On 2025-10-13 10:41:06, Darrick J. Wong wrote:
> [yay, debian bugs aren't cc'ing linux-xfs consistently]

They try to, but fail because the (new) bug source address is not
subscribed to linux-xfs, and thus there is a bounce. I haven't had time
to report this, sorry.

> > I've struggled with this for a while because all my logs were spammed by
> > hundreds of lines of:
> > 
> > postfix/postdrop[37291]: warning: mail_queue_enter: create file 
> > maildrop/480926.37291: Permission denied
> > 
> > And it took me a long while to dig this down to xfs_scrub reporting.
> > Problem setup:
> > 
> > - mailer is postfix, which uses a setgid /usr/sbin/postdrop binary to
> >   write to /var/lib/postfix/maildrop (mode 0730, group postdrop)
> > - the systemd unit for the xfs_scrub reporting,
> >   /usr/lib/systemd/system/xfs_scrub_all_fail.service, contains:
> >   
> >   # xfs_scrub needs these privileges to run, and no others
> >   CapabilityBoundingSet=
> >   NoNewPrivileges=true
> > 
> > Together, this means that the script
> > (/usr/libexec/xfsprogs/xfs_scrub_fail) composes the email, and pipes it
> > to "/usr/sbin/sendmail -t -i", which in turn invokes the postdrop
> > binary, but which can't get the sgid bit. But since it calls sendmail
> 
> IOWs, postfix is installed and postdrop needs to be able to run as
> setgid, right?

Correct.

> Do you only need us to change the [email protected] file to have
> "NoNewPrivileges=false", or do you also need it to have
> "CapabilityBoundingSet=CAP_SETGID" ?
> 
> The systemd documentation implies that you only need
> NoNewPrivileges=false to run setgid programs, but I don't know for sure.
> I'll try to test this and report back, but it sounds like you're in a
> better position to say for sure that postfix works.  (I use msmtp)

I don't know either, but sometimes in the next weeks I hope to get time
to test it. I suspect CapabilityBoundingSet=CAP_SETGID is an improvement
on NoNewPrivileges=False, but not required.

> > repeatedly, I get for a few days, every hour, hundreds of flagged log
> > entries by logcheck.
> 
> Yikes.
> 
> > Now, the Trixie kernel seems to not support scrubbing anyway, so I can
> > simply disable this, but it would be better to fix this and do an update
> > (in trixe), otherwise the log spamming is really annoying.
> 
> Indeed.  Forky (assuming it gets 6.18/6.24) should have online fsck
> turned on since upstream changed the kconfig default.  Not that I have
> any idea how one gets kconfig options changed in Debian...

Me neither, but I assume a new setting would just get the default. Once
sid kernels get to 6.18, I can test in a VM.

thanks!

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