Re: [PATCH] virtiofsd: Add `sigreturn` to the seccomp whitelist

[Dr. David Alan Gilbert]

* Marc Hartmayer (mhartmay@linux.ibm.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:
> 
> > * Marc Hartmayer (mhartmay@linux.ibm.com) wrote:
> >> The virtiofsd currently crashes on s390x. This is because of a
> >> `sigreturn` system call. See audit log below:
> >> 
> >> type=SECCOMP msg=audit(1669382477.611:459): auid=4294967295 uid=0 gid=0 
> >> ses=4294967295 subj=system_u:system_r:virtd_t:s0-s0:c0.c1023 pid=6649 
> >> comm="virtiofsd" exe="/usr/libexec/virtiofsd" sig=31 arch=80000016 
> >> syscall=119 compat=0 ip=0x3fff15f748a code=0x80000000AUID="unset" 
> >> UID="root" GID="root" ARCH=s390x SYSCALL=sigreturn
> >
> > I'm curious; doesn't that mean that some signal is being delivered and
> > you're returning?  Which one?
> 
> code=0x80000000 means that the seccomp action SECCOMP_RET_KILL_PROCESS
> is taken => process is killed by a SIGSYS signal (31) [1].
> 
> At least, that’s my understanding of this log message.
> 
> [1] https://man7.org/linux/man-pages/man2/seccomp.2.html

But isn't that the fallout rather than the cause ? i.e. seccomp
is sending a SIGSYS because the process used sigreturn, my question
is why did the process call sigreturn in the first place - it must
have received a signal to return from?

Dave

> […snip…]
> 
> > -- 
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> >
> -- 
> Kind regards / Beste Grüße
>    Marc Hartmayer
> 
> IBM Deutschland Research & Development GmbH
> Vorsitzender des Aufsichtsrats: Gregor Pillen 
> Geschäftsführung: David Faller
> Sitz der Gesellschaft: Böblingen
> Registergericht: Amtsgericht Stuttgart, HRB 243294
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK