On Thu, Dec 08, 2016 at 12:29:42PM -0800, Kees Cook wrote:
> On Thu, Dec 8, 2016 at 11:48 AM, Luis R. Rodriguez <mcg...@kernel.org> wrote:
> > kmod_concurrent is used as an atomic counter for enabling
> > the allowed limit of modprobe calls, provide wrappers for it
> > to enable this to be expanded on more easily. This will be done
> > later.
> >
> > Signed-off-by: Luis R. Rodriguez <mcg...@kernel.org>
> > ---
> > kernel/kmod.c | 27 +++++++++++++++++++++------
> > 1 file changed, 21 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/kmod.c b/kernel/kmod.c
> > index cb6f7ca7b8a5..049d7eabda38 100644
> > --- a/kernel/kmod.c
> > +++ b/kernel/kmod.c
> > @@ -44,6 +44,9 @@
> > #include <trace/events/module.h>
> >
> > extern int max_threads;
> > +
> > +static atomic_t kmod_concurrent = ATOMIC_INIT(0);
> > +
> > unsigned int max_modprobes;
> > module_param(max_modprobes, uint, 0644);
> > MODULE_PARM_DESC(max_modprobes, "Max number of allowed concurrent
> > modprobes");
> > @@ -108,6 +111,20 @@ static int call_modprobe(char *module_name, int wait)
> > return -ENOMEM;
> > }
> >
> > +static int kmod_umh_threads_get(void)
> > +{
> > + atomic_inc(&kmod_concurrent);
> > + if (atomic_read(&kmod_concurrent) < max_modprobes)
> > + return 0;
> > + atomic_dec(&kmod_concurrent);
> > + return -ENOMEM;
> > +}
> > +
> > +static void kmod_umh_threads_put(void)
> > +{
> > + atomic_dec(&kmod_concurrent);
> > +}
>
> Can you use a kref here instead? We're trying to kill raw use of
> atomic_t for reference counting...
That's a much broader functional change than I was looking for, but I am up for
it. Can you describe the benefit of using kref you expect or why this is an
ongoing crusade? Since its a larger functional change how about doing this
change later, and we can test impact with the tress test driver. In theory if
there are benefits can't we add a test case to prove the gains?
Luis
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