > /mnt/felipe from 10.2.71.6:/home > Flags: rw,relatime,vers=4.2,rsize=262144,wsize=262144,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=10.2.65.75,local_lock=none,addr=10.2.71.6 Update on this: it appears to have been a result of Ubuntu 20’s /etc/default/nfs-kernel-server’s containing `RPCMOUNTDOPTS="--manage-gids"`. Once I commented that line out the issue went away. I also confirmed that AlmaLinux 8 doesn’t enable `--manage-gids`. The varlink traffic in the Ubuntu server to/from rpc.mountd showed that it was asking systemd for the user’s groups and getting an empty response. Sorry for the noise, and thank you for your time. cheers, -Felipe
