[ovs-dev] [PATCH v2] Make pid_exists() more robust against empty pid argument

Ben Pfaff blp at ovn.org
Thu Aug 29 14:46:18 UTC 2019


On Tue, Aug 27, 2019 at 02:43:21PM +0300, Ilya Maximets wrote:
> On 14.08.2019 18:47, Michele Baldessari wrote:
> > In some of our destructive testing of ovn-dbs inside containers managed
> > by pacemaker we reached a situation where /var/run/openvswitch had
> > empty .pid files. The current code does not deal well with them
> > and pidfile_is_running() returns true in such a case and this confuses
> > the OCF resource agent.
> > 
> > - Before this change:
> > Inside a container run:
> >   killall ovsdb-server;
> >   echo -n '' > /var/run/openvswitch/ovnnb_db.pid; echo -n '' > /var/run/openvswitch/ovnsb_db.pid
> 
> What about whitespaces?
> I mean, if you'll  write ' ' instead of '', the check 'test -n "$1"'
> will succeed and the test will fail.

I think that is OK, because test -d "/proc/ " will also fail.

> To handle this case we need to trim off whitespaces by the 'tr' utility
> or change the proc checker to something like 'test -f /proc/"$1"/status'.

I guess to be absolutely certain we'd need something like

case $1 in
  '')       false ;;    # Reject empty string
  *[!0-9]*) false ;;    # Reject anything with non-digits
  *)        test -d /proc/$1 ;;
esac

Anyway, I think that this is an improvement, so I applied it to master
and backported it.


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