netdev - Re: [PATCH iproute2] testsuite: don't clobber /tmp

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Message-ID: <CAGnkfhyT0W=CYU8FJYrDtzqxtcHakO5CWx2qzLuWOXVj6dyKMA@mail.gmail.com>
Date:   Wed, 12 Jun 2019 18:04:21 +0200
From:   Matteo Croce <mcroce@...hat.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev <netdev@...r.kernel.org>, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH iproute2] testsuite: don't clobber /tmp

On Wed, Jun 12, 2019 at 5:55 PM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
> On Tue, 11 Jun 2019 20:03:26 +0200
> Matteo Croce <mcroce@...hat.com> wrote:
>
> > Even if not running the testsuite, every build will leave
> > a stale tc_testkenv.* file in the system temp directory.
> > Conditionally create the temp file only if we're running the testsuite.
> >
> > Signed-off-by: Matteo Croce <mcroce@...hat.com>
> > ---
> >  testsuite/Makefile | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/testsuite/Makefile b/testsuite/Makefile
> > index 7f247bbc..5353244b 100644
> > --- a/testsuite/Makefile
> > +++ b/testsuite/Makefile
> > @@ -14,7 +14,9 @@ TESTS_DIR := $(dir $(TESTS))
> >
> >  IPVERS := $(filter-out iproute2/Makefile,$(wildcard iproute2/*))
> >
> > -KENVFN := $(shell mktemp /tmp/tc_testkenv.XXXXXX)
> > +ifeq ($(MAKECMDGOALS),alltests)
> > +     KENVFN := $(shell mktemp /tmp/tc_testkenv.XXXXXX)
> > +endif
> >  ifneq (,$(wildcard /proc/config.gz))
> >       KCPATH := /proc/config.gz
> >  else
> > @@ -94,3 +96,4 @@ endif
> >               rm "$$TMP_ERR" "$$TMP_OUT"; \
> >               sudo dmesg > $(RESULTS_DIR)/$@...o.dmesg; \
> >       done
> > +     @$(RM) $(KENVFN)
>
> My concern is that there are several targets in this one Makefile.
>
> Why not use -u which gives name but does not create the file?

As the manpage says, this is unsafe, as a file with the same name can
be created in the meantime.
Another option is to run the mktemp in the target shell, but this will
require to escape every single end of line to make it a single shell
command, e.g.:

        KENVFN=$$(mktemp /tmp/tc_testkenv.XXXXXX); \
        if [ "$(KCPATH)" = "/proc/config.gz" ]; then \
                gunzip -c $(KCPATH) >$$KENVFN; \
        ...
        done ; \
        $(RM) $$KENVFN

-- 
Matteo Croce
per aspera ad upstream