On Mon, Mar 08, 2021 at 04:21:16PM +0100, Andrea Bolognani wrote:
> On Mon, 2021-03-08 at 10:50 +0000, Daniel P. Berrangé wrote:
> > On Fri, Mar 05, 2021 at 08:13:59PM +0100, Andrea Bolognani wrote:
> > > + if (!(label = virProcessLimitResourceToLabel(resource))) {
> > > + virReportError(VIR_ERR_INTERNAL_ERROR,
> > > + _("Unknown resource %d requested for process %lld"),
> > > + resource, (long long)pid);
> > > + return -1;
> >
> > Setting errors on -1
>
> This is only hit if virProcessGetLimitFromProc() has been asked to
> obtain limits for a resource it doesn't know how to fetch, which
> indicates a bug in libvirt and is thus reported as internal error.
The our coding standard is that we only call virReportError if the
caller is actually going to honour the errors.
>
> > > + procfile = g_strdup_printf("/proc/%lld/limits", (long long)pid);
> > > +
> > > + if (!g_file_get_contents(procfile, &buf, &len, NULL))
> > > + return -1;
> >
> > Not setting errors on -1
>
> This is simply "file couldn't be read", which would be the case on
> FreeBSD for example.
Right, but we *must* always be consistent in whether a method uses
virReportError or not. We have two code paths here returning -1,
and only one of which reports errors. Either all must report
errors, or none. Since the only caller is ignoring errors, then
it looks like none should report errors.
>
> > > + /* For whatever reason, using prlimit() on another process - even
> > > + * when it's just to obtain the current limit rather than changing
> > > + * it - requires CAP_SYS_RESOURCE, which we might not have in a
> > > + * containerized environment; on the other hand, no particular
> > > + * permission is needed to poke around /proc, so try that if going
> > > + * through the syscall didn't work */
> > > + if (virProcessGetLimitFromProc(pid, resource, old_limit) == 0)
> > > + return 0;
> >
> > This ought to be conditional for Linux only and error reporting needs
> > to be made consistent.
>
> The intent above was to have this fail quietly on non-Linux without
> adding checks for it, but sure I can have an actual stub on other
> platforms instead.
>
> --
> Andrea Bolognani / Red Hat / Virtualization
>
Regards,
Daniel
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