[libvirt PATCH 12/17] util: Try to get limits from /proc

[Andrea Bolognani]

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.

> > +    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.

> > +    /* 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